/* ============================================================
   MathNova — mobile-first cosmic math game
   Design system: deep space gradient, glowing cards, big targets
   ============================================================ */

:root {
  --bg-0: #150b2e;
  --bg-1: #241347;
  --bg-2: #36195f;
  --surface: rgba(255, 255, 255, 0.06);
  --surface-strong: rgba(255, 255, 255, 0.11);
  --border: rgba(255, 255, 255, 0.14);
  --text: #f5f2ff;
  --text-dim: #b6aede;
  --primary-1: #7c5cff;
  --primary-2: #b845e8;
  --accent-1: #ffc93c;
  --accent-2: #ff8a5c;
  --good-1: #3ddc84;
  --good-2: #23b56d;
  --bad-1: #ff5d7e;
  --bad-2: #d8455f;
  --radius-l: 22px;
  --radius-m: 14px;
  --radius-s: 10px;
  --shadow-1: 0 6px 20px rgba(8, 4, 24, 0.35);
  --shadow-2: 0 10px 30px rgba(8, 4, 24, 0.45);
  --safe-top: env(safe-area-inset-top, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
  --font: "Fredoka", "Baloo 2", ui-rounded, system-ui, -apple-system, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }

/* Keep game visibility toggles authoritative over component display rules. */
[hidden] { display: none !important; }

html, body {
  margin: 0; padding: 0;
  height: 100%;
  font-family: var(--font);
  color: var(--text);
  background:
    radial-gradient(1200px 700px at 85% -10%, #4b2a86 0%, transparent 55%),
    radial-gradient(900px 600px at -10% 30%, #2d3f8f 0%, transparent 60%),
    linear-gradient(180deg, var(--bg-0) 0%, var(--bg-1) 60%, var(--bg-2) 100%);
  background-attachment: fixed;
  overscroll-behavior: none;
}

/* Twinkling starfield behind the app */
body::before {
  content: "";
  position: fixed; inset: 0;
  background-image:
    radial-gradient(2px 2px at 12% 22%, #fff 0%, transparent 100%),
    radial-gradient(1.6px 1.6px at 41% 8%, #cfe0ff 0%, transparent 100%),
    radial-gradient(2.2px 2.2px at 68% 34%, #fff 0%, transparent 100%),
    radial-gradient(1.4px 1.4px at 86% 12%, #ffe9c7 0%, transparent 100%),
    radial-gradient(2px 2px at 22% 66%, #e6d6ff 0%, transparent 100%),
    radial-gradient(1.8px 1.8px at 55% 80%, #fff 0%, transparent 100%),
    radial-gradient(1.4px 1.4px at 74% 92%, #cfe0ff 0%, transparent 100%);
  opacity: 0.5;
  pointer-events: none;
  z-index: 0;
}

#app {
  position: relative;
  z-index: 1;
  max-width: 560px;
  margin: 0 auto;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  padding: calc(var(--safe-top) + 8px) 16px calc(var(--safe-bottom) + 8px);
}

/* ---------------- App bar ---------------- */
#appbar {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 4px 12px;
}
#screen-title {
  flex: 1;
  font-size: 1.15rem;
  font-weight: 600;
  letter-spacing: 0.2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.icon-btn {
  width: 48px; height: 48px;
  flex: none;
  border: none;
  border-radius: 999px;
  background: var(--surface);
  color: var(--text);
  font-size: 1.35rem;
  line-height: 1;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.12s ease, background 0.12s ease;
}
.icon-btn:active { transform: scale(0.92); }

/* ---------------- Screens ---------------- */
#screens { position: relative; flex: 1; }
.screen {
  padding: 8px 0 24px;
  animation: screen-in 0.28s ease both;
}
@keyframes screen-in {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: none; }
}
body.motion-off .screen, body.motion-off .result-card, body.motion-off #toast { animation: none; }
.screen-sub {
  margin: 4px 0 14px;
  color: var(--text-dim);
  font-size: 0.98rem;
  line-height: 1.35;
}

/* ---------------- Hero (home) ---------------- */
.hero { text-align: center; padding: 18px 0 6px; }
.logo { width: 112px; height: 112px; filter: drop-shadow(0 8px 22px rgba(124, 92, 255, 0.45)); }
.app-title { margin: 6px 0 2px; font-size: 2rem; font-weight: 700; letter-spacing: 0.5px; }
.tagline { margin: 0; color: var(--text-dim); font-size: 1rem; }

/* ---------------- Stats strip ---------------- */
.stats-strip {
  display: flex;
  gap: 10px;
  margin: 16px 0 6px;
}
.stat {
  flex: 1;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-m);
  padding: 10px 8px 12px;
  text-align: center;
}
.stat-icon { font-size: 1.1rem; }
.stat-val { display: block; font-weight: 700; font-size: 1.25rem; }
.stat-label { color: var(--text-dim); font-size: 0.72rem; letter-spacing: 0.4px; text-transform: uppercase; }

/* ---------------- Buttons ---------------- */
.btn-primary, .btn-secondary, .btn-danger, .btn-big {
  border: none;
  border-radius: 999px;
  color: #fff;
  font-family: var(--font);
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.12s ease, filter 0.12s ease, box-shadow 0.12s ease;
  min-height: 52px;
  padding: 12px 22px;
  font-size: 1.05rem;
}
.btn-primary, .btn-big {
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2) 70%, #ff6f91);
  box-shadow: 0 8px 24px rgba(124, 92, 255, 0.45);
}
.btn-big {
  display: block;
  width: 100%;
  font-size: 1.5rem;
  letter-spacing: 2px;
  padding: 16px;
  text-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
}
.btn-secondary {
  background: var(--surface-strong);
  border: 1px solid var(--border);
}
.btn-danger {
  background: linear-gradient(135deg, var(--bad-1), var(--bad-2));
}
.btn-primary:active, .btn-big:active, .btn-secondary:active, .btn-danger:active {
  transform: scale(0.97);
  filter: brightness(1.08);
}
button:focus-visible, .toggle:focus-visible, .select:focus-visible {
  outline: 3px solid #ffd76a;
  outline-offset: 2px;
}
.link-btn {
  display: block;
  margin: 18px auto 0;
  background: none;
  border: none;
  color: var(--text-dim);
  font-family: var(--font);
  font-size: 0.95rem;
  text-decoration: underline dotted;
  cursor: pointer;
  min-height: 44px;
  padding: 10px;
}

