/* ============================================================
   Project Enlight — main.css  (single source of truth)
   All chapter pages link to this file. Do NOT duplicate styles.
   ============================================================ */

/* ─── Design Tokens ─── */
:root {
  --bg: #F8F4EE;
  --surface: #ffffff;
  --surface2: #f5f0e8;
  --border: #e8e0d0;
  --text: #1a1a1a;
  --muted: #6b6260;
  --muted2: #A8A29E;

  /* Brand palette */
  --brand-cream: #F8F4EE;
  --brand-gold: #C9A84C;
  --brand-black: #000000;
  --brand-gray: #A8A29E;

  /* Accents */
  --accent: #C9A84C;
  --accent-dark: #9b7d2e;
  --accent2: #c0602a;
  --accent3: #059669;
  --accent4: #7c3aed;
  --accent5: #d97706;

  /* Difficulty colors */
  --easy: #dcfce7;    --easy-text: #166534;
  --med: #fef9c3;     --med-text: #854d0e;
  --hard: #fee2e2;    --hard-text: #991b1b;
}

/* ─── Reset ─── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: 'DM Sans', sans-serif;
  font-size: 1rem;
  min-height: 100vh;
  overflow-x: hidden;
}

/* ─── KaTeX ─── */
.katex { color: var(--accent) !important; font-size: 1.05em !important; }
.katex-display { color: var(--accent); margin: .4rem 0; }
.identity-formula .katex { font-size: 1.15em !important; }
.exact-table .katex { color: var(--text) !important; font-size: .92em !important; }
.ans-box .katex { color: var(--accent3) !important; }

/* ════════════════════════════════════════════
   TOPBAR & NAVIGATION
   ════════════════════════════════════════════ */
.topbar {
  background: var(--brand-cream);
  border-bottom: 1px solid var(--border);
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 100;
  gap: .5rem;
}

.logo {
  font-family: 'Cormorant Garamond', serif;
  font-size: 1.5rem;
  font-weight: 500;
  color: var(--brand-black);
  padding: 1rem 0;
  display: flex;
  align-items: center;
  gap: .6rem;
  white-space: nowrap;
}
.logo-badge {
  font-family: 'DM Mono', monospace;
  font-size: .6rem;
  background: var(--brand-gold);
  color: #fff;
  padding: 2px 7px;
  border-radius: 20px;
  letter-spacing: .05em;
}

.back-link {
  font-family: 'DM Mono', monospace;
  font-size: .72rem;
  color: var(--muted);
  text-decoration: none;
  padding: 0 .8rem;
  height: 64px;
  display: flex;
  align-items: center;
  border-right: 1px solid var(--border);
  margin-right: .5rem;
  flex-shrink: 0;
  transition: color .15s;
}
.back-link:hover { color: var(--brand-black); }

/* Chapter tab nav */
.nav { display: flex; overflow-x: auto; }
.nav-btn {
  background: none;
  border: none;
  cursor: pointer;
  font-family: 'DM Sans', sans-serif;
  font-size: .82rem;
  color: var(--muted);
  padding: 0 1rem;
  height: 64px;
  border-bottom: 2px solid transparent;
  transition: all .15s;
  white-space: nowrap;
}
.nav-btn:hover { color: var(--brand-black); }
.nav-btn.active { color: var(--brand-gold); border-bottom-color: var(--brand-gold); font-weight: 500; }

/* Subject switcher pill (Add Maths / Maths) */
.subject-switcher {
  display: flex;
  align-items: center;
  gap: .3rem;
  flex-shrink: 0;
  padding-right: .5rem;
  border-right: 1px solid var(--border);
  margin-right: .5rem;
}
.subj-pill {
  font-family: 'DM Mono', monospace;
  font-size: .63rem;
  letter-spacing: .06em;
  color: var(--muted);
  text-decoration: none;
  padding: 3px 10px;
  border-radius: 20px;
  border: 1px solid var(--border);
  transition: all .15s;
}
.subj-pill:hover { border-color: var(--brand-gold); color: var(--brand-black); }
.subj-pill.active { background: var(--brand-gold); color: #fff; border-color: var(--brand-gold); }

