/* Students4AI calculus lab styles.
   Design principles (documented in README.md):
   - One fixed layout on every screen; navigation never moves.
   - Calm, low-saturation palette. Incorrect answers use amber ("not yet"),
     never alarm-red. Motion is controlled in the lab; no flashing or sound.
   - Explicit structure everywhere: numbered progress, visible rules,
     "you are here" breadcrumb on every view.
   - Strong focus outlines and full keyboard operability. */

:root {
  --bg: #f1f5fb;
  --surface: #ffffff;
  --surface-2: #eaf0f8;
  --text: #17283e;
  --muted: #53657b;
  --border: #ccd8e8;
  --accent: #275bc1;
  --accent-soft: #e8efff;
  --on-accent: #ffffff;
  --good: #166957;
  --good-soft: #e0f3eb;
  --notyet: #8a5a1d;
  --notyet-soft: #f6ecdc;
  --locked: #97a4b1;
  --shadow: 0 8px 24px rgba(25, 47, 82, 0.055);
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --font-scale: 1;
}
html[data-theme="dark"] {
  --bg: #0b1220;
  --surface: #111d30;
  --surface-2: #18273d;
  --text: #e6edf8;
  --muted: #a4b5cc;
  --border: #2c405b;
  --accent: #8db7ff;
  --accent-soft: #1c3151;
  --on-accent: #10203a;
  --good: #6de0bd;
  --good-soft: #133b35;
  --notyet: #efbd73;
  --notyet-soft: #3d3021;
  --locked: #66717c;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.18);
}
html[data-textsize="large"] { --font-scale: 1.15; }
html[data-textsize="xlarge"] { --font-scale: 1.3; }

* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  font-size: calc(16px * var(--font-scale));
  line-height: 1.65;
}

.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap;
}
.skip-link {
  position: absolute; left: -9999px; top: 0; background: var(--accent); color: #fff;
  padding: 0.5rem 1rem; z-index: 10; border-radius: 0 0 6px 0;
}
.skip-link:focus { left: 0; }

a { color: var(--accent); }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; border-radius: 3px; }

.app-header { background: var(--surface); border-bottom: 1px solid var(--border); }
.header-inner {
  max-width: 820px; margin: 0 auto; padding: 0.7rem 1rem;
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
}
.brand { font-weight: 700; font-size: 1.15em; text-decoration: none; color: var(--text); }
.app-header nav { display: flex; gap: 0.4rem; }
.app-header nav a {
  text-decoration: none; padding: 0.35rem 0.8rem; border-radius: 6px; color: var(--text);
  border: 1px solid transparent;
}
.app-header nav a.active { background: var(--accent-soft); border-color: var(--accent); font-weight: 600; }
.app-header nav a:hover { background: var(--surface-2); }

.app-main { max-width: 820px; margin: 0 auto; padding: 1rem 1rem 3rem; }
.breadcrumb { color: var(--muted); font-size: 0.9em; margin: 0.4rem 0 1rem; min-height: 1.4em; }
.breadcrumb strong { color: var(--text); }

.app-footer { border-top: 1px solid var(--border); color: var(--muted); }
.app-footer p { max-width: 820px; margin: 0 auto; padding: 0.8rem 1rem; font-size: 0.85em; }
.noscript-note { max-width: 820px; margin: 1rem auto; padding: 0 1rem; }

h1 { font-size: 1.5em; margin: 0.2rem 0 0.6rem; }
h2 { font-size: 1.2em; margin: 1.2rem 0 0.5rem; }
h3 { font-size: 1.05em; margin: 1rem 0 0.4rem; }
p { margin: 0.5rem 0; }

.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: 10px;
  padding: 1rem 1.2rem; margin: 0.8rem 0;
}
.card.subtle { background: var(--surface-2); }

button, .btn {
  font: inherit; cursor: pointer;
  background: var(--accent); color: var(--on-accent); border: 1px solid var(--accent);
  border-radius: 8px; padding: 0.55rem 1.1rem; text-decoration: none; display: inline-block;
}
button:hover, .btn:hover { filter: brightness(1.08); }
button:disabled { background: var(--locked); border-color: var(--locked); cursor: not-allowed; }
button.secondary, .btn.secondary {
  background: var(--surface); color: var(--accent); border-color: var(--accent);
}
button.quiet, .btn.quiet {
  background: transparent; color: var(--muted); border-color: var(--border);
}
button.secondary:disabled, button.quiet:disabled {
  background: var(--surface); color: var(--locked); border-color: var(--locked); cursor: not-allowed;
}
.btn-row { display: flex; flex-wrap: wrap; gap: 0.6rem; margin-top: 1rem; align-items: center; }

/* Unit map */
.unit-card { display: flex; gap: 1rem; align-items: flex-start; }
.unit-num {
  flex: 0 0 auto; width: 2.4rem; height: 2.4rem; border-radius: 50%;
  display: flex; align-items: center; justify-content: center; font-weight: 700;
  background: var(--accent-soft); color: var(--accent); border: 2px solid var(--accent);
}
.unit-card.locked .unit-num { background: var(--surface-2); color: var(--locked); border-color: var(--locked); }
.unit-card.passed .unit-num { background: var(--good-soft); color: var(--good); border-color: var(--good); }
.unit-body { flex: 1; }
.unit-title-row { display: flex; justify-content: space-between; gap: 0.6rem; flex-wrap: wrap; align-items: baseline; }
.unit-title-row h2 { margin: 0; }
.tag {
  font-size: 0.78em; padding: 0.1rem 0.55rem; border-radius: 999px;
  border: 1px solid var(--border); color: var(--muted); white-space: nowrap;
}
.tag.passed { background: var(--good-soft); color: var(--good); border-color: var(--good); }
.tag.locked { background: var(--surface-2); }
.tag.bc { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }

/* Progress bars — always paired with explicit numbers */
.bar-row { display: flex; align-items: center; gap: 0.7rem; margin: 0.3rem 0; }
.bar-label { flex: 0 0 14rem; font-size: 0.92em; }
.bar { flex: 1; height: 0.7rem; background: var(--surface-2); border-radius: 999px; border: 1px solid var(--border); overflow: hidden; }
.bar > span { display: block; height: 100%; background: var(--accent); }
.bar.done > span { background: var(--good); }
.bar-num { flex: 0 0 4.5rem; text-align: right; font-variant-numeric: tabular-nums; font-size: 0.92em; color: var(--muted); }

