@font-face {
  font-family: 'Thmanyah';
  src: url('fonts/thmanyah-sans-Regular.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: 'Thmanyah';
  src: url('fonts/thmanyah-sans-Bold.woff2') format('woff2');
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

:root {
  --navy: #1F4E79;
  --navy-dark: #16324F;
  --orange: #E8722A;
  --blue: #2E6FB7;
  --green: #2E7D4F;
  --paper: #F6F3EB;
  --paper-2: #EFEAD9;
  --ink: #22303C;
  --muted: #6E7972;
  --desk-1: #2B2118;
  --desk-2: #1C150F;
  --gold: #C49A4B;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: 'Thmanyah', 'IBM Plex Sans Arabic', system-ui, sans-serif;
  background: radial-gradient(1200px 700px at 50% 18%, var(--desk-1), var(--desk-2));
  color: var(--ink);
  min-height: 100vh;
}

#desk {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 18px;
}

#book { width: 100%; max-width: 1240px; }
.hidden { display: none !important; }

/* ---------- الغلاف ---------- */
#cover {
  background: linear-gradient(160deg, #22486B 0%, var(--navy) 55%, var(--navy-dark) 100%);
  border-radius: 14px;
  box-shadow: 0 30px 60px rgba(0,0,0,.55), inset 0 0 0 1px rgba(255,255,255,.08);
  color: #F6F3EB;
  text-align: center;
  padding: 64px 28px 52px;
  position: relative;
  overflow: hidden;
}
#cover::before {
  content: "";
  position: absolute; inset: 0;
  background: radial-gradient(600px 300px at 80% -10%, rgba(232,114,42,.28), transparent 60%),
              radial-gradient(500px 260px at 10% 110%, rgba(46,111,183,.35), transparent 60%);
  pointer-events: none;
}
.cover-inner { position: relative; z-index: 1; }
.cover-kicker { font-size: 17px; color: var(--gold); letter-spacing: .5px; margin-bottom: 10px; }
.cover-chapter { font-size: 30px; margin: 0 0 6px; font-weight: 700; }
.cover-title { font-size: 64px; line-height: 1.15; margin: 0 0 18px; font-weight: 700; }
.cover-wave { margin: 6px auto 20px; opacity: .95; }
.cover-teacher { font-size: 22px; margin-bottom: 26px; }
.cover-physics {
  font-size: 15px; letter-spacing: 10px; color: #D9C9A3;
  border: 1px solid rgba(217,201,163,.55); border-radius: 999px;
  display: inline-block; padding: 8px 22px 8px 14px; margin-bottom: 34px;
}
.btn {
  font-family: inherit; cursor: pointer; border: none; border-radius: 999px;
  background: var(--orange); color: #fff; font-weight: 700;
  padding: 12px 22px; font-size: 17px;
  box-shadow: 0 6px 18px rgba(232,114,42,.4);
  transition: transform .12s ease, box-shadow .12s ease, background .12s ease;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 10px 22px rgba(232,114,42,.5); }
.btn:active { transform: translateY(0); }
.btn-big { font-size: 21px; padding: 15px 44px; }
.btn-ghost {
  background: #fff; color: var(--navy); border: 2px solid var(--navy);
  box-shadow: none; padding: 9px 18px; font-size: 15px;
}
.btn-ghost.active { background: var(--navy); color: #fff; }
.cover-hint { margin-top: 22px; font-size: 14px; color: rgba(246,243,235,.75); }