/* ─── QOL Toolbar ─── */
.qol-bar {
  display: flex;
  align-items: center;
  gap: .5rem;
  padding-left: 1rem;
  border-left: 1px solid var(--border);
  margin-left: .5rem;
  flex-shrink: 0;
}
.qol-btn {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--muted);
  font-size: .78rem;
  padding: 4px 10px;
  cursor: pointer;
  font-family: 'DM Mono', monospace;
  transition: all .15s;
  white-space: nowrap;
}
.qol-btn:hover { border-color: var(--brand-gold); color: var(--brand-black); }

/* ════════════════════════════════════════════
   MAIN CONTENT AREA
   ════════════════════════════════════════════ */
.main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2.5rem 2rem;
}
.tab-content { display: none; }
.tab-content.active { display: block; }

/* Section headings */
.section-title {
  font-family: 'Cormorant Garamond', serif;
  font-size: 2.2rem;
  font-weight: 500;
  margin-bottom: .4rem;
  letter-spacing: -.01em;
}
.section-sub { color: var(--muted); font-size: .9rem; margin-bottom: 2rem; }

/* ════════════════════════════════════════════
   NOTE CARD SYSTEM  (standardized)
   ════════════════════════════════════════════ */
.card {
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.4rem;
  margin-bottom: 1rem;
}

/* note-card — the premium padded card with olive-green left accent */
.note-card {
  background: #ffffff;
  border: 1px solid var(--border);
  border-left: 3px solid #5a7a3a;
  border-radius: 10px;
  padding: 1.4rem 1.6rem;
  margin-bottom: 1rem;
  box-shadow: 0 2px 8px rgba(0,0,0,.04);
}

/* label inside card */
.lbl {
  font-family: 'DM Mono', monospace;
  font-size: .68rem;
  letter-spacing: .1em;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: .7rem;
}

/* Grid helpers */
.grid { display: grid; gap: 1rem; }
.c2 { grid-template-columns: 1fr 1fr; }
.c3 { grid-template-columns: repeat(3, 1fr); }

/* ─── Info boxes ─── */
.warn-box {
  background: #fef2f2;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: .9rem 1rem;
  font-size: .85rem;
  color: var(--muted);
  line-height: 1.7;
  margin-top: .6rem;
}
.warn-box b { color: var(--accent2); }

.tip-box {
  background: #f0fdf4;
  border: 1px solid var(--accent3);
  border-radius: 8px;
  padding: .9rem 1rem;
  font-size: .85rem;
  color: var(--muted);
  line-height: 1.7;
  margin-top: .6rem;
}
.tip-box b { color: var(--accent3); }

.err-box {
  background: #fef2f2;
  border: 1px solid #fecaca;
  border-radius: 8px;
  padding: .9rem 1rem;
  font-size: .85rem;
  color: var(--muted);
  line-height: 1.7;
  margin-top: .6rem;
}
.err-box b { color: var(--accent2); }

/* ─── Solve card ─── */
.solve-card {
  background: #fff;
  border: 1px solid var(--border);
  border-left: 4px solid var(--accent);
  border-radius: 10px;
  padding: 1.5rem;
  margin-bottom: 1rem;
}
.solve-title { font-weight: 500; font-size: .95rem; margin-bottom: 1rem; color: var(--accent); }
.solve-step { display: flex; gap: .8rem; margin-bottom: .7rem; align-items: flex-start; }
.solve-num {
  font-family: 'DM Mono', monospace;
  font-size: .7rem;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 2px 6px;
  flex-shrink: 0;
  color: var(--muted);
  margin-top: 3px;
  min-width: 28px;
  text-align: center;
}
.solve-text { font-size: .9rem; line-height: 1.9; }