/* Question card */
.q-meta { color: var(--muted); font-size: 0.9em; display: flex; gap: 1rem; flex-wrap: wrap; }
.q-prompt { margin: 0.8rem 0; }
.choices { display: flex; flex-direction: column; gap: 0.55rem; margin: 0.8rem 0; }
.choice {
  text-align: left; background: var(--surface); color: var(--text);
  border: 2px solid var(--border); border-radius: 8px; padding: 0.6rem 0.9rem; width: 100%;
}
.choice:hover { border-color: var(--accent); background: var(--accent-soft); }
.choice[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); font-weight: 600; }
.choice.reveal-correct { border-color: var(--good); background: var(--good-soft); }
.choice.reveal-chosen { border-color: var(--notyet); background: var(--notyet-soft); }
.choice:disabled { cursor: default; filter: none; background: var(--surface); border-color: var(--border); color: var(--text); opacity: 0.75; }
.choice:disabled.reveal-correct { background: var(--good-soft); border-color: var(--good); opacity: 1; }
.choice:disabled.reveal-chosen { background: var(--notyet-soft); border-color: var(--notyet); opacity: 1; }
.choice-key { display: inline-block; min-width: 1.5em; font-weight: 700; color: var(--muted); }

.numeric-row { display: flex; gap: 0.6rem; align-items: center; flex-wrap: wrap; margin: 0.8rem 0; }
.numeric-row input {
  font: inherit; padding: 0.5rem 0.7rem; border: 2px solid var(--border); border-radius: 8px;
  width: 11rem; background: var(--surface); color: var(--text);
}
.numeric-hint { color: var(--muted); font-size: 0.88em; }

.feedback { border-radius: 10px; padding: 0.9rem 1.1rem; margin: 1rem 0; border: 2px solid; }
.feedback.good { border-color: var(--good); background: var(--good-soft); }
.feedback.notyet { border-color: var(--notyet); background: var(--notyet-soft); }
.feedback h3 { margin-top: 0; }

.hint-box { border-left: 4px solid var(--accent); background: var(--accent-soft); padding: 0.6rem 1rem; margin: 0.6rem 0; border-radius: 0 8px 8px 0; }
.solution-steps { margin: 0.6rem 0; padding-left: 0; list-style: none; counter-reset: step; }
.solution-steps li { margin: 0.7rem 0; padding-left: 2.2rem; position: relative; }
.solution-steps li::before {
  counter-increment: step; content: counter(step);
  position: absolute; left: 0; top: 0.1rem;
  width: 1.5rem; height: 1.5rem; border-radius: 50%; font-size: 0.85em;
  display: flex; align-items: center; justify-content: center;
  background: var(--accent-soft); color: var(--accent); font-weight: 700;
}
.step-math { margin: 0.3rem 0; overflow-x: auto; }

/* Lesson sections */
.section { margin: 1.1rem 0; }
.coder-note {
  border: 1px solid var(--accent); border-radius: 10px; padding: 0.8rem 1.1rem;
  background: var(--accent-soft);
}
.coder-note .kicker { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 0.85em; color: var(--accent); font-weight: 700; }
.worked-example { border: 1px solid var(--border); border-radius: 10px; padding: 0.8rem 1.1rem; background: var(--surface-2); }

.rules-list { margin: 0.5rem 0; padding-left: 1.4rem; }
.rules-list li { margin: 0.3rem 0; }

.whats-next { border-left: 4px solid var(--good); padding: 0.5rem 1rem; background: var(--good-soft); border-radius: 0 8px 8px 0; margin-top: 1rem; }
.whats-next .kicker { font-weight: 700; color: var(--good); font-size: 0.9em; }

.session-progress { font-variant-numeric: tabular-nums; color: var(--muted); }
.timer { color: var(--muted); font-variant-numeric: tabular-nums; }

table.simple { border-collapse: collapse; width: 100%; margin: 0.6rem 0; }
table.simple th, table.simple td { border: 1px solid var(--border); padding: 0.4rem 0.7rem; text-align: left; }
table.simple th { background: var(--surface-2); }

/* Interactive explorers — user-driven canvases, calm chrome */
.viz-box-outer { border: 1px solid var(--border); border-radius: 10px; padding: 0.8rem 1rem; margin: 0.8rem 0; background: var(--surface); }
.viz-title { margin: 0 0 0.6rem; font-size: 1em; }
.viz-graph canvas { max-width: 100%; border: 1px solid var(--border); border-radius: 8px; background: var(--surface); display: block; }
.viz-controls { margin: 0.7rem 0 0.3rem; display: flex; flex-direction: column; gap: 0.5rem; }
.viz-slider { display: flex; align-items: center; gap: 0.7rem; flex-wrap: wrap; }
.viz-slider-label { flex: 0 0 14rem; font-size: 0.92em; }
.viz-slider input[type="range"] { flex: 1; min-width: 10rem; accent-color: var(--accent); }
.viz-slider-out { flex: 0 0 4.5rem; text-align: right; font-variant-numeric: tabular-nums; color: var(--accent); font-weight: 600; }
.viz-btn-group { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.viz-mode-btn { background: var(--surface); color: var(--text); border: 2px solid var(--border); border-radius: 6px; padding: 0.3rem 0.8rem; font-size: 0.9em; }
.viz-mode-btn[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); font-weight: 600; }
.viz-readout { font-size: 0.92em; }
.viz-readout td { font-variant-numeric: tabular-nums; }
.viz-note { color: var(--muted); font-size: 0.92em; margin: 0.4rem 0 0; }
.viz-pipeline { display: flex; align-items: center; gap: 0.4rem; flex-wrap: wrap; font-size: 0.85em; margin-bottom: 0.6rem; color: var(--muted); }
.viz-pipeline .viz-box { border: 1px solid var(--accent); background: var(--accent-soft); color: var(--text); border-radius: 6px; padding: 0.15rem 0.5rem; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.explorer-details { border: 1px solid var(--border); border-radius: 8px; margin: 0.5rem 0; background: var(--surface-2); }
.explorer-details summary { cursor: pointer; padding: 0.55rem 0.9rem; font-weight: 600; }
.explorer-details summary:hover { background: var(--accent-soft); border-radius: 8px; }
.explorer-details .explorer-body { padding: 0 0.6rem 0.6rem; }
.feedback .viz-slot { margin-top: 0.8rem; }
.feedback .tutor-slot { margin-top: 0.8rem; }

/* AI tutor panel */
.tutor-panel { border: 1px solid var(--accent); border-radius: 10px; background: var(--surface); padding: 0.8rem 1rem; }
.tutor-panel h3 { margin-top: 0; }
.tutor-log { display: flex; flex-direction: column; gap: 0.6rem; }
.tutor-msg { border: 1px solid var(--border); border-radius: 8px; padding: 0.5rem 0.9rem; }
.tutor-msg.assistant { background: var(--accent-soft); border-color: var(--accent); }
.tutor-msg.user { background: var(--surface-2); }
.tutor-msg .tutor-who { display: block; font-size: 0.8em; font-weight: 700; color: var(--muted); margin-bottom: 0.2rem; }
.tutor-msg p { margin: 0.3rem 0; }
.tutor-status { color: var(--muted); font-size: 0.92em; min-height: 1.3em; }
.tutor-ask-row input { flex: 1; min-width: 14rem; }

