/* ============================================================
   CodeFlow design system
   Identity: #0d1117 / #10141a canvas, #58a6ff accent, #1c2026 surfaces,
   Inter, Material Symbols. All sizes are rem so browser text zoom works.
   The one decoration is the program counter: .rail / .rail-node.
   ============================================================ */

/* Self-hosted fonts keep typography and symbol ligatures consistent offline. */
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 400 700;
  font-display: swap;
  src: url("/assets/fonts/inter-latin-ext.woff2") format("woff2");
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C4, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
@font-face {
  font-family: "Inter";
  font-style: normal;
  font-weight: 400 700;
  font-display: swap;
  src: url("/assets/fonts/inter-latin.woff2") format("woff2");
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
@font-face {
  font-family: "Material Symbols Outlined";
  font-style: normal;
  font-weight: 400;
  font-display: block;
  src: url("/assets/fonts/material-symbols-outlined.woff2") format("woff2");
}

:root {
  /* Palette */
  --bg: #0d1117;
  --bg-elevated: #10141a;
  --surface: #161b22;
  --surface-2: #1c2026;
  --surface-3: #232a33;
  --surface-4: #2c333d;
  --line: rgba(255, 255, 255, 0.07);
  --line-strong: rgba(255, 255, 255, 0.12);
  --accent: #58a6ff;
  --accent-ink: #9dc7ff;
  --accent-solid: #1f6feb;
  --accent-solid-hover: #2f81f7;
  --success: #3fb950;
  --success-ink: #7ee787;
  --danger: #f85149;
  --danger-ink: #ffa198;
  --warn: #d29922;
  --purple: #bc8cff;
  --text: #e6edf3;
  --text-muted: #9aa7b4;
  --text-faint: #8795a5; /* >=4.5:1 on #10141a, #161b22, #1c2026 and #232a33 */

  /* Type scale: 12 / 13 / 14 / 16 / 20 / 24 / 28 / 32 */
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --fs-12: 0.75rem;
  --fs-13: 0.8125rem;
  --fs-14: 0.875rem;
  --fs-16: 1rem;
  --fs-20: 1.25rem;
  --fs-24: 1.5rem;
  --fs-28: 1.75rem;
  --fs-32: 2rem;

  /* Space */
  --s-1: 0.25rem;
  --s-2: 0.5rem;
  --s-3: 0.75rem;
  --s-4: 1rem;
  --s-5: 1.25rem;
  --s-6: 1.5rem;
  --s-8: 2rem;
  --s-10: 2.5rem;

  /* Shape: controls 8px, panels 12px, pills only for the XP chip and filter chips */
  --r-sm: 0.5rem;
  --r-md: 0.75rem;
  --r-lg: 0.75rem;
  --r-pill: 999px;
  --shadow-2: 0 8px 24px rgba(0, 0, 0, 0.45);
  --shadow-3: 0 24px 64px rgba(0, 0, 0, 0.6);

  /* Layout */
  --sidebar-w: 15.5rem;
  --topbar-h: 3.75rem;
  --content-max: 88rem;
  --touch: 2.75rem;
  --ease: 140ms ease;
}

/* Light appearance keeps the same blue identity with a quieter neutral canvas. */
:root[data-theme="light"] {
  --bg: #eef2f6;
  --bg-elevated: #f8fafc;
  --surface: #ffffff;
  --surface-2: #f1f4f8;
  --surface-3: #e8edf3;
  --surface-4: #dbe2ea;
  --line: rgba(20, 31, 43, 0.09);
  --line-strong: rgba(20, 31, 43, 0.16);
  --accent: #0969da;
  --accent-ink: #0550ae;
  --accent-solid: #0969da;
  --accent-solid-hover: #0550ae;
  --success: #1a7f37;
  --success-ink: #116329;
  --danger: #cf222e;
  --danger-ink: #a40e26;
  --warn: #9a6700;
  --purple: #8250df;
  --text: #1f2328;
  --text-muted: #59636e;
  --text-faint: #6b7682;
  --shadow-2: 0 8px 24px rgba(20, 31, 43, 0.12);
  --shadow-3: 0 24px 64px rgba(20, 31, 43, 0.18);
  color-scheme: light;
}
:root[data-theme="dark"] { color-scheme: dark; }

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; }

html, body {
  height: 100%;
  margin: 0;
  background: var(--bg-elevated);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: var(--fs-14);
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
html { font-size: 100%; }

body { overflow: hidden; }
html.modal-open, body.modal-open { overflow: hidden !important; }

h1, h2, h3, h4 { margin: 0; font-weight: 600; letter-spacing: -0.01em; line-height: 1.3; }
p { margin: 0; }
button, input, select, textarea { font: inherit; color: inherit; }
code, pre { font-family: var(--font-mono); font-variant-ligatures: none; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: var(--r-sm);
}
::selection { background: rgba(88, 166, 255, 0.28); }

.material-symbols-outlined {
  font-family: "Material Symbols Outlined", sans-serif;
  font-weight: normal;
  font-style: normal;
  font-size: 1.25rem;
  line-height: 1;
  letter-spacing: normal;
  display: inline-block;
  white-space: nowrap;
  direction: ltr;
  font-variation-settings: 'FILL' 0, 'wght' 400, 'GRAD' 0, 'opsz' 24;
  font-feature-settings: 'liga';
}

/* ---------- Utilities ---------- */
.muted { color: var(--text-muted); font-size: var(--fs-13); }
.faint { color: var(--text-faint); font-size: var(--fs-12); }
.row { display: flex; align-items: center; gap: var(--s-2); }
.row-between { display: flex; align-items: center; justify-content: space-between; gap: var(--s-3); }
.wrap { flex-wrap: wrap; }
.stack { display: flex; flex-direction: column; gap: var(--s-3); }
.center { text-align: center; }
.hidden, [hidden] { display: none !important; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0;
}
.mobile-only { display: none; }

/* ============================================================
   Shell
   ============================================================ */
.app-shell { display: flex; width: 100%; height: 100vh; height: 100dvh; overflow: hidden; }

.app-main { flex: 1 1 auto; min-width: 0; display: flex; flex-direction: column; overflow: hidden; }

.stitch-sidebar.app-sidebar {
  width: var(--sidebar-w);
  flex: 0 0 var(--sidebar-w);
  display: flex;
  flex-direction: column;
  background: var(--bg-elevated);
  border-right: 1px solid var(--line);
  z-index: 40;
}

.sidebar-brand {
  display: flex; align-items: center; gap: var(--s-2);
  height: var(--topbar-h); flex: 0 0 var(--topbar-h);
  padding: 0 var(--s-5);
  border-bottom: 1px solid var(--line);
  font-size: var(--fs-16); font-weight: 700; letter-spacing: -0.01em;
}
.sidebar-brand .material-symbols-outlined { color: var(--accent); font-size: 1.3125rem; }

.sidebar-nav {
  flex: 1 1 auto; min-height: 0; overflow-y: auto;
  padding: var(--s-3) var(--s-2) var(--s-4);
  display: flex; flex-direction: column; gap: 2px;
}
.nav-label {
  font-size: var(--fs-12); font-weight: 600; letter-spacing: 0.08em;
  color: var(--text-faint); text-transform: uppercase;
  padding: var(--s-4) var(--s-3) var(--s-1);
}
.nav-label:first-child { padding-top: var(--s-1); }

.nav-item {
  display: flex; align-items: center; gap: 0.625rem;
  width: 100%; min-height: 2.5rem;
  padding: 0.4375rem 0.625rem;
  border: 0; border-radius: var(--r-sm);
  background: transparent;
  color: var(--text-muted);
  font-size: var(--fs-14); font-weight: 500;
  text-align: left; cursor: pointer;
  transition: background var(--ease), color var(--ease);
}
.nav-item .material-symbols-outlined { font-size: 1.125rem; color: inherit; opacity: 0.9; }
.nav-item:hover { background: rgba(255, 255, 255, 0.04); color: var(--text); }
.nav-item.active { background: rgba(88, 166, 255, 0.12); color: var(--accent-ink); }
.nav-item.active .material-symbols-outlined { color: var(--accent); }

.sidebar-progress { padding: var(--s-3) var(--s-4) var(--s-4); border-top: 1px solid var(--line); }
.sidebar-label { font-size: var(--fs-13); font-weight: 600; color: var(--text-muted); }
.sidebar-value { font-size: var(--fs-13); font-weight: 600; color: var(--text); }
.sidebar-sub { font-size: var(--fs-12); color: var(--text-faint); margin: 0.25rem 0 0; }
.sidebar-progress .progress-bar { margin-top: var(--s-2); }

/* Topbar */
.stitch-header.app-topbar {
  height: var(--topbar-h); flex: 0 0 var(--topbar-h);
  display: flex; align-items: center; justify-content: space-between; gap: var(--s-3);
  padding: 0 var(--s-6);
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--line);
}
.brand { display: none; align-items: center; gap: var(--s-2); font-size: var(--fs-16); font-weight: 700; letter-spacing: -0.01em; white-space: nowrap; }
.brand .material-symbols-outlined { color: var(--accent); font-size: 1.3125rem; }
.page-title {
  font-size: var(--fs-16); font-weight: 600;
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.xp-chip {
  display: inline-flex; align-items: center;
  font-size: var(--fs-12); font-weight: 600;
  color: var(--success-ink);
  background: rgba(63, 185, 80, 0.1);
  border: 1px solid rgba(63, 185, 80, 0.25);
  padding: 0.1875rem 0.625rem; border-radius: var(--r-pill);
  white-space: nowrap;
}

.icon-button {
  display: inline-grid; place-items: center;
  width: 2.25rem; height: 2.25rem;
  border: 1px solid transparent; border-radius: var(--r-sm);
  background: transparent; color: var(--text-muted);
  cursor: pointer; transition: background var(--ease), color var(--ease);
}
.icon-button:hover { background: rgba(255, 255, 255, 0.06); color: var(--text); }
.icon-button .material-symbols-outlined { font-size: 1.1875rem; }
.icon-button.mobile-only { display: none; }