/* ─── Step list ─── */
.step-list { list-style: none; counter-reset: s; }
.step-list li {
  counter-increment: s;
  display: flex;
  gap: 1rem;
  align-items: flex-start;
  margin-bottom: .9rem;
}
.step-list li::before {
  content: counter(s);
  font-family: 'DM Mono', monospace;
  font-size: .7rem;
  background: var(--brand-gold);
  color: #fff;
  border-radius: 50%;
  width: 20px; height: 20px;
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0; margin-top: 3px;
}
.step-text { font-size: .9rem; line-height: 1.8; }

/* ─── Formula block ─── */
.formula-block {
  background: var(--surface2);
  border-left: 3px solid var(--accent);
  border-radius: 0 8px 8px 0;
  padding: .9rem 1.1rem;
  margin: .6rem 0;
  line-height: 2.8;
  text-align: center;
}

/* ─── Concept card (small centered box) ─── */
.concept-card {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.6rem;
  text-align: center;
}
.concept-title {
  font-family: 'DM Mono', monospace;
  font-size: .72rem;
  letter-spacing: .1em;
  color: var(--accent);
  text-transform: uppercase;
  margin-bottom: .6rem;
}
.concept-formula { font-size: 1rem; line-height: 2.5; margin-bottom: .5rem; }
.concept-desc { font-size: .83rem; color: var(--muted); line-height: 1.6; }

/* ─── Fn card (trig page) ─── */
.fn-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.2rem;
  text-align: center;
}
.fn-name {
  font-family: 'DM Mono', monospace;
  font-size: .85rem;
  color: var(--accent2);
  margin-bottom: .6rem;
  font-weight: 500;
}
.fn-def {
  font-size: .9rem;
  line-height: 2.4;
  margin-bottom: .5rem;
  color: var(--text);
}
.fn-recip {
  font-family: 'DM Mono', monospace;
  font-size: .68rem;
  color: var(--muted);
  letter-spacing: .04em;
  margin-top: .3rem;
  border-top: 1px solid var(--border);
  padding-top: .4rem;
}

/* .six — 3-column grid used in trig six-functions card */
.six {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: .7rem;
  margin-top: .6rem;
}
@media (max-width: 760px) { .six { grid-template-columns: 1fr 1fr; } }
@media (max-width: 480px) { .six { grid-template-columns: 1fr; } }

/* transformation pill (trig graph explorer) */
.t-pill {
  display: flex;
  gap: .7rem;
  align-items: flex-start;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: .8rem;
}
.t-key {
  font-family: 'DM Mono', monospace;
  font-size: 1rem;
  color: var(--accent);
  font-weight: 600;
  flex-shrink: 0;
  min-width: 18px;
}
.t-desc { font-size: .82rem; color: var(--muted); line-height: 1.6; }

/* id-card (identity display in trig) */
.id-card {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2rem;
  text-align: center;
}
.id-formula { font-size: 1.05rem; line-height: 3; margin-bottom: .4rem; }
.id-desc { font-size: .82rem; color: var(--muted); line-height: 1.6; }

/* CAST diagram wrapper */
.cast-wrap { display: flex; justify-content: center; }


/* ─── Canvas ─── */
canvas { display: block; width: 100%; border-radius: 6px; }

/* ─── Graph wrapper ─── */
.graph-wrap {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: .8rem;
}
.graph-lbl {
  font-family: 'DM Mono', monospace;
  font-size: .7rem;
  letter-spacing: .06em;
  margin-bottom: .4rem;
}

/* ─── Divider ─── */
.divider { height: 1px; background: var(--border); margin: 1.5rem 0; }

/* ─── Tables ─── */
.exact-table {
  width: 100%;
  border-collapse: separate;
  border-spacing: 0;
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid var(--border);
}
.exact-table th {
  background: hsla(36, 33%, 90%, 0.5);
  padding: 1rem;
  font-size: .76rem;
  color: var(--muted);
  border-bottom: 1px solid var(--border);
}
.exact-table td {
  padding: 1rem;
  text-align: center;
  border-bottom: 1px solid var(--border);
  background: #fff;
}