/* Canvas plan and grades (read-only external data; calm, motion-free) */
.canvas-meta { color: var(--muted); font-size: 0.92em; margin: 0.3rem 0; }
.canvas-note { border-left: 4px solid var(--notyet); background: var(--notyet-soft); padding: 0.5rem 0.8rem; border-radius: 0 8px 8px 0; }
.canvas-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; flex-wrap: wrap; margin-bottom: 0.6rem; }
.canvas-tabs { display: flex; gap: 0.4rem; flex-wrap: wrap; margin-bottom: 0.8rem; }
.canvas-tabs a { padding: 0.3rem 0.8rem; border: 1px solid var(--border); border-radius: 8px; text-decoration: none; color: var(--text); }
.canvas-tabs a.active { border-color: var(--accent); background: var(--accent-soft); font-weight: 600; }
.canvas-form { display: grid; gap: 0.8rem; max-width: 38rem; }
.canvas-form label { display: grid; gap: 0.25rem; font-weight: 600; }
.canvas-form input[type="url"], .canvas-form input[type="password"] { font: inherit; padding: 0.5rem 0.7rem; border: 2px solid var(--border); border-radius: 8px; background: var(--surface); color: var(--text); }
.canvas-form .canvas-remember { display: flex; gap: 0.5rem; align-items: baseline; font-weight: 400; }
.canvas-terms { border: 1px solid var(--border); border-radius: 8px; padding: 0.6rem 0.9rem; margin: 0.6rem 0; background: var(--surface-2); }
.canvas-terms legend { font-weight: 600; padding: 0 0.3rem; }
.canvas-term { display: flex; gap: 0.5rem; align-items: baseline; margin: 0.25rem 0; }
.canvas-list { display: grid; gap: 0.6rem; margin-top: 0.6rem; }
.canvas-course-row { display: flex; gap: 0.4rem; align-items: stretch; }
.canvas-course-row .canvas-course { flex: 1; }
.canvas-course { display: flex; justify-content: space-between; gap: 1rem; align-items: center; padding: 0.65rem 0.75rem; border: 2px solid var(--border); border-radius: 8px; background: var(--surface); color: var(--text); text-decoration: none; }
.canvas-course:hover { border-color: var(--accent); background: var(--accent-soft); }
.canvas-course span { display: grid; }
.canvas-course small { color: var(--muted); font-size: 0.85em; }
.canvas-stats { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0.6rem; margin: 1rem 0; }
.canvas-stats div { display: grid; padding: 0.6rem; border: 1px solid var(--border); border-radius: 8px; background: var(--surface-2); }
.canvas-stats strong { font-variant-numeric: tabular-nums; color: var(--accent); }
.canvas-stats span { color: var(--muted); font-size: 0.82em; line-height: 1.35; }
.canvas-item { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: 0.65rem 0.75rem; border: 1px solid var(--border); border-radius: 8px; background: var(--surface); }
.canvas-item.attention { border-color: var(--notyet); background: var(--notyet-soft); }
.canvas-item > div { display: grid; gap: 0.15rem; }
.canvas-item-side { justify-items: end; text-align: right; }
.canvas-item .canvas-meta { margin: 0; }
.canvas-copy { white-space: pre-wrap; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 0.9em; background: var(--surface-2); border: 1px solid var(--border); border-radius: 8px; padding: 0.6rem 0.8rem; }
.canvas-assessment { border: 1px solid var(--accent); border-radius: 10px; background: var(--surface); padding: 0.8rem 1rem; }
.canvas-assessment p { margin: 0.4rem 0; }

.katex { font-size: 1.06em; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 0.2rem 0; }

@media (max-width: 640px) {
  .bar-label { flex-basis: 100%; }
  .bar-row { flex-wrap: wrap; }
  .header-inner { flex-direction: column; gap: 0.3rem; }
  .canvas-stats { grid-template-columns: 1fr; }
  .canvas-item { align-items: flex-start; flex-direction: column; }
  .canvas-item-side { justify-items: start; text-align: left; }
}