/* Screens */
.screen-container { flex: 1 1 auto; min-height: 0; position: relative; overflow: hidden; }
.screen { display: none; flex-direction: column; width: 100%; height: 100%; min-height: 0; outline: none; }
.screen.active { display: flex; }
.screen-scroll {
  flex: 1 1 auto; min-height: 0;
  overflow-y: auto; overflow-x: hidden;
  overscroll-behavior: contain;
  scrollbar-gutter: auto;
}
.screen-inner { width: 100%; max-width: var(--content-max); margin: 0 auto; padding: clamp(1.5rem, 2.8vw, 3rem) clamp(1.5rem, 3.1vw, 3.5rem) 4rem; }

/* Page header */
.screen-heading {
  display: flex; align-items: flex-end; justify-content: space-between;
  gap: var(--s-4); flex-wrap: wrap;
  margin-bottom: var(--s-6);
}
.eyebrow { font-size: var(--fs-13); font-weight: 500; color: var(--text-muted); margin: 0 0 var(--s-2); }
.screen-title { font-size: var(--fs-28); font-weight: 600; color: var(--text); margin: 0; letter-spacing: -0.01em; line-height: 1.2; }
.screen-subtitle { font-size: var(--fs-14); color: var(--text-muted); margin: var(--s-2) 0 0; max-width: 70ch; }

/* ============================================================
   Components
   ============================================================ */

.card-title { font-size: var(--fs-14); font-weight: 600; margin: 0 0 var(--s-2); color: var(--text); }

/* Buttons: solid primary (one per region), outline secondary, text tertiary */
.stitch-btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 0.4375rem;
  min-height: 2.5rem; padding: 0.5rem 1rem;
  border: 1px solid transparent; border-radius: var(--r-sm);
  background: var(--accent-solid); color: #fff;
  font-size: var(--fs-14); font-weight: 600; line-height: 1.2;
  cursor: pointer; white-space: nowrap;
  transition: background var(--ease), border-color var(--ease), color var(--ease);
}
.stitch-btn:hover { background: var(--accent-solid-hover); text-decoration: none; }
.stitch-btn:disabled {
  background: var(--surface-3); color: var(--text-faint);
  border-color: var(--line); cursor: not-allowed;
}
.stitch-btn .material-symbols-outlined { font-size: 1.0625rem; }
.stitch-btn.secondary { background: transparent; color: var(--text); border-color: var(--line-strong); }
.stitch-btn.secondary:hover { background: rgba(255, 255, 255, 0.05); border-color: rgba(255, 255, 255, 0.24); }
.stitch-btn.danger { background: rgba(248, 81, 73, 0.14); color: var(--danger-ink); border-color: rgba(248, 81, 73, 0.35); }
.stitch-btn.danger:hover { background: rgba(248, 81, 73, 0.22); }
.button-row { display: flex; flex-wrap: wrap; align-items: center; gap: var(--s-2); }

.text-btn {
  display: inline-flex; align-items: center; gap: 0.25rem;
  min-height: 2.25rem; padding: 0 var(--s-2);
  border: 0; border-radius: var(--r-sm); background: transparent;
  color: var(--accent-ink); font-size: var(--fs-13); font-weight: 500;
  cursor: pointer; white-space: nowrap;
}
.text-btn:hover { background: rgba(255, 255, 255, 0.05); text-decoration: none; color: var(--text); }
.text-btn .material-symbols-outlined { font-size: 1.0625rem; }

/* Badges */
.badge {
  display: inline-flex; align-items: center; gap: 4px;
  font-size: var(--fs-12); font-weight: 600;
  padding: 0.125rem 0.5rem; border-radius: var(--r-sm);
  background: rgba(88, 166, 255, 0.12); color: var(--accent-ink);
  border: 1px solid rgba(88, 166, 255, 0.2);
  white-space: nowrap;
}
.badge.success { background: rgba(63, 185, 80, 0.12); color: var(--success-ink); border-color: rgba(63, 185, 80, 0.28); }
.badge.warn { background: rgba(210, 153, 34, 0.12); color: #e3b341; border-color: rgba(210, 153, 34, 0.3); }
.badge.danger { background: rgba(248, 81, 73, 0.12); color: var(--danger-ink); border-color: rgba(248, 81, 73, 0.3); }

/* Filter chips (one of two pill uses) */
.filter-row { display: flex; flex-wrap: wrap; gap: var(--s-2); }
.filter-chip {
  min-height: 2rem; padding: 0.25rem 0.875rem;
  border: 1px solid var(--line-strong); border-radius: var(--r-pill);
  background: transparent; color: var(--text-muted);
  font-size: var(--fs-13); font-weight: 500; cursor: pointer;
  white-space: nowrap;
  transition: background var(--ease), color var(--ease), border-color var(--ease);
}
.filter-chip:hover { background: rgba(255, 255, 255, 0.05); color: var(--text); }
.filter-chip.active { background: rgba(88, 166, 255, 0.14); color: var(--accent-ink); border-color: rgba(88, 166, 255, 0.45); }
.filter-chip span { color: var(--text-faint); font-weight: 400; margin-left: 0.25rem; }
.filter-chip.active span { color: inherit; opacity: 0.8; }

/* Form controls */
.field-label {
  display: block; font-size: var(--fs-13); font-weight: 500;
  color: var(--text-muted); margin: 0 0 0.375rem;
}
.input, .select, .text-input, .code-textarea {
  width: 100%; min-height: 2.5rem;
  padding: 0.4375rem 0.75rem;
  background: var(--bg-elevated);
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--text); font-size: var(--fs-14);
  transition: border-color var(--ease), box-shadow var(--ease);
}
.input::placeholder, .text-input::placeholder::placeholder, .code-textarea::placeholder { color: var(--text-faint); }
.input:focus, .select:focus, .text-input:focus, .code-textarea:focus:focus {
  outline: none; border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.2);
}
.code-textarea { min-height: 15rem; font-family: var(--font-mono); font-size: var(--fs-13); line-height: 1.6; resize: vertical; }
.field { margin-bottom: var(--s-4); }

/* Progress bar */
.progress-bar { height: 0.25rem; background: var(--surface-4); border-radius: 2px; overflow: hidden; }
.progress-fill { height: 100%; background: var(--accent); border-radius: 2px; }
.progress-fill.success { background: var(--success); }

/* ============================================================
   The program counter: .rail / .rail-node
   A debugger's current-line marker on a thin vertical rail.
   Hollow node = upcoming, filled = done, accent arrow = current.
   Reused later for the visualizer's current line and the Quest map.
   Markup: <ol class="rail"><li class="rail-row"><span class="rail-node done" aria-hidden="true"></span>...</li></ol>
   ============================================================ */
.rail {
  --rail-pad: 0.5rem;
  --rail-lh: 1.375rem;
  --rail-center: calc(var(--rail-pad) + var(--rail-lh) / 2);
  list-style: none; margin: 0; padding: 0;
}
.rail-row {
  position: relative;
  padding: var(--rail-pad) 0 var(--rail-pad) 2rem;
  line-height: var(--rail-lh);
  border-radius: var(--r-sm);
}
.rail-row::before { /* the rail */
  content: ""; position: absolute; left: 0.75rem; top: 0; bottom: 0; width: 1px;
  background: var(--line-strong);
}
.rail-row.is-first::before { top: var(--rail-center); }
.rail-row.is-last::before { bottom: auto; height: var(--rail-center); }
.rail-row.is-first.is-last::before { display: none; }
.rail-node {
  position: absolute; left: 0.75rem; top: var(--rail-center);
  width: 0.75rem; height: 0.75rem;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  background: var(--bg); border: 1.5px solid var(--text-faint);
}
.rail-node.done { background: var(--text-muted); border-color: var(--text-muted); }
.rail-node.current {
  width: 0.875rem; height: 1rem; border: 0; border-radius: 0;
  background: var(--accent);
  clip-path: polygon(0 0, 100% 50%, 0 100%);
  transform: translate(-38%, -50%);
}
@media (forced-colors: active) {
  .rail-node.current { forced-color-adjust: none; background: Highlight; }
  .rail-node.done { forced-color-adjust: none; background: CanvasText; }
}
.rail-link { color: var(--text); font-weight: 500; }
.rail-link::after { content: ""; position: absolute; inset: 0; border-radius: var(--r-sm); } /* whole row is the link */
.rail-link:hover { text-decoration: none; }
.rail-link:focus-visible { outline: none; }
.rail-link:focus-visible::after { outline: 2px solid var(--accent); outline-offset: -2px; }
.rail-row:hover { background: rgba(255, 255, 255, 0.03); }
.rail-row.is-done .rail-link { color: var(--text-muted); font-weight: 400; }
.rail-row.is-current .rail-link { font-weight: 600; }

/* ============================================================
   Dashboard
   ============================================================ */
.dash-top { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: var(--s-5); align-items: stretch; }
.dash-top > section:first-child { display:flex; flex-direction:column; align-items:flex-start; min-height:17rem; padding:clamp(1.5rem,3vw,2.75rem); border:1px solid var(--line-strong); border-radius:var(--r-lg); background:linear-gradient(105deg,rgba(88,166,255,.09),transparent 65%),var(--surface); }
.dash-top > section:first-child .next-actions { margin-top:auto; padding-top:var(--s-6); }
.course-rail { padding:var(--s-5); border:1px solid var(--line); border-radius:var(--r-lg); background:var(--surface); }
.course-rail .rail-row { padding-top:.375rem; padding-bottom:.375rem; }
.course-rail .rail-more { margin-left:1.5rem; }
.next-title { font-size: var(--fs-32); font-weight: 600; line-height: 1.2; letter-spacing: -0.01em; margin: 0 0 var(--s-2); max-width: 24ch; }
.next-meta { color: var(--text-muted); font-size: var(--fs-16); margin-bottom: var(--s-6); }
.next-actions { display: flex; flex-wrap: wrap; align-items: center; gap: var(--s-2) var(--s-3); }
.next-actions .text-btn { margin-left: calc(-1 * var(--s-2)); }
.next-actions .stitch-btn + .text-btn { margin-left: 0; }