/* Tags */
.tag { display:inline-block; font-family:'DM Mono',monospace; font-size:.65rem; letter-spacing:.07em; padding:2px 8px; border-radius:3px; text-transform:uppercase; margin-right:.3rem; }
.tag-key{background:#ede9fe;color:#5b21b6;} .tag-exam{background:#fce7f3;color:#9d174d;} .tag-method{background:#e0f2fe;color:#075985;}

/* ════════════════════════════════════════════
   PRACTICE QUESTIONS
   ════════════════════════════════════════════ */
.q-block { margin-bottom: 1.4rem; }
.q-diff {
  display: inline-block;
  font-family: 'DM Mono', monospace;
  font-size: .68rem;
  letter-spacing: .08em;
  padding: 2px 8px;
  border-radius: 3px;
  margin-bottom: .5rem;
}
.q-diff.easy { background: var(--easy); color: var(--easy-text); }
.q-diff.med  { background: var(--med);  color: var(--med-text);  }
.q-diff.hard { background: var(--hard); color: var(--hard-text); }

.q-text {
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1.1rem 1.3rem;
  font-size: .95rem;
  line-height: 2.1;
  border-left: 3px solid var(--border);
}
.q-text.easy { border-left-color: var(--easy-text); }
.q-text.med  { border-left-color: var(--med-text);  }
.q-text.hard { border-left-color: var(--hard-text); }
.q-marks { font-family: 'DM Mono', monospace; font-size: .8rem; color: var(--muted); float: right; }

.ans-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--muted);
  font-size: .8rem;
  padding: 5px 14px;
  cursor: pointer;
  margin-top: .6rem;
  font-family: 'DM Sans', sans-serif;
  transition: all .15s;
}
.ans-btn:hover { border-color: var(--accent); color: var(--accent); }

.ans-box {
  display: none;
  background: #f5f0e8;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: .9rem 1.1rem;
  margin-top: .6rem;
  font-size: .9rem;
  line-height: 2.1;
}

/* Structured answer box (ch10 style) */
.ans-box.structured { background: none; padding: 0; }
.ans-header { background: var(--surface2); padding: .6rem 1rem; font-family: 'DM Mono', monospace; font-size: .68rem; letter-spacing: .1em; color: var(--muted); text-transform: uppercase; border-bottom: 1px solid var(--border); border: 1px solid var(--border); border-radius: 8px 8px 0 0; }
.ans-body { padding: 1rem 1.1rem; border: 1px solid var(--border); border-top: none; border-radius: 0 0 8px 8px; background: #fff; }
.ans-step-row { display: grid; grid-template-columns: 90px 1fr; gap: .7rem; padding: .45rem 0; border-bottom: 1px solid var(--border); align-items: baseline; font-size: .88rem; line-height: 1.9; }
.ans-step-row:last-child { border-bottom: none; }
.ans-step-label { font-family: 'DM Mono', monospace; font-size: .7rem; color: var(--muted); }
.ans-step-content { color: var(--text); }
.ans-conclusion { margin-top: .8rem; background: var(--surface2); border-left: 3px solid var(--accent3); border-radius: 0 6px 6px 0; padding: .7rem 1rem; font-size: .9rem; line-height: 2; }

/* Resource link */
.res-link {
  display: flex;
  align-items: flex-start;
  gap: .9rem;
  text-decoration: none;
  color: var(--text);
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1rem 1.2rem;
  margin-bottom: .7rem;
  transition: all .2s;
}
.res-link:hover { border-color: var(--accent); transform: translateY(-1px); box-shadow: 0 4px 16px rgba(0,0,0,.06); }
.res-name { font-weight: 600; font-size: .9rem; margin-bottom: .2rem; }
.res-desc { font-size: .8rem; color: var(--muted); line-height: 1.5; }