/* Stable workspace chrome: the same navigation and landmarks on every route. */
body {
  background-image: radial-gradient(circle at 1px 1px, var(--border) 0.6px, transparent 0.8px);
  background-size: 24px 24px;
}
.app-header { border-top: 3px solid var(--accent); }
.header-inner { max-width: 1140px; padding-top: 0.9rem; padding-bottom: 0.9rem; }
.brand { letter-spacing: -0.04em; font-size: 1.35em; white-space: nowrap; }
.app-header nav { flex-wrap: wrap; justify-content: center; gap: 0.3rem; }
.app-header nav a { font-size: 0.9em; font-weight: 600; border-radius: 8px; }
.app-header nav a.active { border-color: var(--border); color: var(--accent); }
.app-main { max-width: 1100px; padding-top: 1.3rem; }
.app-footer { background: var(--surface); }
.app-footer p { max-width: 1100px; }
.breadcrumb { font-family: var(--mono); font-size: 0.78em; }
h1 { font-size: clamp(1.7em, 3vw, 2.15em); line-height: 1.22; letter-spacing: -0.035em; margin-bottom: 0.7rem; }
h2 { letter-spacing: -0.02em; }
h3 { letter-spacing: -0.01em; }
.card { box-shadow: var(--shadow); border-radius: 14px; padding: 1.25rem 1.4rem; margin: 1rem 0; }
.card.subtle { box-shadow: none; }
button, .btn { font-weight: 600; border-radius: 9px; min-height: 42px; }
button:hover, .btn:hover { filter: none; box-shadow: inset 0 0 0 1px currentColor; }
button:disabled:hover { box-shadow: none; }
.choice:hover { box-shadow: none; }
.btn-row { gap: 0.55rem; }
.btn-row .btn, .btn-row button { font-size: 0.9em; }
input, select, textarea { accent-color: var(--accent); }
select {
  font: inherit; color: var(--text); background: var(--surface); border: 1px solid var(--border);
  border-radius: 8px; padding: 0.45rem 2rem 0.45rem 0.65rem; max-width: 100%; min-height: 42px;
}
input[type="range"] { min-height: 30px; }
input[type="checkbox"], input[type="radio"] { width: 1.1em; height: 1.1em; }
code { font-family: var(--mono); font-size: 0.92em; }
p code, li code { color: var(--accent); background: var(--accent-soft); padding: 0.1em 0.3em; border-radius: 4px; }
pre { overflow-x: auto; }
.tag { font-family: var(--mono); font-size: 0.69em; letter-spacing: 0.01em; padding: 0.2rem 0.55rem; }
.tag.bc, .tag.passed { border-color: transparent; }
.unit-card { position: relative; overflow: hidden; gap: 0.9rem; }
.unit-card::before { content: ''; position: absolute; inset: 0 auto 0 0; width: 3px; background: var(--accent); }
.unit-card.passed::before { background: var(--good); }
.unit-num {
  border-radius: 9px; width: 2.65rem; height: 2.65rem; border-width: 1px;
  font-family: var(--mono); font-size: 0.95em; background: var(--accent-soft);
}
.unit-body { min-width: 0; }
.unit-title-row h2 { font-size: 1.13em; line-height: 1.4; }
.unit-title-row h3 { margin: 0; font-size: 1.05em; line-height: 1.4; }
.unit-body > p { color: var(--muted); font-size: 0.92em; }
.unit-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.unit-grid .unit-card { margin: 0; }
.unit-grid .unit-title-row { align-items: flex-start; flex-direction: column; }
.unit-grid .bar-label { flex-basis: 100%; }
.unit-grid .bar-row { flex-wrap: wrap; }
.unit-grid .unit-body { display: flex; flex-direction: column; }
.unit-grid .unit-body > .btn-row { margin-top: auto; padding-top: 0.85rem; }
.bar { height: 0.5rem; border: 0; }
.bar > span { border-radius: inherit; }
.bar-num { font-family: var(--mono); font-size: 0.82em; }
.q-meta { font-family: var(--mono); font-size: 0.77em; padding-bottom: 0.8rem; border-bottom: 1px solid var(--border); }
.q-prompt { font-size: 1.05em; padding: 0.35rem 0; }
.choice { font-weight: 400; padding: 0.8rem 1rem; border-width: 1px; border-radius: 10px; }
.choice[aria-pressed="true"] { box-shadow: inset 3px 0 var(--accent); }
.choice-key { font-family: var(--mono); color: var(--accent); padding-right: 0.5rem; }
.feedback { border-width: 1px; border-left-width: 4px; }
.coder-note { border-color: var(--border); border-left: 4px solid var(--accent); }
.coder-note .kicker, .whats-next .kicker { font-family: var(--mono); font-size: 0.8em; }
.worked-example { border-radius: 12px; }
.rules-list { font-size: 0.95em; }
.canvas-tabs { padding: 0.25rem; background: var(--surface-2); border-radius: 10px; width: fit-content; }
.canvas-tabs a { border-color: transparent; font-size: 0.9em; font-weight: 600; }
.canvas-tabs a.active { background: var(--surface); border-color: var(--border); color: var(--accent); }
.canvas-course { border-width: 1px; border-radius: 11px; }
.canvas-item { border-radius: 10px; }
.canvas-stats div { border-radius: 10px; padding: 0.9rem 1rem; }
.canvas-stats strong { font-family: var(--mono); font-size: 1.4em; }
.canvas-terms { border-radius: 10px; }
table.simple { font-size: 0.9em; }
table.simple th { font-size: 0.88em; font-weight: 600; }
.viz-readout-wrap { overflow-x: auto; }
.viz-readout td { font-family: var(--mono); }
.viz-box-outer { border-radius: 12px; padding: 1rem; }
.viz-title { color: var(--text); letter-spacing: -0.015em; }
.viz-graph { overflow: hidden; }
.viz-graph canvas { width: 100%; margin: 0 auto; }
.viz-slider { padding: 0.5rem 0; }
.viz-slider-label { font-size: 0.85em; font-weight: 600; }
.viz-slider-out { font-family: var(--mono); font-size: 0.83em; }
.viz-playback { border-top: 1px solid var(--border); padding-top: 0.85rem; margin-top: 0.3rem; }
.viz-transport { display: flex; align-items: center; gap: 0.5rem; flex-wrap: wrap; }
.viz-transport button { font-size: 0.84em; padding: 0.4rem 0.95rem; min-width: 5.7rem; }
.viz-speed { display: flex; align-items: center; gap: 0.45rem; font-size: 0.8em; color: var(--muted); }
.viz-speed select { padding: 0.3rem 0.6rem; min-height: 36px; }
.viz-play-state { margin-left: auto; color: var(--muted); font-family: var(--mono); font-size: 0.73em; }
.viz-play-help { margin: 0.65rem 0 0; color: var(--muted); font-size: 0.76em; line-height: 1.6; }
.explorer-details { border-radius: 11px; }
.explorer-details summary { font-size: 0.9em; padding: 0.7rem 0.9rem; }

/* Astra has one predictable home below each question and its answer controls. */
.coach-card, .tutor-panel {
  margin-top: 1.2rem; padding: 1rem 1.1rem; min-width: 0;
  border: 1px solid var(--border); border-left: 3px solid var(--accent); border-radius: 12px;
  background: linear-gradient(120deg, var(--surface), var(--accent-soft));
  color: var(--text); overflow-wrap: anywhere;
}
.coach-card h3, .tutor-panel h3 { display: flex; align-items: center; gap: 0.55rem; margin: 0 0 0.5rem; font-size: 1.02em; line-height: 1.5; }
.coach-card h3::before, .tutor-panel h3::before {
  content: ''; display: inline-block; flex: 0 0 0.8rem; width: 0.8rem; height: 0.8rem;
  background: var(--accent); clip-path: polygon(50% 0, 64% 36%, 100% 50%, 64% 64%, 50% 100%, 36% 64%, 0 50%, 36% 36%);
}
.coach-card > p { max-width: 75ch; margin: 0.4rem 0; font-size: 0.86em; line-height: 1.65; color: var(--muted); }
.coach-card > .btn-row { margin: 0.85rem 0 0; }
.coach-card .tutor-open { min-height: 44px; padding: 0.55rem 0.85rem; color: var(--accent); background: var(--surface); border-color: var(--accent); }
.coach-card .tutor-open:hover { background: var(--accent-soft); box-shadow: none; }
.coach-card .tutor-open:disabled { color: var(--muted); border-color: var(--border); background: var(--surface-2); }
.tutor-panel > .viz-note { margin-bottom: 0.8rem; font-size: 0.8em; line-height: 1.6; }
.tutor-panel .btn-row { margin-top: 0.75rem; }
.tutor-hint-action {
  flex: 1 1 10rem; min-height: 42px; padding: 0.5rem 0.7rem;
  font-size: 0.8em; font-weight: 600; line-height: 1.4;
  color: var(--accent); background: var(--accent-soft); border: 1px solid var(--border);
}
.tutor-hint-action:hover { border-color: var(--accent); box-shadow: none; }
.tutor-hint-action:disabled { color: var(--muted); background: var(--surface-2); border-color: var(--border); }
.tutor-log { gap: 0.75rem; margin: 0.9rem 0 0; }
.tutor-log:empty { margin: 0; }
.tutor-msg { padding: 0.85rem 1rem; font-size: 0.92em; line-height: 1.75; overflow-wrap: anywhere; }
.tutor-msg.assistant { border-color: var(--border); background: var(--accent-soft); }
.tutor-msg.user { background: var(--surface-2); }
.tutor-msg .tutor-who { margin-bottom: 0.5rem; font: 600 0.75em var(--mono); color: var(--accent); letter-spacing: 0.04em; }
.tutor-msg.user .tutor-who { color: var(--muted); }
.tutor-msg p { max-width: 75ch; margin: 0.5rem 0; }
.tutor-msg p:last-child { margin-bottom: 0; }
.tutor-msg .katex-display { max-width: 100%; }
.tutor-status { min-height: 1.6em; margin: 0.75rem 0 0; font-size: 0.82em; line-height: 1.6; }
.tutor-ask-row { margin: 0.7rem 0 0; gap: 0.55rem; }
.tutor-ask-row input { flex: 1 1 16rem; min-width: 0; width: auto; max-width: 100%; padding: 0.65rem 0.75rem; font: inherit; border: 1px solid var(--border); border-radius: 9px; color: var(--text); background: var(--surface); }
.tutor-ask-row input::placeholder { color: var(--muted); opacity: 1; }
.tutor-send { flex: 0 0 auto; min-height: 44px; }