.section-title { font-size: var(--fs-16); font-weight: 600; margin: 0; }
.section-note { color: var(--text-muted); font-size: var(--fs-13); margin: 0.125rem 0 var(--s-3); }
.rail-more { display: inline-flex; margin: var(--s-2) 0 0 var(--s-2); }
.course-rail .rail-link { font-size: var(--fs-14); }

.dash-bottom {
  display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr); gap: var(--s-8) 4rem;
  margin-top: var(--s-6); padding-top: var(--s-6); border-top: 1px solid var(--line);
}
.dash-bottom > section { min-width:0; padding:var(--s-5); border:1px solid var(--line); border-radius:var(--r-lg); background:var(--surface); }
.progress-summary { color: var(--text-muted); font-size: var(--fs-14); margin: 0.25rem 0 var(--s-4); }
.subject-list { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: var(--s-3); }
.subject-row { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: baseline; gap: 0.375rem var(--s-3); }
.subject-name { color: var(--text); font-weight: 500; }
.subject-count { color: var(--text-muted); font-size: var(--fs-13); font-variant-numeric: tabular-nums; }
.subject-row .progress-bar { grid-column: 1 / -1; }

.tool-list { list-style: none; margin: var(--s-3) 0 0; padding: 0; }
.tool-link { display: block; padding: 0.625rem 0; border-top: 1px solid var(--line); color: inherit; }
.tool-list li:last-child .tool-link { border-bottom: 1px solid var(--line); }
.tool-link:hover { text-decoration: none; }
.tool-link:hover .tool-name { text-decoration: underline; }
.tool-name { display: block; color: var(--accent-ink); font-weight: 600; font-size: var(--fs-14); }
.tool-desc { display: block; color: var(--text-muted); font-size: var(--fs-13); }

/* ============================================================
   Topic explorer
   ============================================================ */
.topics-tools { display: flex; flex-wrap: wrap; align-items: center; gap: var(--s-3) var(--s-5); margin-bottom: var(--s-2); }
.topic-search { position: relative; flex: 1 1 16rem; max-width: 24rem; }
.topic-search .material-symbols-outlined { position: absolute; left: 0.625rem; top: 50%; transform: translateY(-50%); font-size: 1.125rem; color: var(--text-faint); pointer-events: none; }
.topic-search .input { padding-left: 2.25rem; }

.topic-status { color: var(--text-muted); font-size: var(--fs-13); margin: var(--s-3) 0 var(--s-4); min-height: 1.25rem; }
.topic-group { margin-top: var(--s-5); padding:var(--s-4); border:1px solid var(--line); border-radius:var(--r-md); background:var(--surface); }
.topic-group-head { display: flex; align-items: baseline; gap: var(--s-3); margin-bottom: var(--s-2); padding-bottom:var(--s-2); border-bottom:1px solid var(--line); }
.topic-group-head h3 { font-size: var(--fs-20); }
.topic-group-count { color: var(--text-muted); font-size: var(--fs-13); font-variant-numeric: tabular-nums; }
.topic-row { display: grid; grid-template-columns: minmax(0, 1fr) auto; column-gap: var(--s-4); align-items: center; min-height:3.5rem; border-bottom:1px solid var(--line); }
.topic-row:last-child { border-bottom:0; }
.topic-main { min-width: 0; }
.topic-link { font-size: var(--fs-14); }
.topic-desc { color: var(--text-muted); font-size: var(--fs-13); line-height: 1.25rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.topic-meta { position: relative; z-index: 1; display: flex; align-items: center; gap: 2px; }
.topic-score { color: var(--text-muted); font-size: var(--fs-13); font-variant-numeric: tabular-nums; margin-right: var(--s-2); }
.topic-empty { margin-top: var(--s-8); padding: var(--s-8) 0; border-top: 1px solid var(--line); }
.topic-empty .stitch-btn { margin-top: var(--s-4); }

/* ============================================================
   Lesson: a reading environment
   ============================================================ */
.lesson { font-size: var(--fs-16); line-height: 1.65; }
.lesson-prose { max-width: 70ch; }
.back-link {
  display: inline-flex; align-items: center; gap: 0.25rem;
  min-height: 2rem; margin-left: calc(-1 * var(--s-1)); padding: 0 var(--s-1);
  color: var(--text-muted); font-size: var(--fs-13);
}
.back-link .material-symbols-outlined { font-size: 1.0625rem; }
.back-link:hover { color: var(--text); text-decoration: none; }
.lesson-head { margin-bottom: var(--s-8); }
.lesson-head .screen-title { margin-top: var(--s-3); }
.lesson-meta { display: flex; flex-wrap: wrap; align-items: center; gap: var(--s-1) var(--s-3); margin-top: var(--s-2); color: var(--text-muted); font-size: var(--fs-14); }
.status-done { display: inline-flex; align-items: center; gap: 0.25rem; color: var(--success-ink); font-weight: 500; }
.status-done .material-symbols-outlined { font-size: 1.125rem; }

.lesson-sec { margin-top: var(--s-8); }
.lesson-sec h3 { font-size: var(--fs-20); margin-bottom: var(--s-3); }
.lesson-sec p { color: var(--text); }
.prose-list { margin: 0; padding-left: 1.25rem; }
.prose-list li { margin-bottom: 0.5rem; padding-left: 0.25rem; }
.prose-list li::marker { color: var(--text-faint); }
.lesson code:not(pre code) {
  font-size: 0.875em; padding: 0.0625rem 0.3125rem;
  background: var(--surface-3); border-radius: 0.25rem; color: var(--text);
  overflow-wrap: anywhere;
}

.callout {
  border-left: 3px solid var(--accent);
  background: rgba(88, 166, 255, 0.06);
  padding: var(--s-3) var(--s-4);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
  color: var(--text); line-height: 1.65;
}
.callout.tip { border-left-color: var(--success); background: rgba(63, 185, 80, 0.07); }
.callout strong { display: block; color: var(--success-ink); font-size: var(--fs-13); font-weight: 600; margin-bottom: 2px; }
.lesson .callout { margin-top: var(--s-8); }

/* Code blocks */
.code-panel {
  max-width: 85ch;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  overflow: hidden;
  background: #0b0f14;
}
.code-panel-bar {
  display: flex; justify-content: space-between; gap: var(--s-3);
  padding: 0.5rem var(--s-4);
  background: var(--surface-2);
  border-bottom: 1px solid var(--line);
  font-size: var(--fs-12); color: var(--text-muted);
  font-family: var(--font-mono);
}
.code-scroll { overflow-x: auto; }
.code-scroll:focus-visible { outline-offset: -2px; border-radius: 0; }
.code-panel pre {
  margin: 0; padding: var(--s-4);
  width: max-content; min-width: 100%;
  font-size: var(--fs-13); line-height: 1.65;
  color: #c9d1d9;
  white-space: pre;
  tab-size: 4;
}
.code-panel pre code { color: inherit; }

.lesson-end { margin-top: 3rem; padding-top: var(--s-6); border-top: 1px solid var(--line); }
.lesson-end .muted { margin-top: var(--s-3); }
.lesson-end h3 { font-size: var(--fs-20); margin-bottom: var(--s-4); }
.lesson-pager { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s-4); margin-top: var(--s-8); }
.pager-link { display: block; padding: var(--s-2) 0; min-height: var(--touch); color: var(--text); min-width: 0; }
.pager-link:hover { text-decoration: none; }
.pager-link:hover .pager-title { text-decoration: underline; }
.pager-link.next { grid-column: 2; text-align: right; }
.pager-label { display: block; color: var(--text-muted); font-size: var(--fs-13); }
.pager-title { display: block; color: var(--accent-ink); font-weight: 600; overflow-wrap: anywhere; }

/* Tokens (GitHub dark) */
.tok-kw { color: #ff7b72; }
.tok-str { color: #a5d6ff; }
.tok-com { color: #8b949e; font-style: italic; }
.tok-num { color: #79c0ff; }
.tok-fn { color: #d2a8ff; }
.tok-pre { color: #ff7b72; }
.tok-tag { color: #7ee787; }
.tok-attr { color: #d2a8ff; }
.tok-prop { color: #79c0ff; }
:root[data-theme="light"] .tok-kw, :root[data-theme="light"] .tok-pre { color: #cf222e; }
:root[data-theme="light"] .tok-str { color: #0550ae; }
:root[data-theme="light"] .tok-com { color: #6e7781; }
:root[data-theme="light"] .tok-num, :root[data-theme="light"] .tok-prop { color: #0969da; }
:root[data-theme="light"] .tok-fn, :root[data-theme="light"] .tok-attr { color: #8250df; }
:root[data-theme="light"] .tok-tag { color: #116329; }
:root[data-theme="light"] .xp-chip { color:var(--success-ink); background:rgba(26,127,55,.08); border-color:rgba(26,127,55,.22); }
:root[data-theme="light"] .progress-hero { background:linear-gradient(110deg,rgba(9,105,218,.07),transparent 58%),var(--surface); }

/* ============================================================
   Quiz
   ============================================================ */
.quiz-back { margin-left: calc(-1 * var(--s-2)); }
.quiz-back .material-symbols-outlined { font-size: 1.0625rem; }
.quiz-head, .quiz-body, .result-card, .quiz-review { max-width: 48rem; }
.quiz-head { margin-bottom: var(--s-6); }
.quiz-head .screen-title { margin-top: var(--s-2); }
.quiz-count { color: var(--text-muted); font-size: var(--fs-14); margin: var(--s-2) 0 var(--s-4); }

/* One segment per question, coloured by the real result so far. */
.quiz-segs { display: flex; gap: 0.25rem; list-style: none; margin: 0; padding: 0; }
.seg { flex: 1 1 0; height: 0.375rem; border-radius: 2px; background: var(--surface-4); }
.seg.correct { background: var(--success); }
.seg.wrong { background: var(--danger); }
.seg.current { background: var(--accent); }