/* ---------------- Mode grid (home) ---------------- */
.mode-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 18px;
}
.mode-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 2px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 14px 14px 16px;
  color: var(--text);
  font-family: var(--font);
  cursor: pointer;
  text-align: left;
  transition: transform 0.12s ease, background 0.12s ease;
  min-height: 118px;
}
.mode-card:active { transform: scale(0.97); }
.mode-emoji { font-size: 1.6rem; }
.mode-name { font-weight: 700; font-size: 1.02rem; }
.mode-desc { color: var(--text-dim); font-size: 0.8rem; line-height: 1.3; }

/* ---------------- Stage list ---------------- */
.stage-list { display: flex; flex-direction: column; gap: 12px; }
.stage-card {
  position: relative;
  display: block;
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 16px;
  font-family: var(--font);
  color: var(--text);
  cursor: pointer;
  text-align: left;
  background: linear-gradient(140deg, rgba(255,255,255,0.09), rgba(255,255,255,0.04));
  transition: transform 0.12s ease;
}
.stage-card:active { transform: scale(0.985); }
.stage-emoji { font-size: 2rem; }
.stage-name { font-weight: 700; font-size: 1.15rem; }
.stage-meta { color: var(--text-dim); font-size: 0.85rem; }
.stage-progress {
  height: 8px;
  border-radius: 99px;
  background: rgba(255, 255, 255, 0.12);
  margin-top: 12px;
  overflow: hidden;
}
.stage-progress-fill {
  height: 100%;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--accent-1), var(--accent-2));
  width: 0;
}
.stage-lock { position: absolute; top: 12px; right: 14px; font-size: 1.4rem; opacity: 0.75; }

/* ---------------- Topic list ---------------- */
.topic-list { display: flex; flex-direction: column; gap: 10px; }
.topic-chip {
  display: flex;
  align-items: center;
  gap: 12px;
  width: 100%;
  border: 1px solid var(--border);
  border-radius: var(--radius-m);
  background: var(--surface);
  padding: 12px 14px;
  color: var(--text);
  font-family: var(--font);
  cursor: pointer;
  transition: transform 0.12s ease;
}
.topic-chip:active { transform: scale(0.98); }
.topic-emoji { font-size: 1.5rem; flex: none; }
.topic-main { flex: 1; min-width: 0; }
.topic-name { font-weight: 600; font-size: 1rem; }
.topic-meta { color: var(--text-dim); font-size: 0.8rem; margin-top: 2px; }
.topic-stars { color: var(--accent-1); font-size: 0.95rem; letter-spacing: 1px; flex: none; }
.mastery-dot { width: 9px; height: 9px; border-radius: 99px; background: var(--good-1); margin-left: 6px; }

/* ---------------- Quiz ---------------- */
.quiz-head { margin-bottom: 10px; }
.quiz-topic { font-weight: 700; font-size: 1.05rem; }
.quiz-meters {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 8px;
  min-height: 22px;
}
.progress-bar {
  flex: 1;
  height: 10px;
  border-radius: 99px;
  background: rgba(255, 255, 255, 0.14);
  overflow: hidden;
}
.progress-fill {
  height: 100%;
  width: 0;
  border-radius: 99px;
  background: linear-gradient(90deg, var(--good-1), var(--primary-1));
  transition: width 0.25s ease;
}
.streak-flame { font-size: 0.95rem; color: var(--accent-2); flex: none; }
.rush-timer {
  font-variant-numeric: tabular-nums;
  font-weight: 700;
  color: var(--accent-1);
  flex: none;
}
.rush-timer.urgent { color: var(--bad-1); animation: pulse 0.5s ease infinite alternate; }
@keyframes pulse { from { transform: scale(1); } to { transform: scale(1.18); } }
body.motion-off .rush-timer.urgent { animation: none; }

.question-card {
  background: var(--surface-strong);
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 18px;
  box-shadow: var(--shadow-1);
}
.question-text {
  margin: 0;
  font-size: 1.6rem;
  font-weight: 600;
  line-height: 1.35;
  text-align: center;
  word-break: break-word;
}
.question-visual { margin-top: 12px; }
.question-visual svg { display: block; width: 100%; height: auto; }

.choices-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 16px;
}
.choice-btn {
  min-height: 74px;
  border: 2px solid var(--border);
  border-radius: var(--radius-m);
  background: var(--surface-strong);
  color: var(--text);
  font-family: var(--font);
  font-size: 1.45rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.1s ease, border-color 0.1s ease;
}
.choice-btn:active { transform: scale(0.96); }
.choice-btn.picked { border-color: var(--primary-1); }
.choice-btn.correct {
  border-color: var(--good-1);
  background: linear-gradient(135deg, rgba(61, 220, 132, 0.35), rgba(35, 181, 109, 0.28));
  animation: pop-good 0.35s ease;
}
.choice-btn.wrong {
  border-color: var(--bad-1);
  background: linear-gradient(135deg, rgba(255, 93, 126, 0.35), rgba(216, 69, 95, 0.28));
}
@keyframes pop-good { from { transform: scale(0.92); } to { transform: scale(1); } }
body.motion-off .choice-btn.correct { animation: none; }
body.motion-off .choice-btn.wrong { animation: none; }

