/* Shell contract: app.js replaces #app, wires header controls and clears
   #shell-status. Dynamic screens reuse these primitives; no study state is CSS-generated. */
:root {
  color-scheme: light;
  --page: var(--tg-theme-secondary-bg-color, #f6f5f1);
  --surface: var(--tg-theme-bg-color, #fffefa);
  --ink: var(--tg-theme-text-color, #242a31);
  --muted: var(--tg-theme-subtitle-text-color, #62676f);
  --accent: #245cc6;
  --on-accent: #ffffff;
  --wash: #eaf0fb;
  --soft: #eeede8;
  --line: #d9d8d2;
  --control-line: #858990;
  --danger: #a02f32;
  --danger-wash: #fbecea;
  --shadow: 0 2px 5px #242a3105, 0 12px 28px #242a3105;
  --radius-sm: 10px;
  --radius: 18px;
  --radius-lg: 24px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --safe-top: max(env(safe-area-inset-top, 0px), var(--tg-safe-area-inset-top, 0px));
  --safe-bottom: max(env(safe-area-inset-bottom, 0px), var(--tg-safe-area-inset-bottom, 0px));
  --safe-left: max(env(safe-area-inset-left, 0px), var(--tg-safe-area-inset-left, 0px));
  --safe-right: max(env(safe-area-inset-right, 0px), var(--tg-safe-area-inset-right, 0px));
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 17px;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
  -webkit-text-size-adjust: 100%;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --page: var(--tg-theme-secondary-bg-color, #191c20);
    --surface: var(--tg-theme-bg-color, #22262b);
    --ink: var(--tg-theme-text-color, #f1f0eb);
    --muted: var(--tg-theme-subtitle-text-color, #b3b7bf);
    --accent: #9dbdff;
    --on-accent: #112951;
    --wash: #2b3850;
    --soft: #2d3238;
    --line: #42484f;
    --control-line: #959ba5;
    --danger: #ffb4af;
    --danger-wash: #492d30;
    --shadow: none;
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --page: var(--tg-theme-secondary-bg-color, #191c20);
  --surface: var(--tg-theme-bg-color, #22262b);
  --ink: var(--tg-theme-text-color, #f1f0eb);
  --muted: var(--tg-theme-subtitle-text-color, #b3b7bf);
  --accent: #9dbdff;
  --on-accent: #112951;
  --wash: #2b3850;
  --soft: #2d3238;
  --line: #42484f;
  --control-line: #959ba5;
  --danger: #ffb4af;
  --danger-wash: #492d30;
  --shadow: none;
}

*, *::before, *::after { box-sizing: border-box; }
body { margin: 0; background: var(--page); color: var(--ink); line-height: 1.5; }
[hidden] { display: none !important; }
button, input, select, textarea { font: inherit; }
button, a, summary { -webkit-tap-highlight-color: transparent; touch-action: manipulation; }
button { color: inherit; cursor: pointer; }
button:disabled { cursor: not-allowed; }
a { color: var(--accent); text-underline-offset: 4px; }
svg { display: block; max-width: 100%; }
figure, p, h1, h2, h3, dl, dd { margin: 0; }
h1, h2, h3 { line-height: 1.2; font-weight: 650; text-wrap: balance; }
h1 { font-size: clamp(1.7rem, 5.6vw, 2.15rem); letter-spacing: -.035em; }
h2 { font-size: 1.15rem; letter-spacing: -.02em; }
h3 { font-size: 1rem; }
p, h1, h2, h3, a, button, dd { overflow-wrap: anywhere; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 4px; }
#app:focus { outline: none; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }
.skip-link { position: fixed; z-index: 20; top: 8px; left: 16px; padding: 12px 16px; border-radius: var(--radius-sm); background: var(--surface); transform: translateY(-160%); }
.skip-link:focus { transform: translateY(0); }
.app-shell { width: 100%; max-width: 640px; min-height: 100vh; min-height: 100dvh; margin-inline: auto; padding: calc(var(--safe-top) + var(--tg-content-safe-area-inset-top, 0px)) max(var(--space-5), var(--safe-right)) calc(var(--safe-bottom) + var(--tg-content-safe-area-inset-bottom, 0px)) max(var(--space-5), var(--safe-left)); display: flex; flex-direction: column; }
.app-header { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: var(--space-3); padding-block: var(--space-5); border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: var(--space-3); min-width: 0; }
.brand-mark { flex: 0 0 28px; width: 28px; height: 28px; fill: none; stroke: var(--ink); stroke-width: 1.8; stroke-linecap: round; }
.brand-copy { display: grid; gap: 2px; font-size: .82rem; font-weight: 650; line-height: 1.3; }
.brand-caption { font-size: .7rem; color: var(--muted); font-weight: 400; }
.language-switch { display: flex; flex: 0 0 auto; padding: 3px; border: 1px solid var(--line); border-radius: 14px; background: var(--soft); }