.quiz-question { font-size: var(--fs-20); font-weight: 600; line-height: 1.45; margin: 0 0 var(--s-5); }
.quiz-body { padding:clamp(1rem,2.5vw,1.75rem); border:1px solid var(--line); border-radius:var(--r-md); background:var(--surface); }
.quiz-options { display: flex; flex-direction: column; gap: var(--s-2); }
.quiz-option {
  display: flex; align-items: center; gap: var(--s-3);
  width: 100%; min-height: 3rem;
  padding: 0.625rem var(--s-4);
  border: 1px solid var(--line-strong); border-radius: var(--r-sm);
  background: var(--surface-2);
  color: var(--text); font-size: var(--fs-14); text-align: left;
  cursor: pointer;
  transition: border-color var(--ease), background var(--ease);
}
.quiz-option:hover:not(:disabled) { border-color: var(--accent); background: var(--surface-3); }
.quiz-option .key {
  display: grid; place-items: center;
  width: 1.5rem; height: 1.5rem; flex: 0 0 1.5rem;
  border-radius: var(--r-sm); border: 1px solid var(--line-strong);
  font-family: var(--font-mono); font-size: var(--fs-12); color: var(--text-muted);
}
.quiz-option .label { flex: 1 1 auto; min-width: 0; overflow-wrap: anywhere; }
.quiz-option .state { display: inline-flex; align-items: center; gap: 0.25rem; font-size: var(--fs-12); font-weight: 600; white-space: nowrap; }
.quiz-option .state .material-symbols-outlined { font-size: 1.125rem; }
.quiz-option.selected { border-color: var(--accent); background: rgba(88, 166, 255, 0.1); }
.quiz-option.selected .key { border-color: var(--accent); color: var(--accent-ink); }
.quiz-option.selected .state { color: var(--accent-ink); }
.quiz-option.correct { border-color: var(--success); background: rgba(63, 185, 80, 0.1); }
.quiz-option.correct .state, .quiz-option.correct .key { color: var(--success-ink); }
.quiz-option.wrong { border-color: var(--danger); background: rgba(248, 81, 73, 0.1); }
.quiz-option.wrong .state, .quiz-option.wrong .key { color: var(--danger-ink); }
.quiz-option:disabled { cursor: default; opacity: 1; color: var(--text); }

.feedback {
  margin-top: var(--s-4); padding: var(--s-3) var(--s-4);
  border-left: 3px solid var(--line-strong); border-radius: 0 var(--r-sm) var(--r-sm) 0;
  background: rgba(255, 255, 255, 0.03);
  font-size: var(--fs-14); line-height: 1.6; color: var(--text);
}
.feedback strong { display: flex; align-items: center; gap: 0.375rem; margin-bottom: 0.25rem; font-weight: 600; }
.feedback strong .material-symbols-outlined { font-size: 1.125rem; }
.feedback.ok { border-left-color: var(--success); background: rgba(63, 185, 80, 0.07); }
.feedback.ok strong { color: var(--success-ink); }
.feedback.bad { border-left-color: var(--danger); background: rgba(248, 81, 73, 0.07); }
.feedback.bad strong { color: var(--danger-ink); }
.quiz-actions { margin-top: var(--s-5); }

.result-topic { color: var(--text-muted); margin-top: var(--s-2); }
.result-card .screen-title { margin-top: var(--s-1); }
.result-score { font-size: 3rem; font-weight: 700; line-height: 1.1; letter-spacing: -0.02em; font-variant-numeric: tabular-nums; margin: var(--s-2) 0 var(--s-4); }
.result-card .quiz-segs { max-width: 20rem; }
.result-line { color: var(--text-muted); margin-top: var(--s-3); }
.result-xp { display: flex; align-items: center; gap: 0.375rem; margin-top: var(--s-1); color: var(--text); font-weight: 500; }
.result-xp .material-symbols-outlined { font-size: 1.125rem; color: var(--accent); }
.result-actions { margin-top: var(--s-6); }
.quiz-review { margin-top: 3rem; padding-top: var(--s-6); border-top: 1px solid var(--line); }
.review-list { list-style: none; margin: var(--s-4) 0 0; padding: 0; display: flex; flex-direction: column; gap: var(--s-6); }
.review-q { font-weight: 600; font-size: var(--fs-16); line-height: 1.45; margin-bottom: var(--s-2); }
.review-line { display: flex; align-items: flex-start; gap: 0.5rem; margin-top: 0.25rem; }
.review-line .material-symbols-outlined { font-size: 1.125rem; margin-top: 0.125rem; }
.review-line.wrong .material-symbols-outlined { color: var(--danger-ink); }
.review-line.correct .material-symbols-outlined { color: var(--success-ink); }
.review-tag { color: var(--text-muted); }
.review-why { margin-top: var(--s-2); padding-left: 1.625rem; color: var(--text-muted); }

/* ============================================================
   Output prediction
   ============================================================ */
.predict-filters { margin-bottom: var(--s-6); }
.predict-layout { display: grid; grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr); gap: var(--s-8); align-items: start; }
.predict-code .code-panel { max-width: none; }
.predict-code .code-panel pre { font-size: var(--fs-14); }
.mono-input { font-family: var(--font-mono); }
.predict-actions { margin-top: var(--s-3); }
.predict-next { margin-top: var(--s-6); padding-top: var(--s-4); border-top: 1px solid var(--line); }
.compare { display: grid; grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr)); gap: var(--s-3); margin: var(--s-3) 0; }
.compare-label { display: block; font-size: var(--fs-12); font-weight: 500; color: var(--text-muted); margin-bottom: 0.25rem; }
.compare-out {
  margin: 0; padding: 0.5rem 0.625rem; min-height: 2.25rem;
  background: #0b0f14; border: 1px solid var(--line); border-radius: var(--r-sm);
  font-size: var(--fs-13); color: var(--text); white-space: pre-wrap; overflow-wrap: anywhere;
}
.compare-none { display: block; padding: 0.5rem 0; color: var(--text-muted); font-style: italic; }
.compare-why { margin: var(--s-2) 0 0; }
.compare-xp { margin: var(--s-2) 0 0; color: var(--text-muted); font-size: var(--fs-13); }
.inline-strong { display: inline; margin: 0; font-weight: 600; }

/* ============================================================
   Visualization workspace
   One toolbar, code on the left with its transport attached below,
   the current state on the right.
   ============================================================ */
.viz-heading { margin-bottom: var(--s-4); }
.viz-toolbar {
  display: flex; align-items: center; justify-content: space-between; gap: var(--s-3) var(--s-4);
  flex-wrap: wrap; margin-bottom: var(--s-4);
}
.viz-tabs { display: inline-flex; max-width: 100%; overflow-x: auto; gap: 2px; padding: 0.1875rem; border-radius: var(--r-md); background: var(--surface); border: 1px solid var(--line); }
.viz-tab {
  min-height: 2rem; padding: 0.3125rem 0.75rem;
  border: 0; border-radius: var(--r-sm);
  background: transparent; color: var(--text-muted);
  font-size: var(--fs-13); font-weight: 600; cursor: pointer; white-space: nowrap;
}
.viz-tab:hover { color: var(--text); background: rgba(255, 255, 255, 0.05); }
.viz-tab.active { background: var(--surface-3); color: var(--text); }
.viz-topic { display: flex; align-items: center; gap: var(--s-2); }
.viz-topic .field-label { margin: 0; }
.viz-topic .select { width: auto; min-width: 12.5rem; max-width: 20rem; }
.viz-fixed { color: var(--text-muted); font-size: var(--fs-13); }

.viz-workspace { display: grid; grid-template-columns: minmax(0, 1.2fr) minmax(0, 1fr); gap: var(--s-6); align-items: start; }
.viz-left, .viz-right { min-width: 0; }
.viz-left { display: flex; flex-direction: column; }
.viz-right { display: flex; flex-direction: column; gap: var(--s-5); }

.viz-codewrap { border: 1px solid var(--line); border-radius: var(--r-md); overflow: hidden; background: #0b0f14; }
.has-transport .viz-codewrap { border-bottom-left-radius: 0; border-bottom-right-radius: 0; }
.viz-code-bar {
  display: flex; align-items: center; justify-content: space-between; gap: var(--s-3);
  padding: 0.4375rem var(--s-4);
  background: var(--surface-2); border-bottom: 1px solid var(--line);
  font-family: var(--font-mono); font-size: var(--fs-12); color: var(--text-muted);
}
.viz-code {
  max-height: min(30rem, 62vh); overflow: auto; padding: 0.5rem 0;
  font-family: var(--font-mono); font-size: var(--fs-13); line-height: 1.7;
}
.viz-code:focus-visible { outline-offset: -2px; border-radius: 0; }
.viz-line { display: flex; width: max-content; min-width: 100%; }
.viz-line .pc { flex: 0 0 1.25rem; display: grid; place-items: center; }
.viz-line .ln { flex: 0 0 2rem; text-align: right; padding-right: 0.75rem; color: var(--text-faint); user-select: none; font-size: var(--fs-12); }
.viz-line .code { flex: 1 1 auto; padding-right: var(--s-4); white-space: pre; }
.viz-line.active { background: rgba(88, 166, 255, 0.12); }
.viz-line.active .ln { color: var(--accent-ink); }

/* The program counter, reused: gutter arrow for the current line and the running stack frame. */
.pc::before { content: ""; display: block; width: 0.625rem; height: 0.75rem; clip-path: polygon(0 0, 100% 50%, 0 100%); }
.viz-line.active .pc::before, .frame.current .pc::before { background: var(--accent); }
@media (forced-colors: active) {
  .viz-line.active { outline: 2px solid Highlight; outline-offset: -2px; }
  .viz-line.active .pc::before, .frame.current .pc::before { forced-color-adjust: none; background: Highlight; }
}

.viz-transport {
  display: flex; align-items: center; justify-content: space-between; gap: var(--s-3) var(--s-4); flex-wrap: wrap;
  padding: var(--s-3) var(--s-4);
  background: var(--surface-2); border: 1px solid var(--line); border-top: 0;
  border-radius: 0 0 var(--r-md) var(--r-md);
}
.transport-progress { flex: 1 1 8rem; min-width: 7rem; display: flex; flex-direction: column; gap: 0.375rem; }
.viz-step-label { font-family: var(--font-mono); font-size: var(--fs-12); color: var(--text-muted); font-variant-numeric: tabular-nums; }
.transport-buttons { display: flex; gap: var(--s-2); }
.transport-buttons .stitch-btn { min-height: 2.25rem; padding: 0.375rem 0.75rem; }
.transport-buttons .stitch-btn .material-symbols-outlined { font-size: 1.125rem; }
.viz-note { color: var(--text-muted); font-size: var(--fs-13); margin-top: var(--s-3); }