/* Numpad */
.pad-display {
  margin-top: 16px;
  background: rgba(0, 0, 0, 0.35);
  border: 1px solid var(--border);
  border-radius: var(--radius-m);
  min-height: 64px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.9rem;
  font-weight: 600;
  letter-spacing: 2px;
  padding: 10px 14px;
  word-break: break-all;
}
.numpad {
  margin-top: 12px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}
.pad-btn {
  min-height: 62px;
  border: none;
  border-radius: var(--radius-m);
  background: var(--surface-strong);
  color: var(--text);
  font-family: var(--font);
  font-size: 1.35rem;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.08s ease, filter 0.08s ease;
}
.pad-btn:active { transform: scale(0.94); filter: brightness(1.2); }
.pad-btn.back { background: rgba(255, 93, 126, 0.28); }
.pad-btn.go { background: linear-gradient(135deg, var(--primary-1), var(--primary-2)); }
.pad-btn.blank { background: transparent; }
.pad-btn.zero { grid-column: span 1; }

/* Feedback */
.quiz-feedback {
  margin-top: 14px;
  border-radius: var(--radius-m);
  padding: 14px 16px;
  line-height: 1.45;
  font-size: 0.98rem;
  animation: screen-in 0.25s ease both;
}
.quiz-feedback.good {
  background: linear-gradient(135deg, rgba(61, 220, 132, 0.22), rgba(35, 181, 109, 0.14));
  border: 1px solid rgba(61, 220, 132, 0.5);
}
.quiz-feedback.bad {
  background: linear-gradient(135deg, rgba(255, 93, 126, 0.22), rgba(216, 69, 95, 0.14));
  border: 1px solid rgba(255, 93, 126, 0.5);
}
.fb-title { font-weight: 700; font-size: 1.1rem; margin: 0 0 6px; }
.fb-steps { margin: 0; padding-left: 1.4em; }
.fb-steps li { margin: 3px 0; color: var(--text); }
.fb-tip { color: var(--text-dim); font-size: 0.9rem; margin-top: 8px; }

.quiz-actions {
  display: flex;
  gap: 12px;
  margin-top: 16px;
}
.quiz-actions .btn-secondary { flex: 1; }
.quiz-actions .btn-primary { flex: 2; }

/* ---------------- Result ---------------- */
.result-card {
  background: var(--surface-strong);
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 26px 20px;
  text-align: center;
  box-shadow: var(--shadow-2);
  animation: result-in 0.35s ease both;
}
@keyframes result-in {
  from { opacity: 0; transform: scale(0.9); }
  to { opacity: 1; transform: none; }
}
body.motion-off .result-card { animation: none; }
.result-title { margin: 0 0 8px; font-size: 1.7rem; }
.result-stars { font-size: 2.6rem; letter-spacing: 4px; color: var(--accent-1); min-height: 42px; }
.result-stats { margin: 12px 0 18px; color: var(--text-dim); line-height: 1.7; }
.result-stats b { color: var(--text); }
.result-actions { display: flex; flex-direction: column; gap: 12px; }
.result-actions .btn-primary, .result-actions .btn-secondary { width: 100%; }

/* ---------------- Learn ---------------- */
.learn-detail { padding-top: 4px; }
.learn-title { margin: 0 0 10px; }
.learn-body { line-height: 1.55; color: var(--text); }
.learn-body p { margin: 8px 0; }
.learn-body .rule {
  background: var(--surface);
  border-left: 4px solid var(--accent-1);
  border-radius: var(--radius-s);
  padding: 10px 14px;
  margin: 10px 0;
  font-weight: 600;
}
.learn-example {
  margin-top: 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-m);
  padding: 14px 16px;
}
.learn-example-head { margin: 0 0 8px; font-weight: 700; color: var(--accent-1); }
.learn-example-steps { margin: 0; padding-left: 1.3em; line-height: 1.6; }
.learn-example-steps li { margin: 4px 0; }
.learn-example .question-visual { margin-top: 12px; }
#btn-learn-practice { width: 100%; margin-top: 18px; }

/* ---------------- Achievements ---------------- */
.ach-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 12px;
}
.ach-badge {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-m);
  padding: 14px 12px;
  text-align: center;
}
.ach-badge.locked { opacity: 0.45; filter: grayscale(0.7); }
.ach-emoji { font-size: 2rem; }
.ach-name { font-weight: 700; font-size: 0.92rem; margin-top: 4px; }
.ach-desc { color: var(--text-dim); font-size: 0.75rem; margin-top: 3px; line-height: 1.3; }

/* ---------------- Settings ---------------- */
.settings-group {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 16px;
  margin-bottom: 14px;
}
.settings-head { margin: 0 0 10px; font-size: 1.05rem; }
.setting-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  min-height: 48px;
  font-size: 0.98rem;
}
.setting-row-col { flex-direction: column; align-items: stretch; }
.setting-row .hint { color: var(--text-dim); font-size: 0.78rem; }
.toggle {
  width: 52px; height: 30px;
  appearance: none;
  border-radius: 99px;
  background: rgba(255, 255, 255, 0.18);
  position: relative;
  cursor: pointer;
  transition: background 0.15s ease;
  flex: none;
}
.toggle::after {
  content: "";
  position: absolute;
  top: 3px; left: 3px;
  width: 24px; height: 24px;
  border-radius: 99px;
  background: #fff;
  transition: transform 0.15s ease;
}
.toggle:checked { background: var(--good-1); }
.toggle:checked::after { transform: translateX(22px); }
.select {
  width: 100%;
  margin-top: 8px;
  padding: 12px;
  border-radius: var(--radius-m);
  background: rgba(0, 0, 0, 0.35);
  color: var(--text);
  border: 1px solid var(--border);
  font-family: var(--font);
  font-size: 0.95rem;
}
.settings-text { color: var(--text-dim); font-size: 0.88rem; line-height: 1.5; margin: 6px 0; }
.btn-danger { width: 100%; margin-top: 12px; }
.settings-group .btn-secondary { width: 100%; margin-top: 12px; }
.footer-note { text-align: center; color: var(--text-dim); font-size: 0.8rem; margin-top: 20px; }