/* Page-wide help stays available at the bottom without covering the work. */
.page-coach {
  margin: 2rem 0 0.5rem; padding: 1.25rem; min-width: 0;
  border: 1px solid var(--border); border-top: 3px solid var(--accent); border-radius: 14px;
  color: var(--text); background: linear-gradient(125deg, var(--surface), var(--accent-soft)); box-shadow: var(--shadow);
}
.page-coach-heading { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 0.6rem; }
.page-coach-heading h3 { display: flex; align-items: center; gap: 0.55rem; margin: 0; font-size: 1.13em; line-height: 1.45; }
.page-coach-heading h3::before {
  content: ''; flex: 0 0 0.9rem; width: 0.9rem; height: 0.9rem; background: var(--accent);
  clip-path: polygon(50% 0, 64% 36%, 100% 50%, 64% 64%, 50% 100%, 36% 64%, 0 50%, 36% 36%);
}
.page-coach-tag { font: 600 0.65em/1.5 var(--mono); letter-spacing: 0.08em; color: var(--accent); }
.page-coach-intro { max-width: 76ch; margin: 0.65rem 0 0.4rem; font-size: 0.91em; color: var(--text); }
.page-coach-context { margin: 0.4rem 0 0.9rem; color: var(--muted); font: 0.76em/1.6 var(--mono); overflow-wrap: anywhere; }
.page-coach-quick { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0.5rem; margin: 0.85rem 0; }
.page-coach-quick button { flex: 1 1 12rem; min-height: 44px; padding: 0.55rem 0.75rem; font-size: 0.8em; line-height: 1.45; color: var(--accent); background: var(--surface); border-color: var(--border); }
.page-coach-quick button:hover { border-color: var(--accent); box-shadow: none; }
.page-coach-quick button:disabled { color: var(--muted); background: var(--surface-2); border-color: var(--border); }
.page-coach-log { display: grid; gap: 0.85rem; max-height: 31rem; overflow-y: auto; overscroll-behavior: contain; scrollbar-gutter: stable; margin: 1rem 0; padding-right: 0.4rem; }
.page-coach-log:empty { display: none; }
.page-coach-message { min-width: 0; padding: 0.85rem 1rem; border: 1px solid var(--border); border-radius: 10px; background: var(--surface); overflow-wrap: anywhere; }
.page-coach-message.user { background: var(--surface-2); }
.page-coach-message.is-pending { border-left: 3px solid var(--accent); }
.page-coach-message .page-coach-who { margin: 0 0 0.2rem; font: 600 0.74em/1.5 var(--mono); color: var(--accent); }
.page-coach-message.user .page-coach-who { color: var(--muted); }
.page-coach-message-context { margin: 0 0 0.6rem; font-size: 0.73em; color: var(--muted); }
.page-coach-message-content { font-size: 0.9em; line-height: 1.75; white-space: pre-wrap; }
.page-coach-message-content p { margin: 0.6rem 0; }
.page-coach-message-content p:first-child { margin-top: 0; }
.page-coach-message-content p:last-child { margin-bottom: 0; }
.page-coach-message-content pre { max-width: 100%; margin: 0.7rem 0; padding: 0.8rem; overflow: auto; border: 1px solid var(--border); border-radius: 7px; background: var(--surface-2); font: 0.84em/1.6 var(--mono); white-space: pre; }
.page-coach-message-content code { font-family: var(--mono); }
.page-coach-message-content h4, .page-coach-message-content h5, .page-coach-message-content h6 { margin: 1rem 0 0.45rem; font-size: 1.04em; line-height: 1.5; color: var(--text); }
.page-coach-message-content > :first-child { margin-top: 0; }
.page-coach-message-content ul, .page-coach-message-content ol { margin: 0.6rem 0; padding-left: 1.4rem; white-space: normal; }
.page-coach-message-content li + li { margin-top: 0.3rem; }
.page-coach-table-wrap { min-width: 0; max-width: 100%; overflow-x: auto; margin: 0.8rem 0; border: 1px solid var(--border); border-radius: 7px; white-space: normal; }
.page-coach-table-wrap:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.page-coach-table-wrap table { width: 100%; min-width: 24rem; margin: 0; border-collapse: collapse; font-size: 0.92em; }
.page-coach-table-wrap th, .page-coach-table-wrap td { min-width: 7rem; padding: 0.55rem 0.7rem; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); overflow-wrap: anywhere; }
.page-coach-table-wrap th { color: var(--text); background: var(--surface-2); font-weight: 600; }
.page-coach-table-wrap tbody tr:last-child td { border-bottom: 0; }
.page-coach-message-content .page-coach-table-note { font-size: 0.8em; color: var(--muted); }
.page-coach-message-content .katex-display { max-width: 100%; overflow-x: auto; }
.page-coach-sources { margin-top: 0.85rem; padding-top: 0.65rem; border-top: 1px solid var(--border); font-size: 0.78em; line-height: 1.65; }
.page-coach-sources > p { margin: 0; color: var(--muted); font-weight: 600; }
.page-coach-sources ul { padding-left: 1.2rem; margin: 0.35rem 0 0; }
.page-coach-sources li + li { margin-top: 0.25rem; }
.page-coach-source-detail { display: block; margin-top: 0.1rem; color: var(--muted); font-size: 0.95em; }
.page-coach-limitations { margin-top: 0.9rem; font-size: 0.79em; border: 1px solid var(--border); border-radius: 8px; background: var(--surface-2); }
.page-coach-limitations summary { padding: 0.5rem 0.7rem; color: var(--text); }
.page-coach-limitations ul { margin: 0.4rem 0.8rem 0.7rem; padding-left: 1.1rem; color: var(--muted); }
.page-coach-limitations li + li { margin-top: 0.3rem; }
.page-coach-remembered { margin: 0.7rem 0 0; color: var(--good); font-size: 0.79em; line-height: 1.65; }
.page-coach-links { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.9rem; }
.page-coach-links .btn { min-height: 44px; font-size: 0.79em; line-height: 1.5; white-space: normal; }
.page-coach-form { display: grid; gap: 0.45rem; margin-top: 1rem; }
.page-coach-form > label { color: var(--text); font-weight: 600; font-size: 0.87em; }
.page-coach-form textarea { display: block; width: 100%; max-width: 100%; min-height: 5.25rem; resize: vertical; padding: 0.7rem 0.85rem; font-family: inherit; font-size: 0.92em; line-height: 1.65; color: var(--text); background: var(--surface); border: 1px solid var(--border); border-radius: 9px; }
.page-coach-form textarea::placeholder { color: var(--muted); opacity: 1; }
.page-coach-form-actions { display: flex; flex-wrap: wrap; gap: 0.6rem; align-items: center; margin-top: 0.2rem; }
.page-coach-form-actions button { min-height: 44px; }
.page-coach-status { flex: 1 1 16rem; font-size: 0.8em; color: var(--muted); line-height: 1.6; }
.page-coach-status:empty { display: none; }
.page-coach-note { margin: 0.9rem 0 0; max-width: 90ch; font-size: 0.73em; line-height: 1.65; color: var(--muted); }
@media (max-width: 640px) {
  .page-coach { margin-top: 1.5rem; padding: 1rem; }
  .page-coach-heading { align-items: flex-start; }
  .page-coach-quick { grid-template-columns: minmax(0, 1fr); }
  .page-coach-quick button { flex-basis: 100%; text-align: left; }
  .page-coach-log { max-height: 27rem; padding-right: 0.2rem; }
  .page-coach-message { padding: 0.8rem; }
  .page-coach-form-actions button { flex: 1 1 auto; }
  .page-coach-status { flex-basis: 100%; }
  .page-coach-links .btn { flex: 1 1 100%; }
}