.viz-source { display: flex; flex-direction: column; gap: 0.125rem; }
.viz-source-label { display: inline-flex; align-items: center; gap: 0.375rem; font-size: var(--fs-13); font-weight: 600; color: var(--accent-ink); }
.viz-source-label .material-symbols-outlined { font-size: 1.125rem; }
.viz-source-note { color: var(--text-muted); font-size: var(--fs-13); }
.viz-section h3 { font-size: var(--fs-13); font-weight: 600; color: var(--text-muted); margin-bottom: var(--s-2); }
.viz-step-text { font-size: var(--fs-16); line-height: 1.5; min-height: 3em; }

.viz-table { width: 100%; border-collapse: collapse; font-family: var(--font-mono); font-size: var(--fs-13); }
.viz-table th { text-align: left; padding: 0.375rem 0.625rem; font-size: var(--fs-12); font-weight: 600; color: var(--text-muted); border-bottom: 1px solid var(--line); }
.viz-table td, .viz-table th[scope="row"] { padding: 0.375rem 0.625rem; border-bottom: 1px solid var(--line); color: var(--text); }
.viz-table th[scope="row"] { color: var(--accent-ink); font-weight: 600; width: 6rem; font-size: var(--fs-13); }
.viz-table tr:last-child td, .viz-table tr:last-child th[scope="row"] { border-bottom: 0; }
.viz-table tr.active td { background: rgba(88, 166, 255, 0.1); }
.table-scroll { overflow: auto; max-height: 16rem; }

.terminal { border: 1px solid var(--line); border-radius: var(--r-md); overflow: hidden; background: #0b0f14; }
.terminal-bar { display: flex; align-items: center; gap: 0.375rem; padding: 0.3125rem var(--s-3); background: var(--surface-2); border-bottom: 1px solid var(--line); font-size: var(--fs-12); color: var(--text-muted); }
.terminal-bar .material-symbols-outlined { font-size: 1rem; }
.console {
  margin: 0; padding: var(--s-3); min-height: 3.5rem; max-height: 12rem; overflow: auto;
  font-family: var(--font-mono); font-size: var(--fs-13); line-height: 1.6;
  color: var(--success-ink); white-space: pre-wrap; overflow-wrap: anywhere;
}

/* Flow: statements in source order, joined by short connectors */
.flow-chart { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; max-width: 28rem; }
.flow-node {
  position: relative; margin-bottom: 1.25rem; padding: 0.5rem 0.75rem;
  border: 1px solid var(--line-strong); border-radius: var(--r-sm);
  background: #0b0f14; font-family: var(--font-mono); font-size: var(--fs-13); overflow-wrap: anywhere;
}
.flow-node:last-child { margin-bottom: 0; }
.flow-node:not(:last-child)::after { content: ""; position: absolute; left: 50%; top: 100%; height: 1.25rem; width: 1px; background: var(--text-faint); }
.flow-node:not(:last-child)::before {
  content: ""; position: absolute; left: calc(50% - 4px); top: calc(100% + 0.8125rem);
  border-left: 4px solid transparent; border-right: 4px solid transparent; border-top: 5px solid var(--text-faint);
}
.flow-node.decision { border-color: rgba(188, 140, 255, 0.5); border-radius: var(--r-pill); text-align: center; color: #e2d1ff; }
.flow-node.branch { border-color: rgba(210, 153, 34, 0.5); color: #e3b341; }
.flow-node.terminator { border-color: rgba(63, 185, 80, 0.55); text-align: center; color: var(--success-ink); font-weight: 600; }

.viz-unsupported { padding: var(--s-4) var(--s-5); border-left: 3px solid var(--warn); background: rgba(210, 153, 34, 0.06); border-radius: 0 var(--r-md) var(--r-md) 0; }
.viz-unsupported h3 { display: flex; align-items: center; gap: 0.5rem; font-size: var(--fs-16); margin-bottom: var(--s-2); }
.viz-unsupported h3 .material-symbols-outlined { color: #e3b341; }
.viz-unsupported p { color: var(--text-muted); margin-bottom: var(--s-4); }

/* Pointers: a small memory table */
.mem-grid { border: 1px solid var(--line); border-radius: var(--r-md); overflow: hidden; background: #0b0f14; }
.mem-row {
  display: grid; grid-template-columns: 2.5rem 4.5rem minmax(0, 1fr) auto; align-items: center; gap: var(--s-3);
  padding: 0.625rem var(--s-3); border-bottom: 1px solid var(--line);
  font-family: var(--font-mono); font-size: var(--fs-13);
}
.mem-row:last-child { border-bottom: 0; }
.mem-name { font-weight: 600; color: var(--accent-ink); }
.mem-type, .mem-row.is-empty .mem-value { color: var(--text-muted); }
.mem-row.is-empty .mem-value { font-style: italic; }
.mem-points { display: inline-flex; align-items: center; gap: 0.25rem; color: var(--success-ink); font-size: var(--fs-12); }
.mem-points .material-symbols-outlined { font-size: 1.125rem; }

/* Recursion: a real stack, growing up from its floor; the running frame carries the arrow */
.call-stack {
  list-style: none; margin: 0; padding: 0 0 var(--s-2); display: flex; flex-direction: column; justify-content: flex-end; gap: 0.25rem;
  min-height: 14rem; border-bottom: 2px solid var(--line-strong);
}
.frame {
  position: relative; display: flex; flex-direction: column; padding: 0.5rem var(--s-3) 0.5rem 1.75rem;
  border: 1px solid var(--line); border-radius: var(--r-sm); background: #0b0f14;
}
.frame .pc { position: absolute; left: 0.5rem; top: 0.75rem; }
.frame.current { border-color: rgba(88, 166, 255, 0.5); background: rgba(88, 166, 255, 0.08); }
.frame-call { font-family: var(--font-mono); font-size: var(--fs-13); font-weight: 600; }
.frame-state { font-size: var(--fs-12); color: var(--text-muted); }
.frame.is-empty { padding-left: var(--s-3); color: var(--text-muted); border-style: dashed; }

/* ============================================================
   Logic Quest: the program-counter rail at map scale
   ============================================================ */
.quest-standing { color: var(--text); font-weight: 600; }
.quest-layout { display: grid; grid-template-columns: minmax(0, 34rem) minmax(0, 1fr); gap: 4rem; align-items: start; }
.quest-map { --quest-line: #2a313a; display: flex; flex-direction: column; }
.quest-chapter-head, .quest-blurb, .quest-step { position: relative; padding-left: 3rem; }
.quest-chapter-head { display: flex; align-items: baseline; gap: var(--s-3); padding-top: var(--s-1); }
.quest-chapter-head h3 { font-size: var(--fs-20); color: var(--purple); }
.quest-chapter-count { color: var(--text-faint); font-size: var(--fs-13); font-variant-numeric: tabular-nums; }
.quest-blurb { color: var(--text-muted); font-size: var(--fs-13); padding-bottom: var(--s-4); }
/* The rail: one thin line down the left, drawn per block so it runs unbroken through the chapters. */
.quest-chapter-head::before, .quest-blurb::before, .quest-step::before {
  content: ""; position: absolute; left: 1rem; top: 0; bottom: 0; width: 1px; background: var(--quest-line);
}
.quest-chapter:first-child .quest-chapter-head::before { top: 1rem; }
.quest-chapter-head::after { /* chapter marker on the rail */
  content: ""; position: absolute; left: 1rem; top: 1rem; width: 0.625rem; height: 0.625rem;
  background: var(--purple); transform: translate(-50%, -50%) rotate(45deg); border-radius: 2px;
}
.quest-chapter:last-child .quest-step:last-child::before { bottom: auto; height: 2rem; }
.quest-levels { list-style: none; margin: 0; padding: 0; }
.quest-step { padding-bottom: var(--s-3); }
.quest-chapter:not(:last-child) .quest-step:last-child { padding-bottom: var(--s-8); }

.quest-node-mark {
  position: absolute; z-index: 1; left: 1rem; top: 2rem; width: 1.25rem; height: 1.25rem;
  transform: translate(-50%, -50%); border-radius: 50%;
  display: grid; place-items: center;
  background: var(--bg); border: 2px solid var(--text-faint); color: var(--text-faint);
}
.quest-node-mark .material-symbols-outlined { font-size: 0.8125rem; }
.quest-node-mark.done { background: var(--text-muted); border-color: var(--text-muted); color: var(--bg); }
.quest-node-mark.current {
  width: 1.5rem; height: 1.75rem; border: 0; border-radius: 0; background: var(--accent);
  clip-path: polygon(0 0, 100% 50%, 0 100%); transform: translate(-38%, -50%);
}
@media (forced-colors: active) {
  .quest-node-mark.current { forced-color-adjust: none; background: Highlight; }
  .quest-node-mark.done { forced-color-adjust: none; background: CanvasText; }
}

.quest-node {
  display: grid; grid-template-columns: minmax(0, 1fr) auto; grid-template-areas: "name status" "meta status";
  align-items: center; column-gap: var(--s-4);
  width: 100%; min-height: 4rem; padding: 0.625rem var(--s-4);
  border: 1px solid var(--line-strong); border-radius: var(--r-md);
  background: var(--surface); color: var(--text); text-align: left; cursor: pointer;
  transition: border-color var(--ease), background var(--ease);
}
.quest-node:hover:not(:disabled) { border-color: var(--accent); background: var(--surface-2); }
.quest-name { grid-area: name; font-weight: 600; font-size: var(--fs-14); }
.quest-meta { grid-area: meta; color: var(--text-muted); font-size: var(--fs-12); }
.quest-status { grid-area: status; display: inline-flex; align-items: center; gap: 0.375rem; font-size: var(--fs-13); color: var(--text-muted); text-align: right; }
.quest-status .material-symbols-outlined { font-size: 1.0625rem; }
.quest-node.done .quest-status { color: var(--success-ink); }
.quest-node.current { border-color: var(--accent); background: rgba(88, 166, 255, 0.08); min-height: 4.5rem; }
.quest-node.current .quest-name { font-size: var(--fs-16); }
.quest-start-cta { padding: 0.4375rem 1.125rem; border-radius: var(--r-sm); background: var(--accent-solid); color: #fff; font-weight: 600; font-size: var(--fs-14); }
.quest-node.current:hover .quest-start-cta { background: var(--accent-solid-hover); }
.quest-node:disabled { cursor: default; background: transparent; border-style: dashed; color: var(--text-muted); }
.quest-node:disabled .quest-name { color: var(--text); }