/* AdSense placements stay in document flow, separated from game controls. */
.ad-slot { width: 100%; min-width: 0; min-height: 280px; margin: 150px auto; }
.ad-label { color: var(--text-dim); font: 12px var(--font); text-align: center; }
.ad-slot ins { width: 100%; min-height: 250px; }

/* ---------------- Toast ---------------- */
.toast {
  position: fixed;
  left: 50%;
  bottom: calc(var(--safe-bottom) + 72px);
  transform: translateX(-50%);
  z-index: 80;
  background: rgba(20, 12, 40, 0.95);
  border: 1px solid var(--accent-1);
  border-radius: 999px;
  padding: 12px 20px;
  font-size: 0.95rem;
  font-weight: 600;
  white-space: nowrap;
  animation: toast-in 0.3s ease both;
  max-width: 90vw;
  overflow: hidden;
  text-overflow: ellipsis;
}
@keyframes toast-in {
  from { opacity: 0; transform: translateX(-50%) translateY(14px); }
  to { opacity: 1; transform: translateX(-50%) translateY(0); }
}
body.motion-off .toast { animation: none; }

/* ---------------- Tablet / desktop polish ---------------- */
@media (min-width: 640px) {
  #app { padding-top: calc(var(--safe-top) + 16px); }
  .choices-grid { max-width: 420px; margin-left: auto; margin-right: auto; }
  .numpad { max-width: 420px; margin-left: auto; margin-right: auto; }
}

/* ---------------- Very small screens ---------------- */
@media (max-width: 360px) {
  .question-text { font-size: 1.35rem; }
  .choice-btn { font-size: 1.2rem; }
  .mode-grid { grid-template-columns: 1fr; }
}

/* ---------------- SVG teaching visuals ---------------- */
.dim { opacity: 0.35; }
.mn-svg { display: block; width: 100%; height: auto; }
.mn-svg text { fill: #f5f2ff; font-family: var(--font); }
.vg-star { fill: #ffd76a; }
.vg-star-blue { fill: #7cc5ff; }
.vg-star-green { fill: #7dff9e; }
.vg-gone { opacity: 0.38; }
.vg-x { stroke: #ff5d7e; stroke-width: 4; fill: none; }
.vg-line { stroke: #b6aede; stroke-width: 3; }
.vg-tick { stroke: #b6aede; stroke-width: 2; }
.vg-num { fill: #f5f2ff; font-size: 14px; font-family: var(--font); }
.vg-label { fill: #b6aede; font-size: 14px; font-family: var(--font); }
.vg-note { fill: #b6aede; font-size: 12px; font-family: var(--font); }
.vg-arc { stroke: #7c5cff; stroke-width: 3; fill: none; }
.vg-arc2 { stroke: #ff8a5c; stroke-width: 3; fill: none; }
.vg-ten-a { fill: #7cc5ff; }
.vg-ten-b { fill: #ff8a5c; }
.vg-dot { fill: #7c5cff; }
.vg-dot-dim { fill: #b6aede; opacity: 0.5; }
.vg-seg { fill: rgba(255, 255, 255, 0.08); stroke: #b6aede; stroke-width: 1.5; }
.vg-seg-filled { fill: #7c5cff; }
.vg-segline { stroke: #b6aede; stroke-width: 2; }
.vg-segframe { fill: none; stroke: #b6aede; stroke-width: 2.5; }
.vg-frac { fill: #ffd76a; font-size: 22px; font-family: var(--font); }

/* ---------------- Print / reduced-motion ---------------- */
@media (prefers-reduced-motion: reduce) {
  * { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