/* Course selection is a stable part of the dashboard, never a hidden filter. */
.course-switcher, .study-profile {
  display: flex; gap: 1rem; flex-wrap: wrap; align-items: center;
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
  padding: 0.9rem 1.1rem; margin: 1rem 0;
}
.course-switcher label, .study-profile label { display: grid; gap: 0.25rem; font-size: 0.82em; color: var(--muted); }
.course-switcher > label.study-profile, .course-switcher > label.course-switcher {
  display: grid; gap: 0.3rem; padding: 0; margin: 0; background: transparent; border: 0; border-radius: 0;
}
.course-switcher select, .study-profile select { font-weight: 600; min-width: 13rem; }
.course-select { min-width: 13rem; }
.open-status { color: var(--good); background: var(--good-soft); border: 1px solid var(--good); border-radius: 999px; padding: 0.2rem 0.6rem; font-family: var(--mono); font-size: 0.75em; }
.dashboard-hero { margin: 1rem 0; }
.dashboard-hero .kicker, .unit-grid > .card > .kicker { font: 600 0.7em var(--mono); letter-spacing: 0.08em; color: var(--accent); }
.dashboard-hero h1 { margin-top: 0.55rem; }
.dashboard-hero p { color: var(--muted); font-size: 0.92em; }
.dashboard-stats { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 0.8rem; margin: 1rem 0; }
.dashboard-stats > * { border: 1px solid var(--border); border-radius: 12px; background: var(--surface); padding: 1rem; }
.dashboard-stats strong { display: block; font: 700 1.65em var(--mono); color: var(--accent); }
.dashboard-stats strong small { font-size: 0.6em; }
.dashboard-stats span { color: var(--muted); font-size: 0.84em; }
.motion-setting { margin: 0.8rem 0; }
.motion-setting > label { display: block; margin: 0.5rem 0; }

/* Written AP responses keep equations and reasoning together at any width. */
.frq-card > .tag { white-space: normal; display: inline-block; }
.frq-part { margin: 1.2rem 0; padding-top: 0.25rem; border-top: 1px solid var(--border); }
.frq-part h4 { margin: 0.8rem 0 0.4rem; font-size: 0.95em; }
.frq-part label { display: block; color: var(--muted); font-size: 0.87em; }
.frq-part textarea {
  display: block; width: 100%; max-width: 100%; min-height: 9rem; resize: vertical;
  margin-top: 0.4rem; padding: 0.75rem 0.85rem; font: 0.95em/1.7 var(--mono);
  color: var(--text); background: var(--surface); border: 1px solid var(--border); border-radius: 9px;
}
.frq-part textarea::placeholder { color: var(--muted); opacity: 1; }
.frq-rubric { margin-top: 1rem; padding-top: 0.8rem; border-top: 1px solid var(--border); }
.rubric-item { display: block; margin: 0.5rem 0; padding: 0.7rem 0.8rem; background: var(--surface-2); border: 1px solid var(--border); border-radius: 8px; font-size: 0.91em; cursor: pointer; }
.rubric-item input { vertical-align: middle; margin-right: 0.4rem; }
.rubric-item .tag { display: inline-block; margin-left: 0.4rem; }
.self-score { font-family: var(--mono); font-size: 0.84em; padding: 0.7rem 0.8rem; background: var(--good-soft); color: var(--good); border-radius: 8px; }