.quest-aside { position: sticky; top: var(--s-4); max-width: 24rem; padding-left: var(--s-6); border-left: 1px solid var(--line); color: var(--text-muted); font-size: var(--fs-14); }
.quest-aside p { margin-top: var(--s-3); }
.quest-aside strong { color: var(--text); }

.quest-play-head, .quest-challenge-panel { max-width: 62rem; }
.quest-play-head { margin-bottom: var(--s-5); }
.quest-kicker { color: var(--purple); font-size: var(--fs-13); font-weight: 600; margin-top: var(--s-2); }
.quest-play-head .screen-title { margin-top: var(--s-1); }
.quest-challenge { display: flex; align-items: center; flex-wrap: wrap; gap: var(--s-2) var(--s-3); margin-top: var(--s-3); color: var(--text-muted); font-size: var(--fs-14); }
.quest-goal { font-size: var(--fs-16); margin-bottom: var(--s-4); }
.quest-challenge-panel { padding: clamp(1rem, 2.4vw, 2rem); border: 1px solid var(--line); border-radius: var(--r-md); background: var(--surface); }
.quest-challenge-panel .code-panel { margin-bottom: var(--s-5); }
.quest-tools { margin-top: var(--s-4); }
.exec-state { display: flex; flex-wrap: wrap; gap: var(--s-2) var(--s-8); margin: 0 0 var(--s-5); }
.exec-state dt { color: var(--text-muted); font-size: var(--fs-12); }
.exec-state dd { margin: 0; font-family: var(--font-mono); font-size: var(--fs-20); font-weight: 600; }
.action-grid { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s-2); }
.action-btn {
  min-height: 3rem; padding: 0.5625rem var(--s-4);
  border: 1px solid var(--line-strong); border-radius: var(--r-sm);
  background: var(--surface-2); color: var(--text);
  font-size: var(--fs-14); text-align: left; cursor: pointer;
  transition: border-color var(--ease), background var(--ease);
}
.action-btn:hover:not(:disabled) { border-color: var(--accent); background: var(--surface-3); }
.action-btn:disabled { cursor: default; color: var(--text-muted); }
.exec-log-title { margin: var(--s-6) 0 var(--s-2); font-size: var(--fs-14); color: var(--text-muted); }

/* ============================================================
   Analyzer
   ============================================================ */
.notice {
  display: flex; align-items: flex-start; gap: var(--s-3);
  max-width: 60rem; margin-bottom: var(--s-6); padding: var(--s-3) var(--s-4);
  border-left: 3px solid var(--warn); border-radius: 0 var(--r-sm) var(--r-sm) 0;
  background: rgba(210, 153, 34, 0.07); color: var(--text); font-size: var(--fs-14);
}
.notice .material-symbols-outlined { color: #e3b341; font-size: 1.25rem; }
.analyzer-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: var(--s-8); align-items: start; }
.analyzer-pane { min-width: 0; }
.pane-head { display: flex; align-items: center; justify-content: space-between; gap: var(--s-3); min-height: 2.5rem; margin-bottom: var(--s-3); }
.pane-title { font-size: var(--fs-16); }
.field-inline { display: flex; align-items: center; gap: var(--s-2); }
.field-inline .field-label { margin: 0; }
.field-inline .select { width: auto; min-width: 9rem; }
.analyzer-pane .code-textarea { min-height: 22rem; }
.pane-foot { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: var(--s-2) var(--s-4); margin-top: var(--s-3); }
.pane-foot .button-row { gap: var(--s-3); }
.is-near-limit { color: #e3b341; }
.analyzer-empty { padding: var(--s-5) 0; }
.analyzer-empty-title { font-weight: 600; font-size: var(--fs-16); margin-bottom: var(--s-1); }
.analyzer-empty .button-row { margin-top: var(--s-4); }
.analysis-summary { display: flex; align-items: baseline; gap: 0.5rem; margin-bottom: var(--s-3); color: var(--text-muted); }
.analysis-count { font-size: var(--fs-20); font-weight: 600; color: var(--text); }
.atree {
  list-style: none; margin: 0; padding: var(--s-2) var(--s-3); max-height: 30rem; overflow: auto;
  border: 1px solid var(--line); border-radius: var(--r-md); background: #0b0f14;
}
.atree-node { display: flex; align-items: center; flex-wrap: wrap; gap: 0.25rem 0.625rem; padding: 0.3125rem 0 0.3125rem calc(var(--d, 0) * 1.25rem); }
.atree-icon { font-size: 1.0625rem; color: var(--text-faint); }
.atree-label { font-family: var(--font-mono); font-size: var(--fs-13); color: var(--text); overflow-wrap: anywhere; }
.atree-kind { font-size: var(--fs-12); color: var(--accent-ink); }
.atree-detail { font-size: var(--fs-12); color: var(--text-muted); overflow-wrap: anywhere; }

/* ============================================================
   Study assistant
   ============================================================ */
.chat-shell { display: flex; flex-direction: column; height: 100%; min-height: 0; width: 100%; max-width: 46rem; margin: 0 auto; }
.chat-head { padding: var(--s-5) var(--s-5) var(--s-4); border-bottom: 1px solid var(--line); }
.chat-title { font-size: var(--fs-20); }
.chat-sub { margin-top: 0.25rem; color: var(--text-muted); font-size: var(--fs-13); }
.chat-sub strong { color: var(--text); }
.chat-log { flex: 1 1 auto; min-height: 0; overflow-y: auto; padding: var(--s-5); display: flex; flex-direction: column; gap: var(--s-3); }
.chat-bubble { max-width: 85%; padding: 0.625rem 0.875rem; border-radius: var(--r-md); font-size: var(--fs-14); line-height: 1.6; white-space: pre-wrap; overflow-wrap: anywhere; }
.chat-bubble.user { align-self: flex-end; background: var(--accent-solid); color: #fff; border-bottom-right-radius: 0.25rem; }
.chat-bubble.bot { align-self: flex-start; background: var(--surface-2); border: 1px solid var(--line); border-bottom-left-radius: 0.25rem; }
.chat-bubble code { font-size: 0.875em; padding: 0.0625rem 0.3125rem; background: rgba(255, 255, 255, 0.08); border-radius: 0.25rem; }
.suggestions { display: flex; flex-wrap: wrap; gap: var(--s-2); padding: 0 var(--s-5) var(--s-3); }
.suggest-chip {
  min-height: 2.25rem; padding: 0.3125rem 0.75rem;
  border: 1px solid var(--line-strong); border-radius: var(--r-pill);
  background: transparent; color: var(--text-muted); font-size: var(--fs-13); cursor: pointer;
}
.suggest-chip:hover { border-color: var(--accent); color: var(--accent-ink); }
.chat-composer { display: flex; align-items: flex-start; gap: var(--s-2); padding: var(--s-3) var(--s-5) var(--s-4); border-top: 1px solid var(--line); }
.chat-field { position: relative; flex: 1 1 auto; min-width: 0; }
.chat-field .input { padding-right: 4.5rem; }
.chat-count { position: absolute; right: 0.75rem; top: 50%; transform: translateY(-50%); pointer-events: none; font-variant-numeric: tabular-nums; }
.chat-send { width: 2.5rem; padding: 0; flex: 0 0 2.5rem; }