/* MathNova 2 · a calm observatory for curious minds */
:root {
  --bg-0: #0d1227; --bg-1: #141a36; --bg-2: #202344;
  --text: #f5f5ff; --text-dim: #bfc5df;
  --surface: rgba(177,191,255,.065); --border: rgba(174,189,242,.18);
  --primary-1: #8b79ff; --primary-2: #6654db;
  --font: "Fredoka", ui-rounded, system-ui, sans-serif;
}
html, body { background: radial-gradient(ellipse at 90% 10%, #332757 0, transparent 48%), radial-gradient(ellipse at 0% 65%, #142f43 0, transparent 48%), #0d1227; background-attachment: fixed; }
body { font-family: system-ui, -apple-system, "Segoe UI", sans-serif; line-height: 1.55; }
body::before { opacity: .25; }
#app { max-width: 1140px; padding: 12px 32px 24px; }
#appbar { padding: 8px 0 20px; border-bottom: 1px solid var(--border); margin-bottom: 16px; }
#screen-title { font-family: var(--font); font-size: 1.4rem; letter-spacing: -.02em; }
#screen-title:focus { outline: none; }
h2, h3 { font-family: var(--font); letter-spacing: -.025em; line-height: 1.2; }
h2 { font-size: clamp(1.8rem, 3vw, 2.5rem); }
h3 { font-weight: 500; font-size: 1.3rem; }
button, input, select { font: inherit; }
button { touch-action: manipulation; }
a { color: #bbceff; text-underline-offset: 3px; }
button:focus-visible, a:focus-visible, input:focus-visible, select:focus-visible, summary:focus-visible { outline: 3px solid #8befde; outline-offset: 4px; }
button:disabled { cursor: default; }
button:not(:disabled) { transition: transform .15s ease, border-color .15s ease, background .15s ease; }
button:not(:disabled):hover { border-color: #9388e4; }
.btn-primary, .btn-secondary, .btn-danger { font-family: var(--font); font-weight: 500; min-height: 50px; padding: 12px 24px; line-height: 1.25; }
.btn-primary { color: #fff; background: linear-gradient(120deg, #7665de, #6351cd); box-shadow: 0 8px 26px rgba(102,80,211,.18); border: 1px solid #aa9bff; }
.btn-secondary { background: #252d4a; border: 1px solid #626d92; }
.hero { display: grid; grid-template-columns: 1.5fr 1fr; gap: 28px; align-items: center; text-align: left; padding: 28px 0 32px; }
.eyebrow { font-size: .68rem; font-weight: 700; letter-spacing: .16em; color: #91dccf; margin: 0 0 14px; }
.app-title { font-size: clamp(2.35rem, 4.7vw, 3.8rem); font-weight: 500; line-height: 1.08; margin: 0 0 20px; letter-spacing: -.04em; }
.app-title span { color: #c8b4ff; }
.tagline { font-size: 1rem; line-height: 1.7; max-width: 510px; margin: 0; color: var(--text-dim); }
.hero-orbit { position: relative; width: 240px; height: 240px; margin: auto; display: grid; place-items: center; border-radius: 50%; border: 1px solid rgba(181,162,240,.26); background: radial-gradient(circle, rgba(137,118,249,.17), transparent 65%); }
.hero-orbit::before { content: ""; position: absolute; inset: 25px -20px; border: 1px solid rgba(142,227,213,.4); border-radius: 50%; transform: rotate(-32deg); }
.logo { width: 165px; height: 165px; transform: rotate(-12deg); filter: drop-shadow(0 0 30px #6554a666); }
.orbit-dot { position: absolute; width: 19px; height: 19px; background: #8de5d4; border-radius: 50%; right: 18px; top: 38px; box-shadow: 0 0 35px #8de5d444; }
.orbit-caption { position: absolute; font-size: .58rem; letter-spacing: .2em; color: #ada3cf; bottom: -20px; }
.path-picker { display: flex; align-items: center; gap: 16px; padding: 16px 0; }
.path-picker label { font-weight: 650; font-size: .85rem; }
.path-picker .select { max-width: 325px; min-height: 46px; border-radius: 12px; background: #202842; color: #fff; }
.path-note { color: var(--text-dim); font-size: .76rem; margin-left: auto; }
.mission-card { border: 1px solid #6a648e; border-radius: 20px; background: linear-gradient(110deg, #303354, #302740); display: flex; gap: 28px; align-items: center; justify-content: space-between; padding: 26px 28px; }
.mission-card .eyebrow { color: #dccdff; margin-bottom: 8px; }
.mission-card h3 { font-size: 1.7rem; margin: 0 0 8px; }
.mission-card p:not(.eyebrow) { color: #c8c8df; font-size: .88rem; margin: 0; }
.mission-card .btn-big { flex: none; width: auto; min-width: 188px; margin: 0; font-size: 1.1rem; }
.mission-card .btn-big span { margin-left: 16px; }
.stats-strip { background: transparent; border: 0; padding: 22px 0; margin: 0; justify-content: flex-start; gap: 38px; }
.stat { display: flex; flex-direction: row; gap: 8px; align-items: baseline; }
.stat-val { font: 1.15rem var(--font); }
.stat-label { font-size: .75rem; }
.stat-icon { font-size: 1rem; }
.section-heading { margin: 18px 0 16px; display: flex; align-items: baseline; justify-content: space-between; gap: 16px; }
.section-heading h3 { margin: 0; }
.section-heading span { color: var(--text-dim); font-size: .75rem; }
.mode-grid { grid-template-columns: repeat(3, 1fr); gap: 14px; margin: 0 0 18px; }
.mode-card { min-height: 164px; padding: 20px; border-radius: 16px; background: linear-gradient(150deg, #202842, #171e35); gap: 7px; }
.mode-card:hover { transform: translateY(-3px); background: #282d49; }
.mode-emoji { color: #bdb0ff; font: 1.75rem var(--font); margin-bottom: 3px; }
.mode-name { font: 1.12rem var(--font); }
.mode-desc { font-size: .79rem; line-height: 1.6; }
.grade-list { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin: 26px 0; }
.grade-card { display: flex; flex-direction: column; text-align: left; color: var(--text); padding: 22px; border: 1px solid var(--border); border-radius: 18px; background: linear-gradient(145deg, #252c47, #1b2238); min-height: 215px; }
.grade-card:nth-child(3n+2) { background: linear-gradient(145deg, #283446, #1a2737); }
.grade-card:nth-child(3n+3) { background: linear-gradient(145deg, #332c48, #221e36); }
.grade-card.current { border-color: #afa1ff; box-shadow: inset 0 0 0 1px #afa1ff; }
.grade-label { color: #bcb3ed; text-transform: uppercase; letter-spacing: .12em; font-size: .7rem; font-weight: 700; margin-bottom: 12px; }
.grade-world { font: 1.4rem var(--font); line-height: 1.2; margin-bottom: 10px; }
.grade-description { font-size: .82rem; color: var(--text-dim); line-height: 1.5; }
.grade-foot { color: #9ed9d4; display: flex; justify-content: space-between; gap: 12px; font-size: .73rem; padding-top: 22px; margin-top: auto; width: 100%; }
.legacy-paths { margin: 30px 0; }
.legacy-paths summary { min-height: 48px; color: var(--text-dim); cursor: pointer; }
.topic-main { display: flex; flex-direction: column; text-align: left; gap: 5px; }
.topic-chip { padding: 19px 22px; background: #202841; border-radius: 14px; }
.topic-name { font: 1.13rem var(--font); }
.topic-stars { font-size: .9rem; white-space: nowrap; }
.topic-emoji { color: #b9acf7; }
#screen-topics, #screen-learn-detail, #screen-review, #screen-progress, #screen-settings, #screen-lab { max-width: 780px; margin-inline: auto; }
#screen-quiz, #screen-result { max-width: 660px; margin: 20px auto 0; }
.quiz-head { margin: 0 0 18px; }
.quiz-topic { font: 1.05rem var(--font); }
.quiz-count { float: right; font-size: .85rem; color: var(--text-dim); }
.quiz-meters { margin-top: 14px; }
.question-card { background: linear-gradient(145deg, #282d4f, #242942); border: 1px solid #636889; padding: 28px; border-radius: 20px; }
.question-text { font: 500 clamp(1.35rem, 3vw, 1.9rem)/1.45 var(--font); margin: 0; }
.question-text:focus { outline: none; }
.question-visual:empty { display: none; }
.choices-grid { margin-top: 22px; gap: 12px; }
.choice-btn { min-height: 74px; background: #242c49; border: 1px solid #72789a; font-family: var(--font); font-weight: 500; font-size: 1.55rem; border-radius: 14px; }
.choice-btn.correct { border-color: #8befbb; background: #194c40; color: #ddfff0; }
.choice-btn.wrong { border-color: #ffa4ba; background: #5a293f; color: #ffe5ed; }
.quiz-actions { display: flex; gap: 12px; margin-top: 14px; }
.quiz-actions { flex-wrap: wrap; }
.quiz-actions button { flex: 1; }
.quiz-status { color: #d5e9e1; font-size: .88rem; margin: 14px 0 0; }
.quiz-status:empty { margin: 0; }