/* ---------- الكتاب المفتوح ---------- */
.spread {
  display: flex;
  border-radius: 14px;
  overflow: hidden;
  box-shadow: 0 30px 60px rgba(0,0,0,.55);
  background: var(--paper);
  min-height: 640px;
}
.page { background: var(--paper); }
.text-page {
  flex: 1 1 46%;
  padding: 26px 30px 22px;
  overflow-y: auto;
  max-height: 640px;
  border-left: 1px solid rgba(31,78,121,.18);
  box-shadow: inset -18px 0 26px -18px rgba(0,0,0,.35);
  position: relative;
}
.scene-page {
  flex: 1 1 54%;
  display: flex; flex-direction: column;
  background: linear-gradient(180deg, #F8F5EC, var(--paper));
  box-shadow: inset 18px 0 26px -18px rgba(0,0,0,.35);
  min-width: 0;
}
#scene-container { flex: 1 1 auto; min-height: 420px; position: relative; touch-action: none; }
#scene-container canvas { display: block; width: 100% !important; height: 100% !important; }
.scene-caption {
  text-align: center; font-size: 14px; color: var(--muted);
  padding: 2px 14px 6px; min-height: 22px;
}
.scene-controls {
  display: flex; flex-wrap: wrap; gap: 8px; align-items: center; justify-content: center;
  padding: 10px 14px 16px;
  border-top: 1px solid rgba(31,78,121,.14);
  background: rgba(255,255,255,.45);
}
.scene-controls .ctl-label { font-size: 14px; color: var(--navy); font-weight: 700; }
.scene-controls input[type="range"] {
  accent-color: var(--orange);
  width: 170px; height: 26px; cursor: pointer;
}
.scene-controls .readout {
  font-size: 15px; font-weight: 700; color: var(--navy);
  background: #fff; border: 1px solid rgba(31,78,121,.25); border-radius: 10px;
  padding: 6px 12px;
}
.scene-controls .readout b { color: var(--orange); }
.mini-btn {
  font-family: inherit; cursor: pointer; border-radius: 999px;
  border: 2px solid var(--navy); background: #fff; color: var(--navy);
  font-weight: 700; font-size: 15px; padding: 8px 16px; min-height: 40px;
}
.mini-btn:hover { background: #EAF1F8; }
.mini-btn.active { background: var(--navy); color: #fff; }
.mini-btn.orange { border-color: var(--orange); color: var(--orange); }
.mini-btn.orange.active { background: var(--orange); color: #fff; }
.mini-btn.blue { border-color: var(--blue); color: var(--blue); }
.mini-btn.blue.active { background: var(--blue); color: #fff; }