/* ============================================================
   Practice and progress
   ============================================================ */
.quiet-empty { max-width: 58rem; padding:clamp(1.25rem,3vw,2rem); border:1px solid var(--line); border-radius:var(--r-md); background:var(--surface); }
.practice-next { margin-bottom: var(--s-8); }
.progress-sec { margin-top: var(--s-8); max-width: 64rem; }
.progress-sec .subject-list { margin-top: var(--s-3); }
.plain-list { list-style: none; margin: var(--s-3) 0 0; padding: 0; }
.plain-row { display: flex; align-items: center; justify-content: space-between; gap: var(--s-3); min-height: var(--touch); padding: 0.375rem 0; border-top: 1px solid var(--line); }
.plain-row:last-child { border-bottom: 1px solid var(--line); }
.plain-main { display: flex; flex-direction: column; min-width: 0; }
.plain-link { color: var(--text); font-weight: 500; }
.plain-meta { color: var(--text-muted); font-size: var(--fs-13); }
.stat-strip { display: flex; flex-wrap: wrap; gap: var(--s-3) var(--s-10); margin: 0 0 var(--s-6); padding: var(--s-4) 0; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.stat { display: flex; flex-direction: column-reverse; }
.progress-page-head { display:flex; align-items:flex-end; justify-content:space-between; gap:var(--s-5); margin-bottom:var(--s-6); }
.progress-page-head .eyebrow, .progress-hero .eyebrow, .section-heading-row .eyebrow, .progress-card .eyebrow { display:block; text-transform:uppercase; letter-spacing:.1em; font-size:var(--fs-12); font-weight:650; }
.privacy-note { display:flex; align-items:center; gap:var(--s-2); color:var(--text-muted); font-size:var(--fs-13); white-space:nowrap; padding-bottom:.25rem; }
.privacy-note .material-symbols-outlined { font-size:1rem; }
.progress-hero { display:grid; grid-template-columns:minmax(0,1fr) auto; align-items:center; gap:var(--s-8); padding:clamp(1.5rem,3.5vw,3rem); border:1px solid var(--line-strong); border-radius:var(--r-lg); background:linear-gradient(110deg, rgba(88,166,255,.09), transparent 58%), var(--surface); }
.progress-hero-copy { max-width:58ch; }
.progress-hero-copy h3 { font-size:clamp(1.5rem,2.5vw,2rem); letter-spacing:-.025em; margin:.2rem 0 var(--s-2); }
.progress-hero-copy p { color:var(--text-muted); max-width:58ch; }
.progress-hero-actions { display:flex; align-items:center; flex-wrap:wrap; gap:var(--s-2) var(--s-4); margin-top:var(--s-5); }
.progress-overall { display:grid; justify-items:center; gap:var(--s-2); min-width:10rem; text-align:center; }
.progress-ring { --progress:0%; width:8.5rem; aspect-ratio:1; display:grid; place-items:center; border-radius:50%; background:radial-gradient(closest-side,var(--surface) 82%,transparent 84% 100%), conic-gradient(var(--accent) var(--progress),var(--surface-3) 0); }
.progress-ring div { display:grid; gap:.1rem; }
.progress-ring strong { font-size:1.8rem; line-height:1.1; font-variant-numeric:tabular-nums; }
.progress-ring span, .progress-overall p span { color:var(--text-muted); font-size:var(--fs-12); }
.progress-overall p { display:grid; }
.progress-overall p strong { font-size:var(--fs-14); font-variant-numeric:tabular-nums; }
.progress-stats { display:grid; grid-template-columns:repeat(4,minmax(0,1fr)); gap:0; margin:var(--s-5) 0 var(--s-8); padding:var(--s-4) 0; }
.progress-stat { min-width:0; padding:0 var(--s-5); border-right:1px solid var(--line); }
.progress-stat:first-child { padding-left:0; }
.progress-stat:last-child { border:0; }
.progress-stat { flex-direction:column; }
.progress-stat .stat-label { display:flex; align-items:center; gap:var(--s-2); order:0; font-size:var(--fs-13); }
.stat-icon { display:inline-grid; place-items:center; width:1.5rem; height:1.5rem; color:var(--accent-ink); background:rgba(88,166,255,.1); border-radius:var(--r-sm); }
.stat-icon .material-symbols-outlined { font-size:1rem; }
.progress-stat .stat-value { order:1; font-size:1.65rem; margin:.15rem 0 .25rem; }
.progress-stat .stat-note { order:2; color:var(--text-faint); font-size:var(--fs-12); }
.section-heading-row { display:flex; justify-content:space-between; align-items:end; gap:var(--s-4); margin-bottom:var(--s-3); }
.section-heading-row .section-title { font-size:var(--fs-20); }
.course-progress-grid { list-style:none; display:grid; grid-template-columns:repeat(4,minmax(0,1fr)); gap:var(--s-3); padding:0; margin:0; }
.course-progress-link { min-width:0; min-height:11.5rem; display:grid; grid-template-columns:auto 1fr auto; align-content:start; align-items:center; gap:var(--s-3) var(--s-2); padding:var(--s-4); border:1px solid var(--line); border-radius:var(--r-md); background:var(--surface); color:inherit; transition:border-color var(--ease),background var(--ease),transform var(--ease); }
.course-progress-link:hover { text-decoration:none; border-color:rgba(88,166,255,.42); background:var(--surface-2); transform:translateY(-1px); }
.course-mark { display:grid; place-items:center; width:2.25rem; height:2.25rem; color:var(--accent-ink); background:rgba(88,166,255,.1); border-radius:var(--r-sm); }
.course-mark .material-symbols-outlined { font-size:1.15rem; }
.course-card-copy { display:grid; min-width:0; gap:.15rem; }
.course-card-copy strong { font-size:var(--fs-14); }
.course-card-copy span, .course-next { color:var(--text-muted); font-size:var(--fs-12); }
.course-percent { color:var(--accent-ink); font-weight:650; font-variant-numeric:tabular-nums; }
.course-track { grid-column:1/-1; height:.375rem; overflow:hidden; border-radius:var(--r-pill); background:var(--surface-3); margin-top:var(--s-2); }
.course-track span { display:block; height:100%; background:var(--accent); border-radius:inherit; }
.course-next { grid-column:1/-1; overflow:hidden; white-space:nowrap; text-overflow:ellipsis; }
.progress-detail-grid { display:grid; grid-template-columns:minmax(0,1.35fr) minmax(17rem,.8fr); gap:var(--s-4); margin-top:var(--s-8); align-items:start; }
.progress-card { min-width:0; padding:var(--s-5); border:1px solid var(--line); border-radius:var(--r-md); background:var(--surface); }
.progress-card-heading { display:flex; align-items:center; justify-content:space-between; gap:var(--s-3); }
.progress-card-heading h3 { margin-top:.15rem; font-size:var(--fs-16); }
.progress-card-heading > .material-symbols-outlined { color:var(--accent-ink); }
.progress-history .section-note { margin-top:var(--s-2); }
.progress-empty-history { min-height:12rem; }
.progress-next-card { display:flex; flex-direction:column; align-items:flex-start; min-height:16rem; }
.progress-next-card h3 { margin:var(--s-2) 0; font-size:var(--fs-20); }
.progress-next-card .section-note { max-width:45ch; }
.progress-next-card .stitch-btn { margin-top:auto; }
.progress-next-subject { margin-top:var(--s-4); color:var(--accent-ink); font-size:var(--fs-13); }
.progress-quiet-link { margin-top:var(--s-3); font-size:var(--fs-13); }
.progress-settings { max-width:none; margin-top:var(--s-6); padding:0; border:1px solid var(--line); border-radius:var(--r-md); background:var(--bg-elevated); }
.progress-settings summary { list-style:none; display:flex; align-items:center; justify-content:space-between; gap:var(--s-3); padding:var(--s-4); cursor:pointer; }
.progress-settings summary::-webkit-details-marker { display:none; }
.progress-settings summary > span:first-child { display:flex; align-items:center; gap:var(--s-3); }
.progress-settings summary .material-symbols-outlined { color:var(--text-muted); }
.progress-settings summary span span:last-child { display:grid; }
.progress-settings summary small { color:var(--text-muted); }
.progress-settings[open] .settings-chevron { transform:rotate(180deg); }
.danger-zone-body { display:flex; align-items:center; justify-content:space-between; gap:var(--s-4); padding:var(--s-4); border-top:1px solid var(--line); }
.danger-zone-body h3 { font-size:var(--fs-14); }
.danger-zone-body p { color:var(--text-muted); font-size:var(--fs-13); margin-top:.2rem; }
.stat-value { margin: 0; font-size: var(--fs-24); font-weight: 600; line-height: 1.2; font-variant-numeric: tabular-nums; }
.stat-label { font-size: var(--fs-12); color: var(--text-muted); }
.data-table { width: 100%; border-collapse: collapse; font-size: var(--fs-14); margin-top: var(--s-3); }
.data-table th { text-align: left; padding: 0.5rem 0.75rem 0.5rem 0; font-size: var(--fs-12); font-weight: 600; color: var(--text-muted); border-bottom: 1px solid var(--line-strong); }
.data-table td { padding: 0.25rem 0.75rem 0.25rem 0; border-bottom: 1px solid var(--line); }
.data-table .num { white-space: nowrap; font-variant-numeric: tabular-nums; }
.data-table .act { text-align: right; padding-right: 0; white-space: nowrap; }
.text-btn.danger { color: var(--danger-ink); }
.text-btn.danger:hover { background: rgba(248, 81, 73, 0.1); color: var(--danger-ink); }
.danger-zone { margin-top: var(--s-10); padding-top: var(--s-6); border-top: 1px solid var(--line); max-width: 46rem; }
.danger-zone .section-note { margin-bottom: var(--s-2); }
.danger-zone .text-btn { margin-left: calc(-1 * var(--s-2)); }

/* ============================================================
   Empty, toast, modal
   ============================================================ */
.empty-state { padding: var(--s-4) 0; max-width: 36rem; }
.empty-icon { font-size: 1.75rem; color: var(--text-faint); margin-bottom: var(--s-2); }
.empty-state .card-title { margin-bottom: 0.25rem; }
.toast {
  position: fixed; left: 50%; bottom: var(--s-6);
  transform: translate(-50%, 0.75rem);
  padding: 0.5rem 0.875rem; border-radius: var(--r-md);
  background: var(--surface-3); border: 1px solid var(--line-strong);
  color: var(--text); font-size: var(--fs-12); font-weight: 500;
  box-shadow: var(--shadow-2);
  opacity: 0; pointer-events: none; visibility: hidden;
  transition: opacity var(--ease), transform var(--ease), visibility var(--ease);
  z-index: 100;
}
.toast.show { opacity: 1; transform: translate(-50%, 0); visibility: visible; }
.modal-overlay {
  position: fixed; inset: 0; z-index: 90;
  display: flex; align-items: center; justify-content: center;
  padding: var(--s-4);
  background: rgba(1, 4, 9, 0.72);
  opacity: 0; visibility: hidden; pointer-events: none;
  transition: opacity var(--ease), visibility var(--ease);
}
.modal-overlay.active { opacity: 1; visibility: visible; pointer-events: auto; transition: opacity var(--ease); }
 /* visible at once so focus() on open works */
.modal-content {
  display: flex; flex-direction: column;
  width: 100%; max-width: 30rem; max-height: 85vh; max-height: min(85vh, 85dvh); overflow: hidden;
  background: var(--surface); border: 1px solid var(--line-strong);
  border-radius: var(--r-lg); box-shadow: var(--shadow-3);
  outline: none;
}
.modal-head {
  flex: 0 0 auto; display: flex; align-items: center; justify-content: space-between; gap: var(--s-3);
  padding: var(--s-3) var(--s-3) var(--s-3) var(--s-5); border-bottom: 1px solid var(--line);
}
.modal-title { font-size: var(--fs-16); font-weight: 600; }
.modal-body { flex: 1 1 auto; min-height: 0; overflow-y: auto; padding: var(--s-5); font-size: var(--fs-14); color: var(--text); line-height: 1.6; }
.modal-actions { flex: 0 0 auto; display: flex; flex-wrap: wrap; justify-content: flex-end; gap: var(--s-2); padding: var(--s-3) var(--s-5); border-top: 1px solid var(--line); }
.key-list { margin: 0; }
.key-list > div { display: grid; grid-template-columns: 7.5rem minmax(0, 1fr); gap: var(--s-3); padding: 0.5rem 0; border-bottom: 1px solid var(--line); }
.key-list > div:first-child { padding-top: 0; }
.key-list dt, .key-list dd { margin: 0; }
.key-list dd { color: var(--text-muted); }
kbd { display: inline-block; padding: 0 0.375rem; border: 1px solid var(--line-strong); border-radius: 0.25rem; background: var(--surface-2); font-family: var(--font-mono); font-size: var(--fs-12); line-height: 1.5; }
.modal-note { margin-top: var(--s-4); color: var(--text-muted); font-size: var(--fs-13); }