/* ════════════════════════════════════════════
   QOL TOOLBAR PANELS
   ════════════════════════════════════════════ */
/* Timer display (in topbar) */
.timer-display {
  font-family: 'DM Mono', monospace;
  font-size: .9rem;
  color: var(--brand-black);
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 3px 10px;
  min-width: 58px;
  text-align: center;
  cursor: pointer;
  transition: all .15s;
}
.timer-display.running { border-color: var(--accent3); color: var(--accent3); }
.timer-display.warning { border-color: var(--accent2); color: var(--accent2); animation: pe-pulse .8s infinite; }
@keyframes pe-pulse { 0%,100%{opacity:1;} 50%{opacity:.5;} }

/* Timer panel (fixed floating) */
.timer-panel {
  display: none;
  position: fixed;
  top: 76px;
  right: 1.5rem;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.2rem;
  z-index: 200;
  min-width: 200px;
  box-shadow: 0 8px 32px rgba(0,0,0,.12);
}
.timer-panel.open { display: block; }

.timer-preset { display: grid; grid-template-columns: 1fr 1fr; gap: .4rem; margin-bottom: .7rem; }
.t-preset {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 5px;
  color: var(--muted);
  font-family: 'DM Mono', monospace;
  font-size: .72rem;
  padding: 5px 8px;
  cursor: pointer;
  text-align: center;
  transition: all .15s;
}
.t-preset:hover { border-color: var(--accent); color: var(--text); }

/* Checklist panel (fixed floating) */
.checklist-panel {
  display: none;
  position: fixed;
  top: 76px;
  right: 1.5rem;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1rem 1.2rem;
  z-index: 200;
  min-width: 240px;
  box-shadow: 0 8px 32px rgba(0,0,0,.12);
}
.checklist-panel.open { display: block; }

.check-item {
  display: flex;
  align-items: center;
  gap: .6rem;
  padding: .5rem 0;
  border-bottom: 1px solid var(--border);
  cursor: pointer;
  font-size: .88rem;
  color: var(--muted);
  transition: color .15s;
}
.check-item:last-child { border-bottom: none; }
.check-item.done { color: var(--accent3); }
.check-box {
  width: 16px; height: 16px;
  border: 1px solid var(--border);
  border-radius: 3px;
  flex-shrink: 0;
  display: flex; align-items: center; justify-content: center;
  font-size: .7rem;
}
.check-item.done .check-box { background: var(--accent3); border-color: var(--accent3); color: #fff; }

/* ════════════════════════════════════════════
   FULLSCREEN & HINTS
   ════════════════════════════════════════════ */
body.fullscreen .topbar { display: none; }
body.fullscreen .main { max-width: 100%; padding: 1.5rem 2rem; }
body.fullscreen .fs-hint { display: flex; }

.fs-hint {
  display: none;
  position: fixed;
  bottom: 1rem; right: 1rem;
  z-index: 300;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: .4rem .8rem;
  font-family: 'DM Mono', monospace;
  font-size: .7rem;
  color: var(--muted);
}
.kb-hint {
  position: fixed;
  bottom: 1rem; left: 1rem;
  z-index: 200;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: .5rem .9rem;
  font-family: 'DM Mono', monospace;
  font-size: .7rem;
  color: var(--muted);
  display: none;
}
.kb-hint.visible { display: block; }

/* ════════════════════════════════════════════
   ACCESS CONTROL — "Coming Soon" blur layer
   ════════════════════════════════════════════ */
.content-locked {
  filter: blur(5px);
  pointer-events: none;
  user-select: none;
  position: relative;
}