.quiz-feedback { background: #242b44; font-size: .92rem; }
.quiz-feedback.good { border-color: #568d78; }
.quiz-feedback.bad { border-color: #aa728c; }
.fb-title { font: 1.1rem var(--font); }
.keyboard-help { text-align: center; color: #adb6d6; font-size: .72rem; margin-top: 22px; }
.read-btn { min-height: 44px; border: 1px solid #6e8995; border-radius: 12px; background: #203944; color: #d6fff1; padding: 10px 14px; font-size: .88rem; line-height: 1.3; cursor: pointer; }
.read-btn[aria-pressed="true"] { background: #35605f; border-color: #9ce8d6; }
.question-card > .read-btn { margin-bottom: 12px; }
.read-status { font-size: .8rem; color: #c4dfed; margin: 10px 0 16px; }
.read-status:empty { display: none; }
.learn-detail > .read-btn, .lab-workbench > .read-btn { margin-bottom: 16px; }
.example-prompt { font-family: var(--font); font-size: 1.3rem; }
#learn-example-steps { padding-left: 24px; }
#learn-example-steps li { padding: 4px 0; }
.report-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin: 28px 0; }
.report-stat { padding: 24px 16px; border: 1px solid var(--border); border-radius: 16px; background: var(--surface); }
.report-stat strong { display: block; font: 2rem var(--font); color: #bfb1ff; }
.report-stat span { color: var(--text-dim); font-size: .8rem; }
.history-row { border-bottom: 1px solid var(--border); padding: 14px 0; color: var(--text-dim); font-size: .85rem; }
.empty-state { padding: 35px; border: 1px dashed #717c9f; border-radius: 18px; background: var(--surface); color: #d1d9ed; }
#btn-review-start { width: 100%; margin-top: 24px; }
.site-footer { border-top: 1px solid var(--border); padding-top: 18px; display: flex; justify-content: space-between; align-items: center; gap: 12px; color: #a9b1cf; font-size: .72rem; }
.site-footer .link-btn { font-size: .75rem; margin: 0; min-height: 44px; }
#screen-settings .select { background: #222a43; }
.lab-invitation { display: flex; width: 100%; align-items: center; gap: 20px; padding: 22px 26px; border: 1px solid #657e8c; border-radius: 18px; background: linear-gradient(105deg, #173b43, #242d48); color: #e1fbf3; text-align: left; }
.lab-invitation > span:first-child { font-size: 2rem; color: #9ce8d6; }
.lab-invitation > span:nth-child(2) { flex: 1; }
.lab-invitation strong { display: block; font: 1.3rem var(--font); }
.lab-invitation span span { display: block; font-size: .85rem; color: #c0ddd9; margin-top: 4px; }
.lab-stations { display: flex; flex-wrap: wrap; gap: 8px; margin: 26px 0 18px; }
.lab-stations button { flex: 1; padding: 12px 14px; }
.lab-stations [aria-pressed="true"] { background: #354f54; border-color: #9ce8d6; color: #d9fff4; box-shadow: inset 0 -3px #9ce8d6; }
.lab-workbench { padding: clamp(16px, 4vw, 30px); border: 1px solid var(--border); border-radius: 20px; background: var(--surface); }
.lab-workbench h3 { margin-top: 0; font-size: 1.6rem; }
.lab-controls { display: flex; flex-wrap: wrap; gap: 10px; margin: 20px 0; }
.lab-controls button { flex: 1; padding-inline: 15px; }
.ten-frame { display: grid; grid-template-columns: repeat(5, minmax(44px, 1fr)); gap: 6px; max-width: 430px; margin: 14px auto; padding: 0; }
.ten-frame.bundled-ten { outline: 4px solid #5e9f88; outline-offset: 5px; border-radius: 8px; background: #5e9f88; }
.lab-group-summary { max-width: 430px; margin: 20px auto; padding: 14px; border: 2px solid #5e9f88; border-radius: 12px; font-weight: 600; }
.question-text { scroll-margin-top: 100px; }
.counter-slot { height: 54px; min-width: 44px; display: grid; place-items: center; border: 1px solid #7c8ba5; background: #19283b; border-radius: 8px; padding: 0; }
.counter-slot span { height: 28px; width: 28px; border: 1px dashed #8796ad; border-radius: 50%; }
.counter-slot[aria-pressed="true"] span { border: 1px solid #c8fff3; background: #8fdec9; box-shadow: inset -5px -5px #5bbda6; }
#lab-frame-second .counter-slot[aria-pressed="true"] span { border-color: #efdaff; background: #c9adfa; box-shadow: inset -5px -5px #9d7cde; }
.lab-select-label { display: block; font-weight: 600; margin: 22px 0 10px; }
#lab-denominator { background: #25314a; min-height: 48px; width: 100%; }
.lab-caption { font-size: .8rem; color: var(--text-dim); margin-bottom: 9px; }
.fraction-tank { display: grid; height: 76px; gap: 2px; padding: 3px; border: 2px solid #a3c8bf; border-radius: 8px; }
.fraction-tank span { background: #23303f; border: 1px solid #667e7e; }
.fraction-tank .filled { background: #8fdec9; }
.fraction-tank.equivalent { border-color: #c7b5ec; }
.fraction-tank.equivalent .filled { background: #c9adfa; }
.lab-readout { padding: 18px 14px; border: 1px solid #657887; border-radius: 12px; background: #192d3c; font-family: var(--font); font-size: clamp(1.1rem, 3vw, 1.5rem); text-align: center; color: #d9fff4; }
.lab-number-line { margin: 26px auto 10px; max-width: 600px; }
.lab-number-line svg { display: block; width: 100%; overflow: visible; }
.lab-axis { stroke: #9daac4; stroke-width: 2; }
.lab-tick { fill: #c3cee6; text-anchor: middle; font: 20px system-ui; }
.lab-travel { stroke: #8fdec9; stroke-width: 5; }
.lab-start { fill: #e8bcff; }
.lab-position { fill: #8fdec9; stroke: #ecfff9; stroke-width: 2; }
.lab-position-label { fill: #e4fff6; text-anchor: middle; font: 28px system-ui; }
.lab-challenge { border-top: 1px solid var(--border); padding-top: 24px; margin-top: 26px; }
.lab-challenge .eyebrow { margin-bottom: 8px; }
.lab-active-goal { color: #e4fff5; background: #21414a; border-left: 3px solid #9ce8d6; border-radius: 0 10px 10px 0; padding: 16px; margin: 20px 0; }
#lab-feedback:empty { display: none; }
#lab-feedback { color: #e5d9ff; margin-bottom: 0; }
#lab-feedback.lab-success { color: #a7f1d9; }
#btn-learn-lab { margin-top: 14px; width: 100%; }
@media (max-width: 440px) {
  .lab-workbench { padding-inline: 16px; }
  .lab-stations { gap: 6px; }
  .lab-stations button { padding-inline: 10px; font-size: .88rem; }
  .lab-invitation { padding: 20px 16px; gap: 14px; }
  .counter-slot { height: 48px; }
  .lab-controls button { flex-basis: 100%; }
}
@media (min-width: 900px) {
  #learn-list { display: grid; grid-template-columns: 1fr 1fr; }
  #learn-list > .screen-sub { grid-column: 1 / -1; margin: 22px 0 5px; }
}
@media (max-width: 720px) {
  #app { padding: 10px 20px 22px; }
  .hero { grid-template-columns: 1fr 130px; gap: 10px; padding-top: 20px; }
  .hero-orbit { width: 115px; height: 115px; }
  .hero-orbit::before { inset: 10px -10px; }
  .logo { width: 95px; height: 95px; }
  .orbit-dot { height: 12px; width: 12px; right: 5px; top: 12px; }
  .orbit-caption { display: none; }
  .app-title { font-size: 2.25rem; }
  .tagline { font-size: .88rem; }
  .path-picker { flex-wrap: wrap; gap: 8px; }
  .path-picker .select { max-width: none; flex: 1; min-width: 220px; }
  .path-note { width: 100%; margin: 0; }
  .mission-card { padding: 22px; gap: 20px; flex-wrap: wrap; }
  .mission-card .btn-big { width: 100%; }
  .mission-card h3 { font-size: 1.55rem; }
  .mode-grid { grid-template-columns: 1fr 1fr; }
  .grade-list { grid-template-columns: 1fr 1fr; }
  .section-heading span { display: none; }
  .stats-strip { gap: 18px; justify-content: space-between; }
  .stat { gap: 5px; }
  .stat-label { font-size: .66rem; }
  .site-footer { flex-direction: column; gap: 0; }
}
@media (max-width: 440px) {
  #app { padding-inline: 16px; }
  .hero { grid-template-columns: 1fr; }
  .hero-orbit { display: none; }
  .app-title { font-size: 2.6rem; }
  .hero .eyebrow { font-size: .61rem; }
  .mode-card { padding: 17px; min-height: 165px; }
  .grade-list { gap: 10px; }
  .grade-card { padding: 18px 14px; min-height: 230px; }
  .grade-world { font-size: 1.22rem; }
  .topic-chip { padding: 16px 14px; gap: 10px; }
  .topic-stars { font-size: .65rem; letter-spacing: 0; }
  .question-card { padding: 22px 17px; }
  .report-stat { padding: 18px 10px; }
  .report-stat strong { font-size: 1.6rem; }
  .report-stat span { font-size: .7rem; }
}