/* A quiet study session: one next step, optional elapsed time, no urgency. */
.focus-planner { margin: 1rem 0; }
.focus-controls { display: flex; flex-wrap: wrap; align-items: flex-end; gap: 0.9rem; margin: 1rem 0; }
.focus-controls > label { display: grid; gap: 0.35rem; flex: 1 1 13rem; min-width: 0; font-size: 0.87em; color: var(--muted); }
.focus-controls label:has(input[type="checkbox"]) { display: flex; gap: 0.5rem; align-items: flex-start; }
.focus-controls select { width: 100%; min-width: 0; color: var(--text); }
.focus-controls input[type="text"], .focus-controls input[type="number"] { width: 100%; min-width: 0; font: inherit; color: var(--text); background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 0.6rem 0.75rem; }
.focus-next-step { border: 1px solid var(--border); border-left: 4px solid var(--accent); border-radius: 0 12px 12px 0; padding: 1rem 1.2rem; margin: 1.1rem 0; background: var(--accent-soft); }
.focus-next-step h2, .focus-next-step h3 { margin-top: 0; }
.focus-next-step .kicker { font: 600 0.74em var(--mono); letter-spacing: 0.06em; color: var(--accent); }
.focus-progress { display: grid; gap: 0.6rem; margin: 1rem 0; font: 0.84em/1.5 var(--mono); color: var(--muted); }
.focus-progress progress { appearance: none; width: 100%; height: 0.5rem; border: 0; border-radius: 999px; background: var(--surface-2); color: var(--good); overflow: hidden; }
.focus-progress progress::-webkit-progress-bar { background: var(--surface-2); border-radius: 999px; }
.focus-progress progress::-webkit-progress-value { background: var(--good); border-radius: 999px; }
.focus-progress progress::-moz-progress-bar { background: var(--good); border-radius: 999px; }
.focus-checklist { padding-left: 1.5rem; margin: 1rem 0; }
.focus-checklist li { margin: 0.6rem 0; padding-left: 0.3rem; }
.focus-checklist li::marker { font-family: var(--mono); color: var(--accent); }
.focus-checklist label { display: flex; align-items: flex-start; gap: 0.6rem; border: 1px solid var(--border); border-radius: 9px; padding: 0.8rem 0.9rem; background: var(--surface); font-size: 0.93em; cursor: pointer; }
.focus-checklist label:has(input:checked) { background: var(--good-soft); border-color: var(--good); }
.focus-checklist input { flex: 0 0 auto; margin-top: 0.25rem; }
.focus-checklist span { min-width: 0; }
.focus-actions { margin-top: 1rem; }
.focus-status { min-height: 1.6em; margin-top: 0.8rem; font-size: 0.86em; line-height: 1.6; color: var(--muted); }
.focus-entry { display: flex; align-items: center; justify-content: space-between; gap: 1rem; }
.focus-entry h2 { margin-top: 0; }
.focus-entry p { margin-bottom: 0; color: var(--muted); font-size: 0.9em; }
.focus-entry > .btn { flex-shrink: 0; }

/* Optional native 3D exploration; its render loop runs only on request. */
.spatial-lab { padding: 1rem; border: 1px solid var(--border); border-radius: 12px; background: var(--surface); }
.spatial-heading { display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem; }
.spatial-heading h3 { margin: 0 0 0.5rem; font-size: 1.1em; line-height: 1.4; }
.spatial-heading .lab-eyebrow { font-size: 0.64em; }
.spatial-heading .viz-note { font-size: 0.82em; max-width: 76ch; }
.spatial-renderer { flex-shrink: 0; color: var(--good); background: var(--good-soft); border-color: var(--good); }
.spatial-equation { display: flex; align-items: center; flex-wrap: wrap; gap: 0.6rem 1.2rem; margin: 0.9rem 0; font-size: 0.86em; }
.spatial-equation code { white-space: normal; }
.spatial-equation > span { font: 0.85em var(--mono); color: var(--muted); }
.spatial-graph { width: 100%; overflow: hidden; border: 1px solid var(--border); border-radius: 10px; touch-action: none; cursor: grab; }
.spatial-graph:active { cursor: grabbing; }
.spatial-graph canvas { display: block; width: 100%; max-width: 100%; }
.spatial-axis-key { display: flex; flex-wrap: wrap; gap: 0.55rem 1rem; margin: 0.65rem 0; font: 0.68em var(--mono); }
.spatial-axis-key span { display: inline-flex; align-items: center; gap: 0.35rem; }
.spatial-axis-key span::before { content: ''; width: 15px; height: 3px; border-radius: 2px; background: currentColor; }
.spatial-axis-x { color: var(--accent); }
.spatial-axis-y { color: var(--good); }
.spatial-axis-z { color: var(--muted); }
.spatial-axis-v { color: var(--notyet); }
.spatial-interaction-note, .spatial-explanation { font-size: 0.82em; line-height: 1.65; color: var(--muted); }
.spatial-controls { margin: 0.8rem 0; }
.spatial-camera { display: grid; grid-template-columns: 1fr 1fr; gap: 0.8rem; }
.spatial-camera .viz-slider { gap: 0.4rem; }
.spatial-camera .viz-slider-label { flex-basis: 100%; }
.spatial-camera input[type="range"] { min-width: 4rem; }
.spatial-camera .viz-slider-out { flex-basis: 3.8rem; }
.spatial-metrics { display: grid; grid-template-columns: 1fr 1fr 0.8fr; border: 1px solid var(--border); border-radius: 9px; background: var(--surface-2); }
.spatial-metrics > div { padding: 0.75rem; min-width: 0; display: grid; gap: 0.2rem; }
.spatial-metrics > div + div { border-left: 1px solid var(--border); }
.spatial-metrics span { color: var(--muted); font: 0.66em/1.4 var(--mono); }
.spatial-metrics strong { font: 600 0.8em/1.6 var(--mono); overflow-wrap: anywhere; }
.spatial-challenge { border-left: 3px solid var(--good); border-radius: 0 7px 7px 0; background: var(--good-soft); padding: 0.7rem 0.9rem; font-size: 0.83em; }