/* Mobile nav */
.sidebar-backdrop {
  position: fixed; inset: 0;
  background: rgba(1, 4, 9, 0.66);
  opacity: 0; visibility: hidden; pointer-events: none;
  transition: opacity var(--ease), visibility var(--ease);
  z-index: 35;
  backdrop-filter: blur(2px);
}
.sidebar-backdrop.visible { opacity: 1; visibility: visible; pointer-events: auto; }


/* ============================================================
   Responsive (rem breakpoints, so text zoom reflows the layout)
   ============================================================ */
@media (max-width: 68.75rem) {
  .dash-top, .dash-bottom { grid-template-columns: minmax(0, 1fr); }
  .dash-top { gap: 3rem; }
}

@media (max-width: 60rem) {
  .viz-workspace, .predict-layout, .analyzer-grid, .quest-layout { grid-template-columns: minmax(0, 1fr); }
  .quest-layout { gap: var(--s-8); }
  .quest-aside { position: static; max-width: none; padding-left: 0; border-left: 0; padding-top: var(--s-5); border-top: 1px solid var(--line); }
  .predict-layout { gap: var(--s-6); }
  .viz-tabs { min-width:0; flex:1 1 100%; }
  .viz-transport { align-items:stretch; }
  .transport-progress { flex:1 1 100%; min-width:0; flex-direction:row; align-items:center; }
  .transport-progress .progress-bar { flex:1 1 auto; }
  .transport-buttons { display:grid; grid-template-columns:repeat(4,minmax(0,1fr)); width:100%; min-width:0; }
  .transport-buttons .stitch-btn { min-width:0; justify-content:center; padding-left:.375rem; padding-right:.375rem; }
}

/* Descriptions are secondary; drop them before the row gets cramped. */
@media (max-width: 43.75rem) {
  .topic-desc { display: none; }
  .topic-row { grid-template-columns: minmax(0, 1fr); }
  .topic-meta { margin-left: calc(-1 * var(--s-2)); }
  .topic-score { margin: 0 var(--s-2); }
  .topic-meta .text-btn { padding: 0 var(--s-3); }
}

@media (max-width: 47.9375rem) {
  .mobile-only { display: inline-grid; }
  .icon-button.mobile-only { display: inline-grid; }
  .app-sidebar {
    position: fixed; top: 0; bottom: 0; left: 0;
    flex-basis: auto;
    transform: translateX(-100%);
    /* Hidden, not just translated: an off-screen drawer must not keep its
       buttons in the tab order or intercept clicks. */
    visibility: hidden;
    transition: transform 180ms ease, visibility 0s linear 180ms;
    border-right: 1px solid var(--line-strong);
    box-shadow: var(--shadow-3);
  }
  .stitch-sidebar.app-sidebar { width: min(86vw, 18.75rem); }
  .app-sidebar.open { transform: translateX(0); visibility: visible; transition: transform 180ms ease; }
  .screen-inner { padding: var(--s-5) var(--s-4) 3rem; }
  .screen-title { font-size: var(--fs-24); }
  .next-title { font-size: var(--fs-24); }
  .stitch-header.app-topbar { padding: 0 var(--s-3); }
  .brand { display: inline-flex; }
  /* The h1 stays in the accessibility tree; the brand takes its place visually. */
  .page-title {
    position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0;
    overflow: hidden; clip: rect(0, 0, 0, 0);
  }
  .stitch-header .row:first-child { flex: 1 1 auto; min-width: 0; }
  .action-grid { grid-template-columns: 1fr; }
  .chat-shell { max-width: none; }
  .chat-bubble { max-width: 90%; }
  .quest-node { grid-template-columns: minmax(0, 1fr); grid-template-areas: "name" "meta" "status"; row-gap: 0.125rem; }
  .quest-status { justify-content: flex-start; text-align: left; margin-top: var(--s-2); }
  .quest-start-cta { padding: 0.5rem 1.25rem; }
  .chat-log { padding: var(--s-4) var(--s-3); }
  .chat-head { padding: var(--s-4) var(--s-3) var(--s-3); }
  .suggestions { padding: 0 var(--s-3) var(--s-2); }
  .chat-composer { padding: var(--s-2) var(--s-3) var(--s-3); }

  /* Visualizer: the transport stays reachable at the bottom of the viewport. */
  .has-transport { padding-bottom: calc(7.25rem + env(safe-area-inset-bottom, 0px)); }
  .viz-transport {
    position: fixed; left: 0; right: 0; bottom: 0; z-index: 30;
    flex-direction: column; align-items: stretch; flex-wrap: nowrap; gap: var(--s-2);
    padding: var(--s-2) var(--s-3) calc(var(--s-2) + env(safe-area-inset-bottom, 0px));
    background: var(--bg-elevated); border: 0; border-top: 1px solid var(--line-strong); border-radius: 0;
  }
  .transport-progress { flex: 0 0 auto; flex-direction: row; align-items: center; gap: var(--s-3); }
  .transport-progress .progress-bar { flex: 1 1 auto; }
  .transport-buttons { display: grid; grid-template-columns: auto 1fr 1.4fr 1fr; gap: var(--s-2); }
  .transport-text { display: none; }
  .viz-code { max-height: 15rem; }
  .modal-actions { flex-direction: column-reverse; }
  .modal-actions .stitch-btn { width: 100%; }
  .key-list > div { grid-template-columns: 6rem minmax(0, 1fr); }
  .lesson-pager { grid-template-columns: 1fr; gap: var(--s-2); }
  .pager-link.next { grid-column: 1; text-align: left; }
}

/* The fixed desktop sidebar leaves tablet screens narrower than their viewport. */
@media (min-width: 47.9376rem) and (max-width: 50rem) {
  .progress-hero { grid-template-columns:minmax(0,1fr); }
  .progress-overall { grid-template-columns:auto minmax(0,1fr); justify-items:start; text-align:left; min-width:0; }
  .progress-ring { width:6rem; }
  .progress-stats { grid-template-columns:repeat(2,minmax(0,1fr)); gap:var(--s-4) 0; }
  .course-progress-grid { grid-template-columns:repeat(2,minmax(0,1fr)); }
  .progress-detail-grid { grid-template-columns:minmax(0,1fr); }
}

/* Touch: 44px minimum targets */
@media (max-width: 47.9375rem), (pointer: coarse) {
  .stitch-btn, .text-btn, .nav-item, .filter-chip, .viz-tab, .suggest-chip, .back-link,
  .input, .select, .text-input, .action-btn, .quest-node, .quiz-option, .transport-buttons .stitch-btn { min-height: var(--touch); }
  .plain-link, .data-table td a, .subject-name { display: inline-flex; align-items: center; min-height: var(--touch); }
  .icon-button { width: var(--touch); height: var(--touch); }
  .rail-row { min-height: var(--touch); }
  .tool-link { min-height: var(--touch); }
}

@media (max-width: 38.75rem) {
  .viz-tabs { width: 100%; overflow-x: auto; }
  .viz-topic { width: 100%; }
  .viz-topic .select { flex: 1 1 auto; min-width: 0; max-width: none; }
  .quiz-question { font-size: 1.125rem; }
  .result-score { font-size: 2.5rem; }
  .pane-head { flex-wrap: wrap; }
  .field-inline { flex: 1 1 100%; }
  .field-inline .select { flex: 1 1 auto; }
  .mem-row { grid-template-columns: 2rem 4rem minmax(0, 1fr); }
  .mem-points { grid-column: 3; }
  .stat-strip { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--s-3) var(--s-6); }
  .progress-page-head { align-items:flex-start; flex-direction:column; gap:var(--s-2); }
  .progress-hero { grid-template-columns:minmax(0,1fr); gap:var(--s-5); }
  .progress-overall { grid-template-columns:auto 1fr; justify-items:start; text-align:left; min-width:0; }
  .progress-ring { width:6rem; }
  .progress-ring strong { font-size:1.4rem; }
  .progress-stats { grid-template-columns:repeat(2,minmax(0,1fr)); gap:var(--s-4) 0; }
  .progress-stat { padding:0 var(--s-3); }
  .progress-stat:nth-child(odd) { padding-left:0; }
  .progress-stat:nth-child(even) { border:0; }
  .course-progress-grid { grid-template-columns:repeat(2,minmax(0,1fr)); }
  .progress-detail-grid { grid-template-columns:minmax(0,1fr); }
  .section-heading-row { align-items:flex-start; flex-direction:column; }
  .danger-zone-body { align-items:flex-start; flex-direction:column; }
  .code-textarea { min-height: 11.25rem; }
  .screen-heading { align-items: flex-start; }
  .next-actions .stitch-btn { flex: 1 1 100%; }
}

@media (max-width: 25rem) {
  .screen-inner { padding-left: var(--s-3); padding-right: var(--s-3); }
  .stat-value { font-size: var(--fs-20); }
  .stitch-btn { padding: 0.4375rem 0.6875rem; }
  .course-progress-link { padding:var(--s-3); }
  .progress-hero-actions { align-items:stretch; flex-direction:column; }
  .progress-hero-actions .stitch-btn { width:100%; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

/* Programmatic focus on a heading or screen is for screen readers; no ring. */
.screen:focus-visible, [tabindex="-1"]:focus-visible { outline: none; }
.rail-more { margin-left: 1.5rem; }
@media (max-width: 38.75rem) {
  .next-actions .stitch-btn + .text-btn { margin-left: calc(-1 * var(--s-2)); }
}