.premium-cta-box {
  position: relative;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 2rem;
  text-align: center;
  margin: 2rem 0;
  box-shadow: 0 4px 24px rgba(0,0,0,.08);
  z-index: 10;
}
.premium-cta-box .cta-icon { font-size: 2rem; margin-bottom: .8rem; }
.premium-cta-box .cta-title {
  font-family: 'Cormorant Garamond', serif;
  font-size: 1.5rem;
  font-weight: 500;
  margin-bottom: .4rem;
  color: var(--brand-black);
}
.premium-cta-box .cta-sub { color: var(--muted); font-size: .88rem; line-height: 1.7; margin-bottom: 1.2rem; }
.premium-cta-box .cta-btn {
  display: inline-block;
  background: var(--brand-black);
  color: #fff;
  padding: .7rem 2rem;
  border-radius: 50px;
  font-size: .9rem;
  font-weight: 600;
  text-decoration: none;
  font-family: 'DM Sans', sans-serif;
  transition: all .2s;
}
.premium-cta-box .cta-btn:hover { background: #333; transform: translateY(-1px); }

/* ════════════════════════════════════════════
   SUBJECT HUB PAGE  (subjects hub pages)
   ════════════════════════════════════════════ */
.hub-hero {
  padding: 3rem 2rem 2rem;
  max-width: 900px;
  margin: 0 auto;
}
.hub-eyebrow {
  font-family: 'DM Mono', monospace;
  font-size: .68rem;
  letter-spacing: .14em;
  color: var(--accent);
  text-transform: uppercase;
  margin-bottom: 1rem;
}
.hub-title {
  font-family: 'Cormorant Garamond', serif;
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 500;
  margin-bottom: .4rem;
  line-height: 1.15;
  letter-spacing: -.02em;
}
.hub-sub { color: var(--muted); font-size: .95rem; line-height: 1.7; max-width: 500px; }

.chapters-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 1rem;
  max-width: 900px;
  margin: 2rem auto;
  padding: 0 2rem 3rem;
}
.chapter-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.4rem;
  text-decoration: none;
  color: var(--text);
  transition: all .2s;
  display: block;
  position: relative;
}
.chapter-card:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: 0 8px 24px rgba(0,0,0,.07); }
.chapter-card.locked { opacity: .55; cursor: default; }
.chapter-card.locked:hover { transform: none; box-shadow: none; border-color: var(--border); }
.ch-num {
  font-family: 'DM Mono', monospace;
  font-size: .62rem;
  letter-spacing: .1em;
  color: var(--muted);
  margin-bottom: .5rem;
  text-transform: uppercase;
}
.ch-title { font-size: .95rem; font-weight: 600; margin-bottom: .4rem; }
.ch-desc { font-size: .78rem; color: var(--muted); line-height: 1.5; }
.ch-badge {
  font-family: 'DM Mono', monospace;
  font-size: .58rem;
  letter-spacing: .1em;
  padding: 2px 7px;
  border-radius: 3px;
  margin-top: .7rem;
  display: inline-block;
}
.ch-badge.avail { background: #dcfce7; color: var(--easy-text); }
.ch-badge.soon  { background: var(--surface2); color: var(--muted2); border: 1px solid var(--border); }
.lock-badge { position: absolute; top: .9rem; right: .9rem; font-size: .9rem; opacity: .35; }

/* Slider row (shared) */
.slider-row { display: flex; align-items: center; gap: .8rem; margin-bottom: .6rem; }
.slider-row label { font-family: 'DM Mono', monospace; font-size: .78rem; color: var(--muted); min-width: 36px; }
.slider-row input[type=range] { flex: 1; accent-color: var(--accent); }
.slider-row .val { font-family: 'DM Mono', monospace; font-size: .82rem; color: var(--accent); min-width: 44px; text-align: right; }

/* ════════════════════════════════════════════
   RESPONSIVE
   ════════════════════════════════════════════ */
@media (max-width: 760px) {
  .c2, .c3 { grid-template-columns: 1fr; }
  .nav-btn { padding: 0 .5rem; font-size: .72rem; }
  .main { padding: 1.5rem 1rem; }
  .subject-switcher { display: none; }
  .ans-step-row { grid-template-columns: 65px 1fr; }
  .chapters-grid { grid-template-columns: 1fr; }
}
@media (max-width: 500px) {
  .logo { font-size: 1.1rem; }
  .logo-badge { display: none; }
}