.language-switch button { min-width: 48px; min-height: 48px; padding: 8px; border: 0; border-radius: 10px; background: transparent; font-size: .76rem; font-weight: 650; color: var(--muted); }
.language-switch [aria-pressed="true"] { background: var(--surface); color: var(--ink); box-shadow: 0 1px 3px #00000012; text-decoration: underline; text-underline-offset: 5px; }
.screen-nav { display: flex; align-items: center; justify-content: space-between; gap: var(--space-3); padding-top: var(--space-3); }
#app { flex: 1; min-width: 0; }
.screen { display: grid; gap: var(--space-6); padding-block: var(--space-8); }
.screen-heading { display: grid; gap: var(--space-3); }
.eyebrow { color: var(--muted); font-size: .69rem; font-weight: 650; letter-spacing: .06em; line-height: 1.4; }
.lede { color: var(--muted); max-width: 48ch; font-size: 1rem; line-height: 1.6; }
.caption, figcaption { color: var(--muted); font-size: .76rem; line-height: 1.5; }
.text-label { font-size: .88rem; font-weight: 650; line-height: 1.4; }
.muted { color: var(--muted); }
.stack { display: grid; gap: var(--space-4); }
.cluster { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-3); }
.section-heading { display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: var(--space-2); }
.welcome-families { display: grid; gap: var(--space-3); }
.welcome-family { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); align-items: center; gap: var(--space-4); padding: var(--space-5); background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.family-copy { display: grid; gap: var(--space-2); }
.family-copy h2 { font-size: 1.02rem; }
.family-copy p { color: var(--muted); font-size: .82rem; line-height: 1.5; }
.welcome-illustration { display: grid; align-content: center; gap: var(--space-2); }
.welcome-illustration .diagram { width: 100%; max-width: 180px; margin-inline: auto; }
.welcome-illustration figcaption { text-align: center; font-size: .64rem; }
.notice { display: flex; align-items: flex-start; gap: var(--space-3); padding: var(--space-4); border: 1px solid var(--line); border-radius: var(--radius); background: var(--soft); }
.notice p { color: var(--muted); font-size: .82rem; }
.notice h2 + p { margin-top: var(--space-1); }
.icon { width: 20px; height: 20px; flex: 0 0 20px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.notice > .icon { margin-top: 2px; }
.welcome-actions { display: grid; gap: var(--space-3); text-align: center; }
.text-link { display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: var(--space-2); font-size: .88rem; }
.button { display: inline-flex; justify-content: center; align-items: center; gap: var(--space-3); min-height: 48px; padding: 12px 18px; border: 1px solid var(--control-line); border-radius: var(--radius-sm); background: var(--surface); color: var(--ink); font-weight: 600; font-size: .94rem; text-align: center; text-decoration: none; line-height: 1.4; transition: opacity 120ms ease; }
.button-primary { background: var(--accent); color: var(--on-accent); border-color: transparent; min-height: 54px; }
.button-quiet { background: transparent; border-color: transparent; color: var(--accent); }
.button-danger { color: var(--danger); background: var(--danger-wash); border-color: var(--danger); }
.button-block { width: 100%; }
.button:disabled, .answer-card:disabled { background: var(--soft); color: var(--muted); border-color: var(--line); box-shadow: none; }
.button:active:not(:disabled), .answer-card:active:not(:disabled), .family-tile:active:not(:disabled) { opacity: .7; }
.shell-status { padding-inline: var(--space-3); }
.privacy-panel { border-block: 1px solid var(--line); }
.privacy-panel summary { padding: var(--space-4) var(--space-1); min-height: 48px; cursor: pointer; font-size: .88rem; font-weight: 600; }
.privacy-panel .prose { padding: 0 var(--space-1) var(--space-5); }
.prose { display: grid; gap: var(--space-4); max-width: 65ch; font-size: .94rem; }
.prose p { line-height: 1.65; }
.app-footer { display: flex; justify-content: space-between; flex-wrap: wrap; gap: var(--space-2); padding-block: var(--space-5); border-top: 1px solid var(--line); color: var(--muted); font-size: .7rem; }

.panel, .family-tile, .tutorial-step, .history-item, .report-card { padding: var(--space-5); border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.family-grid { display: grid; gap: var(--space-3); }
.family-tile { display: grid; grid-template-columns: 48px minmax(0, 1fr) auto; align-items: center; gap: var(--space-4); min-height: 96px; text-align: start; }