/* Sound desk and starlight atmosphere */
.audio-toggle { color: #c7bbef; }
.audio-toggle .sound-slash, .audio-toggle.is-muted .sound-waves { display: none; }
.audio-toggle.is-muted .sound-slash { display: block; }
.audio-toggle.is-muted { background: #372a48; color: #ffd0d9; }
.atmosphere-settings { background: linear-gradient(135deg, #242a48, #24223e); }
.soundtrack-card { display: flex; align-items: center; gap: 14px; padding: 16px; margin: 18px 0 8px; background: #11192e; border: 1px solid #474762; border-radius: 16px; }
.track-art { display: grid; place-items: center; flex: none; width: 54px; height: 54px; font-size: 2rem; color: #e2d4ff; background: radial-gradient(circle, #65548e, #263756); border: 1px solid #8b7aa7; border-radius: 50%; box-shadow: 0 0 22px #b294e91a; }
.track-description { display: block; margin-top: 3px; color: #bcb7d3; font-size: .8rem; }
.track-badge { margin-left: auto; color: #a8e4d5; font-size: .58rem; letter-spacing: .1em; }
.audio-status { min-height: 1.6em; }
.sound-controls { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; margin: 4px 0 18px; }
.sound-channel { min-width: 0; border-top: 1px solid #46465e; padding-top: 12px; }
.volume-label { display: flex; align-items: center; justify-content: space-between; gap: 12px; font-size: .85rem; color: #d4cfe5; margin-top: 10px; }
.volume-label output { font-variant-numeric: tabular-nums; color: #a8e4d5; font-size: .78rem; }
.volume-slider { display: block; width: 100%; min-width: 0; height: 44px; margin: 0; padding: 0; accent-color: #a6e7d8; cursor: pointer; background: transparent; }
.volume-slider:focus-visible { outline: 3px solid #d4bfff; outline-offset: 3px; border-radius: 8px; }
.atmosphere-settings > .setting-row { border-top: 1px solid #46465e; padding: 12px 0; margin-top: 12px; }
.setting-detail { display: block; color: #bcb7d3; font-size: .76rem; font-weight: 400; }
#vfx-canvas { position: fixed; inset: 0; width: 100%; height: 100%; pointer-events: none; z-index: 35; }
.vfx-success { animation: starlight-reward .7s ease-out both !important; }
.vfx-hint { animation: starlight-hint .65s ease-out both !important; }
.vfx-complete { animation: starlight-complete 1.4s ease-out both !important; }
@keyframes starlight-reward {
  0% { box-shadow: 0 0 0 0 #98f0d260; }
  30% { box-shadow: 0 0 0 7px #98f0d218, 0 0 32px #98f0d244; }
  100% { box-shadow: 0 0 0 15px #98f0d200; }
}
@keyframes starlight-hint {
  0%, 100% { box-shadow: 0 0 0 0 #b0dcff00; }
  40% { box-shadow: 0 0 0 5px #b0dcff22; }
}
@keyframes starlight-complete {
  0% { transform: scale(.94); text-shadow: 0 0 0 #ffe6a300; }
  35% { transform: scale(1.06); text-shadow: 0 0 30px #ffe6a388; }
  100% { transform: scale(1); text-shadow: 0 0 12px #ffe6a322; }
}
.hero-orbit::before { animation: observatory-orbit 28s linear infinite; }
.hero-orbit::after { content: ''; position: absolute; inset: -10px 20px; border: 1px solid #bfa7ff26; border-radius: 50%; transform: rotate(28deg); }
.orbit-dot { animation: observatory-breathe 5s ease-in-out infinite; }
@keyframes observatory-orbit { to { transform: rotate(328deg); } }
@keyframes observatory-breathe { 50% { box-shadow: 0 0 34px #8de5d46b; } }
/* Calm corrective feedback, without shaking the learner's answer. */
.choice-btn.wrong { animation: starlight-hint .65s ease-out; }
body.vfx-off .hero-orbit::before, body.vfx-off .orbit-dot,
body.vfx-off .choice-btn.correct, body.vfx-off .choice-btn.wrong,
body.motion-off .hero-orbit::before, body.motion-off .orbit-dot,
body.motion-off .vfx-success, body.motion-off .vfx-hint, body.motion-off .vfx-complete { animation: none !important; }
body.vfx-off #vfx-canvas, body.motion-off #vfx-canvas { display: none; }
@media (prefers-reduced-motion: reduce) {
  #vfx-canvas { display: none; }
  .hero-orbit::before, .orbit-dot, .vfx-success, .vfx-hint, .vfx-complete { animation: none !important; }
}
@media (max-width: 580px) {
  .sound-controls { grid-template-columns: 1fr; gap: 12px; }
  .track-badge { display: none; }
  .soundtrack-card { padding: 12px; gap: 10px; }
}