/* The coding workbench pairs all motion with inspectable calculations. */
.study-lab {
  margin: 1.3rem 0 1.8rem; padding: 1.4rem; border: 1px solid var(--border); border-radius: 18px;
  background: linear-gradient(130deg, var(--surface), var(--surface-2)); box-shadow: var(--shadow);
  overflow: hidden;
}
.lab-heading { display: flex; justify-content: space-between; gap: 1rem; align-items: flex-start; }
.lab-eyebrow { margin: 0 0 0.55rem; font: 600 0.68em var(--mono); letter-spacing: 0.13em; color: var(--accent); }
.lab-heading h2 { margin: 0; font-size: clamp(1.65em, 3.4vw, 2.45em); line-height: 1.16; letter-spacing: -0.045em; }
.lab-intro { color: var(--muted); font-size: 0.88em; margin: 0.65rem 0 0; }
.lab-course-tag { font: 600 0.66em var(--mono); padding: 0.4rem 0.65rem; color: var(--good); background: var(--good-soft); border: 1px solid var(--good); border-radius: 6px; white-space: nowrap; }
.lab-modes { display: flex; gap: 0.4rem; flex-wrap: wrap; margin: 1.2rem 0 0.85rem; }
.lab-mode { font: 500 0.73em var(--mono); background: transparent; color: var(--muted); border: 1px solid var(--border); padding: 0.45rem 0.7rem; min-height: 36px; border-radius: 7px; }
.lab-mode[aria-pressed="true"] { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }
.lab-workspace { display: grid; grid-template-columns: minmax(0, 1.4fr) minmax(260px, 1fr); border: 1px solid var(--border); border-radius: 11px; overflow: hidden; background: var(--surface); }
.lab-visual { min-width: 0; overflow: hidden; }
.lab-pane-title { display: flex; justify-content: space-between; gap: 0.5rem; flex-wrap: wrap; padding: 0.65rem 0.85rem; border-bottom: 1px solid var(--border); font: 500 0.6em var(--mono); letter-spacing: 0.055em; color: var(--muted); background: var(--surface-2); min-height: 35px; }
.lab-visual canvas { display: block; max-width: 100%; }
.lab-console { display: flex; flex-direction: column; min-width: 0; border-left: 1px solid var(--border); }
.lab-console pre { margin: 0; padding: 1rem; color: var(--accent); font: 0.7em/1.65 var(--mono); flex: 1; tab-size: 2; min-height: 282px; white-space: pre-wrap; overflow-wrap: anywhere; }
.lab-console pre code { font: inherit; }
.lab-metrics { display: grid; grid-template-columns: 1fr 1fr; border-top: 1px solid var(--border); background: var(--surface-2); }
.lab-metrics > div { display: grid; gap: 0.15rem; padding: 0.7rem 0.8rem; min-width: 0; }
.lab-metrics > div + div { border-left: 1px solid var(--border); }
.lab-metrics span { font: 0.61em/1.4 var(--mono); color: var(--muted); }
.lab-metrics strong { font: 600 0.94em/1.45 var(--mono); color: var(--text); overflow-wrap: anywhere; }
.lab-legend { display: flex; gap: 1rem; flex-wrap: wrap; padding: 0.5rem 0.9rem 0.9rem; color: var(--muted); font-size: 0.68em; }
.lab-legend span { display: inline-flex; align-items: center; gap: 0.4rem; }
.lab-legend i { display: inline-block; width: 17px; height: 3px; border-radius: 2px; background: var(--accent); }
.lab-legend .legend-tangent { background: var(--notyet); }
.lab-control-area { margin-top: 0.8rem; }
.lab-control-area .viz-slider { margin: 0; }
.lab-control-area .viz-slider-label { flex-basis: 12rem; }
.lab-control-area .viz-slider-out { flex-basis: 7rem; }
.lab-explanation { font-size: 0.83em; color: var(--muted); margin: 1rem 0 0; }
.lab-challenge { display: flex; gap: 0.8rem; align-items: baseline; padding: 0.8rem 1rem; margin-top: 0.9rem; border-left: 3px solid var(--good); background: var(--good-soft); border-radius: 0 8px 8px 0; font-size: 0.82em; }
.lab-challenge-label { font: 700 0.78em var(--mono); letter-spacing: 0.08em; color: var(--good); flex-shrink: 0; }

/* Only short interaction feedback is animated in full mode; no flashing. */
html[data-motion="full"] button,
html[data-motion="full"] .btn,
html[data-motion="full"] .app-header nav a { transition: background-color 140ms ease, border-color 140ms ease, box-shadow 140ms ease; }
html[data-motion="reduced"] *, html[data-motion="off"] * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
@media (prefers-reduced-motion: reduce) {
  html:not([data-motion="full"]) * { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}
@media (max-width: 800px) {
  .unit-grid { grid-template-columns: 1fr; }
  .lab-workspace { grid-template-columns: minmax(0, 1fr); }
  .lab-console { border-left: 0; border-top: 1px solid var(--border); }
  .lab-console pre { min-height: auto; font-size: 0.75em; }
  .lab-heading { flex-direction: column; gap: 0.7rem; }
  .lab-course-tag { order: -1; }
  .dashboard-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .study-lab { display: flex; flex-direction: column; }
  .lab-heading { order: 0; }
  .lab-modes { order: 1; }
  .lab-control-area { order: 2; margin: 0 0 1rem; }
  .lab-workspace { order: 3; }
  .lab-explanation { order: 4; }
  .lab-challenge { order: 5; }
}
@media (max-width: 640px) {
  .header-inner { padding: 0.7rem 0.65rem; }
  .app-header nav { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); width: 100%; gap: 0.2rem; }
  .app-header nav a { display: flex; align-items: center; justify-content: center; text-align: center; min-height: 44px; padding: 0.4rem 0.2rem; font-size: 0.78em; }
  .app-main { padding: 0.85rem 0.75rem 2rem; }
  .card { padding: 1rem; }
  .study-lab { padding: 1rem; border-radius: 13px; }
  .unit-card { gap: 0.7rem; }
  .unit-num { width: 2.1rem; height: 2.1rem; }
  .viz-slider-label, .lab-control-area .viz-slider-label { flex-basis: 100%; }
  .viz-slider input[type="range"] { min-width: 6rem; }
  .lab-control-area .viz-slider-out { flex-basis: 6rem; }
  .viz-play-state { margin-left: 0; }
  .lab-challenge { flex-direction: column; gap: 0.3rem; }
  .dashboard-stats { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .course-switcher, .study-profile { align-items: stretch; }
  .course-switcher label, .study-profile label { flex: 1 1 100%; }
  .course-switcher select, .study-profile select { min-width: 0; width: 100%; }
  .canvas-course-row { flex-wrap: wrap; }
  .canvas-course-row .canvas-course { flex-basis: 100%; }
  .coach-card, .tutor-panel { padding: 0.9rem; }
  .coach-card .tutor-open { width: 100%; text-align: left; }
  .tutor-hint-action { flex-basis: 100%; text-align: left; }
  .tutor-msg { padding: 0.75rem; }
  .tutor-ask-row input { flex-basis: 100%; }
  .tutor-send { width: 100%; }
  .spatial-lab { padding: 0.85rem; }
  .spatial-heading { flex-direction: column; gap: 0.5rem; }
  .spatial-camera { grid-template-columns: 1fr; gap: 0; }
  .spatial-metrics { grid-template-columns: 1fr; }
  .spatial-metrics > div + div { border-left: 0; border-top: 1px solid var(--border); }
  .focus-controls { align-items: stretch; }
  .focus-controls > label { flex-basis: 100%; }
  .focus-next-step { padding: 0.9rem; }
  .focus-checklist { padding-left: 1.2rem; }
  .focus-checklist label { padding: 0.7rem; }
  .focus-entry { flex-direction: column; align-items: stretch; }
  .focus-entry > .btn { align-self: flex-start; }
}