.family-tile .diagram { width: 48px; height: 48px; }
.family-tile-copy { display: grid; gap: var(--space-1); }
.gate-count, .badge { display: inline-flex; align-items: center; gap: var(--space-2); padding: 4px 9px; border-radius: 8px; background: var(--soft); font-size: .76rem; font-weight: 600; font-variant-numeric: tabular-nums; }
.family-tile[aria-current="step"], .family-tile[aria-pressed="true"] { background: var(--wash); }
.family-tile:disabled { color: var(--muted); cursor: not-allowed; }
.active-session { display: grid; gap: var(--space-4); background: var(--wash); }
.action-row { display: flex; flex-wrap: wrap; gap: var(--space-3); }
.action-row > .button { flex: 1 1 130px; }
.stepper { display: flex; gap: var(--space-2); padding: 0; margin: 0; list-style: none; counter-reset: step; }
.stepper li { flex: 1; display: flex; align-items: center; gap: var(--space-2); min-width: 0; font-size: .76rem; color: var(--muted); counter-increment: step; }
.stepper li::before { content: counter(step); display: grid; place-items: center; width: 28px; height: 28px; flex: 0 0 28px; border: 1px solid var(--control-line); border-radius: 50%; font-variant-numeric: tabular-nums; }
.stepper [aria-current="step"] { color: var(--ink); font-weight: 650; }
.stepper [aria-current="step"]::before { background: var(--ink); color: var(--surface); }
.tutorial-step { display: grid; gap: var(--space-4); }
.storyboard { display: grid; gap: var(--space-4); }
.example-pair { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-3); }
.example, .counterexample { display: grid; align-content: start; gap: var(--space-3); padding: var(--space-3); background: var(--soft); border-radius: var(--radius-sm); }
.example-label { display: flex; align-items: center; gap: var(--space-2); font-size: .82rem; font-weight: 600; }

/* SVG primitives: bit-on is solid, bit-off is outlined; never color alone.
   Token mapping everywhere: 0 circle, 1 triangle, 2 square, 3 diamond. */
.diagram { color: var(--ink); overflow: visible; }
.diagram text { fill: var(--ink); font-family: inherit; font-size: 14px; }
.bit { fill: var(--surface); stroke: var(--ink); stroke-width: 1.8; }
.bit-on, .bit[data-value="1"] { fill: var(--ink); }
.bit-off, .bit[data-value="0"] { fill: var(--surface); }
.flow-line, .flow-arrow { fill: none; stroke: var(--control-line); stroke-width: 1.5; stroke-linecap: round; stroke-linejoin: round; }
.mask-panel { fill: var(--wash); stroke: var(--control-line); stroke-width: 1; }
.mask-mark { fill: none; stroke: var(--accent); stroke-width: 2; stroke-linecap: round; }
.mask-dot, .landmark { fill: var(--control-line); }
.token { fill: var(--surface); stroke: var(--ink); stroke-width: 2; stroke-linejoin: round; }
.slot { fill: none; stroke: var(--control-line); stroke-width: 1.5; stroke-linejoin: round; }
.diagram-row { display: flex; align-items: center; justify-content: center; gap: var(--space-3); min-width: 0; }
.diagram-row > svg { flex: 1 1 0; min-width: 0; }
.machine-examples, .switches-states, .placement-constraints { display: grid; gap: var(--space-4); }
.machine-query { padding-top: var(--space-4); border-top: 1px solid var(--line); }
.switch-masks { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-3); }
.switch-mask { display: grid; gap: var(--space-2); padding: var(--space-3); border: 1px solid var(--control-line); border-radius: var(--radius-sm); }
.switch-set { display: flex; flex-wrap: wrap; justify-content: center; gap: var(--space-2); }
.switch-label { display: grid; place-items: center; min-width: 28px; min-height: 28px; padding: 2px 6px; border: 1px solid var(--control-line); border-radius: 6px; font-size: .82rem; font-weight: 650; }
.switch-label[aria-checked="true"], .switch-label.is-selected { background: var(--ink); color: var(--surface); }
.constraint { display: flex; align-items: center; flex-wrap: wrap; gap: var(--space-3); }
.constraint svg { width: 36px; height: 36px; }
.task-legend { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-3) var(--space-4); padding: var(--space-3) var(--space-4); border: 1px solid var(--line); border-radius: var(--radius-sm); background: var(--surface); font-size: .76rem; }
.legend-item { display: inline-flex; align-items: center; gap: var(--space-2); }
.legend-item svg { width: 24px; height: 24px; flex-shrink: 0; }

/* Timing protection: the ready/loading state never reveals a stimulus.