/* Language controls and bidirectional layouts */
.language-bar { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 6px 20px; margin: -4px 0 22px; }
.language-control { display: flex; align-items: center; gap: 12px; color: #d4cfe5; font-size: .82rem; max-width: 100%; }
.language-control .select { width: auto; min-width: 160px; max-width: 100%; min-height: 44px; padding: 8px 30px 8px 12px; font: inherit; background-color: #1c233a; }
.language-status { margin: 0; color: #bcb7d3; font-size: .72rem; line-height: 1.5; }
.language-status:empty { display: none; }
[dir="rtl"] .language-control .select { padding: 8px 12px 8px 30px; }
[dir="rtl"] .topic-main, [dir="rtl"] .hero-copy, [dir="rtl"] .grade-card, [dir="rtl"] .quiz-feedback, [dir="rtl"] .learn-body, [dir="rtl"] .learn-example { text-align: start; }
[dir="rtl"] .track-badge { margin-left: 0; margin-right: auto; }
[dir="rtl"] #btn-back { transform: scaleX(-1); }
[dir="rtl"] .fb-steps, [dir="rtl"] .learn-example-steps { padding-left: 0; padding-right: 1.3em; }
#quiz-pad, #quiz-input, .mn-svg, #lab-line, .ten-frame, .fraction-tank { direction: ltr; unicode-bidi: isolate; }
.choice-btn { unicode-bidi: plaintext; }
[lang] .app-title, [lang] .mission-title, [lang] .btn-primary, [lang] .btn-secondary, [lang] .topic-name { overflow-wrap: anywhere; }
@media (max-width: 420px) {
  .language-control { width: 100%; justify-content: space-between; }
  .language-control .select { min-width: 0; max-width: 72%; }
}