/* ---------- صفحة النص ---------- */
.text-page h2 {
  color: var(--navy); font-size: 25px; line-height: 1.35; margin: 2px 0 4px;
}
.text-page .src-pages { font-size: 13px; color: var(--muted); margin-bottom: 12px; }
.text-page .summary { font-size: 16.5px; line-height: 1.9; margin: 0 0 14px; }
.eq-box {
  background: #fff; border: 2px solid var(--orange); border-radius: 12px;
  padding: 12px 16px; margin: 0 0 14px; text-align: center;
}
.eq-box .eq-label { font-size: 14px; color: var(--muted); margin-bottom: 4px; }
.eq-box .eq-formula { font-size: 24px; font-weight: 700; color: var(--navy); }
.eq-box .eq-formula .frac { display: inline-block; vertical-align: middle; text-align: center; font-size: 20px; }
.eq-box .eq-formula .frac .num { display: block; border-bottom: 2px solid var(--navy); padding: 0 8px; }
.eq-box .eq-formula .frac .den { display: block; padding: 0 8px; }
.formula-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin: 0 0 14px; }
.formula-grid .eq-box { margin: 0; padding: 9px 10px; }
.formula-grid .eq-box .eq-formula { font-size: 19px; }
.formula-grid .eq-box .eq-label { font-size: 12.5px; }
.worked-box {
  background: #FFF7EC; border: 1px dashed var(--orange); border-radius: 12px;
  padding: 12px 16px; margin: 0 0 14px; font-size: 15.5px; line-height: 1.9;
}
.worked-box .wb-label { font-weight: 700; color: var(--orange); margin-bottom: 4px; }
.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 0 0 14px; }
.compare .cmp {
  background: #fff; border-radius: 12px; padding: 12px 14px;
  border-top: 4px solid var(--orange); font-size: 14.5px; line-height: 1.8;
}
.compare .cmp.q { border-top-color: var(--blue); }
.compare .cmp h4 { margin: 0 0 6px; color: var(--navy); font-size: 15.5px; }
.compare .cmp ul { margin: 0; padding-right: 18px; }
.terms { margin: 0 0 14px; }
.terms h3, .sec-title {
  color: var(--navy); font-size: 17px; margin: 0 0 8px;
  border-bottom: 2px solid rgba(31,78,121,.2); padding-bottom: 4px;
}
.terms dl { margin: 0; }
.terms dt { font-weight: 700; color: var(--orange); font-size: 15.5px; }
.terms dd { margin: 0 0 8px; font-size: 15px; line-height: 1.8; }
.predict-box {
  background: #EAF1F8; border-radius: 12px; padding: 13px 16px; margin: 0 0 14px;
}
.predict-box .pb-tag { font-size: 13px; font-weight: 700; color: var(--blue); margin-bottom: 4px; }
.predict-box .pb-q { font-size: 16px; font-weight: 700; line-height: 1.8; margin-bottom: 10px; }
.predict-box .pb-a {
  display: none; background: #fff; border-radius: 8px; padding: 10px 12px;
  font-size: 15.5px; line-height: 1.9; margin-top: 10px; border-right: 4px solid var(--blue);
}
.predict-box.revealed .pb-a { display: block; }
.quote-box {
  font-family: 'Amiri', serif; font-size: 19px; line-height: 2;
  color: #4A4438; background: var(--paper-2); border-radius: 12px;
  padding: 14px 18px; margin: 0 0 14px;
}
.quote-box .q-by { font-family: 'Thmanyah', 'IBM Plex Sans Arabic', sans-serif; font-size: 15px; font-weight: 700; color: var(--navy); margin-top: 8px; }
.extra-note { font-size: 15px; line-height: 1.9; background: #fff; border-radius: 12px; padding: 12px 16px; margin: 0 0 14px; }
.stage-line {
  background: #FFF7EC; border-right: 4px solid var(--orange); border-radius: 8px;
  padding: 10px 14px; font-size: 15px; line-height: 1.9; margin: 0 0 14px;
}
.stage-line b { color: var(--navy); }
.stamp {
  display: none; position: absolute; top: 16px; left: 16px;
  border: 3px solid var(--green); color: var(--green); border-radius: 10px;
  font-weight: 700; font-size: 15px; padding: 4px 12px; transform: rotate(-6deg);
  background: rgba(255,255,255,.75);
}
.stamp.show { display: block; }

/* ---------- شريط التنقل ---------- */
.hud {
  display: flex; align-items: center; justify-content: space-between; gap: 10px;
  margin-top: 14px; background: rgba(246,243,235,.92); border-radius: 999px;
  padding: 8px 12px; box-shadow: 0 10px 24px rgba(0,0,0,.35);
}
.hud-btn { padding: 9px 20px; font-size: 15px; }
.hud-btn:disabled { opacity: .45; box-shadow: none; cursor: default; transform: none; }
.dots { display: flex; gap: 8px; }
.dots .dot {
  width: 12px; height: 12px; border-radius: 50%; border: 2px solid var(--navy);
  background: transparent; cursor: pointer; padding: 0;
}
.dots .dot.active { background: var(--orange); border-color: var(--orange); }
.page-counter { font-size: 14px; color: var(--navy); font-weight: 700; white-space: nowrap; }

.ltr { direction: ltr; unicode-bidi: isolate; }

/* ---------- متجاوب ---------- */
@media (max-width: 900px) {
  #desk { padding: 10px; align-items: flex-start; }
  .spread { flex-direction: column; min-height: 0; }
  .text-page { max-height: none; border-left: none; border-bottom: 1px solid rgba(31,78,121,.18); box-shadow: none; order: 1; }
  .scene-page { order: 2; }
  #scene-container { min-height: 340px; }
  .cover-title { font-size: 44px; }
  .hud { border-radius: 16px; flex-wrap: wrap; justify-content: center; }
}