   JS must also defer inserting a trial until the user explicitly requests it. */
.task-screen { gap: var(--space-5); }
.task-header { display: flex; align-items: center; flex-wrap: wrap; justify-content: space-between; gap: var(--space-3); }
.task-progress { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-2); color: var(--muted); font-size: .82rem; font-variant-numeric: tabular-nums; }
.progress-dots { display: flex; flex-wrap: wrap; gap: 5px; }
.progress-dot { width: 7px; height: 7px; border: 1px solid var(--control-line); border-radius: 50%; }
.progress-dot.is-complete { background: var(--ink); border-color: var(--ink); }
.progress-dot[aria-current="step"] { outline: 2px solid var(--ink); outline-offset: 2px; }
.ready-screen, .empty-state, .network-retry { display: grid; justify-items: center; gap: var(--space-5); padding: var(--space-8) var(--space-5); text-align: center; }
.ready-screen > .icon, .empty-state > .icon, .network-retry > .icon { width: 40px; height: 40px; }
.ready-screen p, .empty-state p, .network-retry p { max-width: 42ch; color: var(--muted); }
.task-stimulus { display: grid; gap: var(--space-5); padding: var(--space-5); border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.task-stimulus > .diagram { width: 100%; }
:is([data-state="ready"], [data-state="loading"], .ready-screen) :is(.task-stimulus, .answer-grid, [data-stimulus]) { display: none !important; }
.answer-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); grid-auto-rows: 1fr; gap: var(--space-3); }
.answer-card { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: var(--space-3); width: 100%; min-width: 0; min-height: 104px; padding: var(--space-4); border: 1.5px solid var(--control-line); border-radius: var(--radius); background: var(--surface); color: var(--ink); transition: opacity 120ms ease; }
.answer-card .diagram { width: 100%; max-width: 190px; min-height: 48px; }
.answer-card[aria-pressed="true"], .answer-card.is-selected { background: var(--wash); box-shadow: inset 0 0 0 1px var(--ink); }
.answer-label { display: flex; align-items: center; gap: var(--space-2); font-size: .82rem; font-weight: 600; }
.task-actions { display: flex; justify-content: space-between; flex-wrap: wrap; gap: var(--space-3); }

/* Feedback labels must name chosen/correct/invalid; these tones are not scores. */
.feedback { display: grid; gap: var(--space-5); }
.feedback-summary { display: flex; align-items: flex-start; gap: var(--space-3); }
.feedback-comparison { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-3); }
.feedback-card { display: grid; align-content: start; gap: var(--space-3); padding: var(--space-4); border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.feedback-card.is-correct { background: var(--wash); }
.feedback-explanation, .technical-notice { padding: var(--space-4); border-radius: var(--radius-sm); background: var(--soft); }
.assessment-acknowledgment { display: grid; justify-items: center; gap: var(--space-4); text-align: center; }
.report-summary, .report-families { display: grid; gap: var(--space-3); }
.report-card { display: grid; gap: var(--space-4); }
.metric-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--space-4); }
.metric { display: grid; gap: var(--space-1); }
.metric dt { color: var(--muted); font-size: .82rem; }
.metric dd { font-size: 1.5rem; font-weight: 600; font-variant-numeric: tabular-nums; letter-spacing: -.03em; }
.metric .insufficient-data { font-size: .88rem; font-weight: 400; letter-spacing: normal; }
.report-breakdown { display: grid; gap: var(--space-3); }
.report-breakdown > div { display: flex; justify-content: space-between; align-items: baseline; gap: var(--space-4); padding-bottom: var(--space-3); border-bottom: 1px solid var(--line); font-size: .88rem; }
.report-breakdown dd { font-variant-numeric: tabular-nums; font-weight: 600; }
.history-list { display: grid; gap: var(--space-3); padding: 0; margin: 0; list-style: none; }
.history-item { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: var(--space-3); }
.history-item-copy { display: grid; gap: var(--space-1); flex: 1 1 170px; }
.privacy-screen, .confirmation-screen { display: grid; gap: var(--space-5); }
.consent-field { display: flex; align-items: flex-start; gap: var(--space-3); padding: var(--space-3); min-height: 48px; cursor: pointer; }
.consent-field input { width: 24px; height: 24px; flex: 0 0 24px; margin: 2px 0 0; accent-color: var(--accent); }
.danger-zone { display: grid; gap: var(--space-4); padding-top: var(--space-5); border-top: 1px solid var(--line); }
.confirmation-dialog { width: min(440px, calc(100% - 32px)); max-height: calc(100dvh - var(--safe-top) - var(--safe-bottom) - 32px); padding: var(--space-6); border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--surface); color: var(--ink); box-shadow: var(--shadow); overflow-y: auto; }
.confirmation-dialog::backdrop { background: #10182080; }
.confirmation-dialog[open] { display: grid; gap: var(--space-5); }
.network-notice { background: var(--soft); }
.network-retry .button { width: 100%; }
.loading-state { display: flex; justify-content: center; align-items: center; gap: var(--space-3); padding: var(--space-6); color: var(--muted); }
.toast { position: fixed; z-index: 30; inset-inline: max(var(--space-5), var(--safe-left)) max(var(--space-5), var(--safe-right)); bottom: calc(var(--space-5) + var(--safe-bottom) + var(--tg-content-safe-area-inset-bottom, 0px)); width: fit-content; max-width: 560px; margin-inline: auto; padding: var(--space-4) var(--space-5); border: 1px solid var(--line); border-radius: var(--radius); background: var(--ink); color: var(--surface); box-shadow: var(--shadow); font-size: .88rem; overflow-wrap: anywhere; }
.toast:empty { display: none; }

@media (hover: hover) {
  .button:hover:not(:disabled), .answer-card:hover:not(:disabled), .family-tile:hover:not(:disabled) { box-shadow: inset 0 0 0 1px currentColor; }
  .language-switch button:hover:not(:disabled) { background: var(--surface); }
  a:hover { text-decoration-thickness: 2px; }
  summary:hover { color: var(--accent); }
}
@media (max-width: 389px) {
  .app-shell { padding-inline: max(var(--space-4), var(--safe-left)) max(var(--space-4), var(--safe-right)); }
  .app-header { gap: var(--space-2); }
  .brand { gap: var(--space-2); }
  .brand-mark { width: 24px; height: 24px; flex-basis: 24px; }
  .brand-copy { font-size: .72rem; }
  .brand-caption { font-size: .64rem; }
  .welcome-family { padding: var(--space-4); gap: var(--space-3); }
  .family-copy h2 { font-size: .94rem; }
  .family-copy p { font-size: .76rem; }
  .family-tile { gap: var(--space-3); padding: var(--space-4); }
}
@media (min-width: 600px) {
  .app-shell { padding-inline: max(var(--space-8), var(--safe-left)) max(var(--space-8), var(--safe-right)); }
  .screen { padding-block: var(--space-10); }
  .welcome-family { grid-template-columns: minmax(0, 1fr) 190px; padding: var(--space-6); }
  .family-copy h2 { font-size: 1.15rem; }
  .answer-card { min-height: 120px; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
}
@media (forced-colors: active) {
  .button, .answer-card, .family-tile, .language-switch { border-color: ButtonText; }
  .button:disabled, .answer-card:disabled { color: GrayText; border-color: GrayText; }
  .bit, .token { fill: Canvas; stroke: CanvasText; }
  .bit-on, .bit[data-value="1"] { fill: CanvasText; }
  .flow-line, .flow-arrow, .slot, .mask-mark { stroke: CanvasText; }
  .answer-card[aria-pressed="true"] { outline: 3px solid Highlight; }
}