/* ============================================================
   每一焦耳 · 3D 能量课本 —— 纸书风，暖米纸 + 墨线
   ============================================================ */
:root{
  --paper:#f7f2e7;        /* 桌面暖米 */
  --page:#fffdf7;         /* 书页 */
  --ink:#2b2620;          /* 墨线 */
  --ink-soft:#6b6154;
  --accent:#c4562a;       /* 铁锈橙 */
  --accent-soft:#e8d5c4;
  --hair:#e3d9c6;
  --ok:#2c7a4b;
  /* 八色储能 */
  --s-kinetic:#2f7bff;
  --s-grav:#8a4dff;
  --s-elastic:#ff3fb4;
  --s-thermal:#ff7a1c;
  --s-chem:#e8233a;
  --s-mag:#26c75a;
  --s-elect:#18c4dc;
  --s-nuclear:#ffcf1a;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:"PingFang SC","Hiragino Sans GB","Noto Sans SC","Microsoft YaHei",sans-serif;
  line-height:1.75;
  -webkit-font-smoothing:antialiased;
}

/* ---------- 加载 ---------- */
#loading{
  position:fixed;inset:0;z-index:1000;
  background:var(--paper);
  display:flex;flex-direction:column;align-items:center;justify-content:center;gap:22px;
  transition:opacity .5s ease;
}
#loading.done{opacity:0;pointer-events:none}
.load-dot{
  width:14px;height:14px;border-radius:50%;
  animation:stores 2.4s linear infinite, bob 1.2s ease-in-out infinite;
  box-shadow:0 0 18px 4px currentColor;
}
@keyframes stores{
  0%{color:#2f7bff;background:#2f7bff}
  12.5%{color:#8a4dff;background:#8a4dff}
  25%{color:#ff3fb4;background:#ff3fb4}
  37.5%{color:#ff7a1c;background:#ff7a1c}
  50%{color:#e8233a;background:#e8233a}
  62.5%{color:#26c75a;background:#26c75a}
  75%{color:#18c4dc;background:#18c4dc}
  87.5%{color:#ffcf1a;background:#ffcf1a}
  100%{color:#2f7bff;background:#2f7bff}
}
@keyframes bob{0%,100%{transform:translateY(0)}50%{transform:translateY(-8px)}}
.load-text{font-size:13px;letter-spacing:.35em;color:var(--ink-soft)}

/* ---------- 返回导航（独立页必带，置于可复制区之外） ---------- */
.backnav{
  max-width:1180px;margin:0 auto;padding:14px 24px 0;
  display:flex;gap:22px;font-size:13px;
}
.backnav a{color:var(--ink-soft);text-decoration:none;border-bottom:1px solid transparent;transition:.2s}
.backnav a:hover{color:var(--accent);border-bottom-color:var(--accent)}

/* ---------- 头部 ---------- */
.site-head{
  max-width:1180px;margin:0 auto;padding:10px 24px 18px;
  display:flex;align-items:flex-end;justify-content:space-between;gap:16px;
  border-bottom:2px solid var(--ink);
}
.brand-main{
  font-family:"Songti SC","STSong","Noto Serif SC",serif;
  font-size:clamp(28px,4vw,42px);font-weight:900;letter-spacing:.06em;display:block;
}
.brand-sub{font-size:11px;letter-spacing:.28em;color:var(--ink-soft);text-transform:uppercase}
.stamps{display:flex;gap:8px}
.seal{
  width:40px;height:40px;border-radius:50%;
  border:2px solid var(--hair);color:var(--hair);
  display:flex;align-items:center;justify-content:center;
  font-family:"Songti SC",serif;font-size:15px;font-weight:700;
  transition:.35s;
}
.seal.on{border-color:var(--accent);color:#fff;background:var(--accent);box-shadow:0 3px 12px rgba(196,86,42,.35)}

/* ---------- 目录 tab ---------- */
.tabs{
  max-width:1180px;margin:0 auto;padding:16px 24px 0;
  display:flex;flex-wrap:wrap;gap:10px;
}
.tab{
  padding:9px 20px;border-radius:999px;cursor:pointer;
  border:1.5px solid var(--ink);background:transparent;color:var(--ink);
  font-size:14px;font-weight:600;letter-spacing:.04em;transition:.2s;
}
.tab:hover{background:var(--accent-soft)}
.tab.active{background:var(--ink);color:var(--page)}

/* ---------- 书页布局 ---------- */
#book{max-width:1180px;margin:0 auto;padding:22px 24px 40px}
.spread{animation:fadein .45s ease}
@keyframes fadein{from{opacity:0;transform:translateY(14px)}to{opacity:1;transform:none}}

.cover{
  background:var(--page);
  border:2px solid var(--ink);border-radius:6px;
  box-shadow:6px 6px 0 var(--accent-soft);
  padding:clamp(28px,5vw,70px);
}
.cover-frame{max-width:760px;margin:0 auto;text-align:center}
.cover-kicker{font-size:11px;letter-spacing:.5em;color:var(--accent);margin-bottom:18px}
.cover-title{
  font-family:"Songti SC","STSong","Noto Serif SC",serif;
  font-size:clamp(52px,9vw,110px);font-weight:900;letter-spacing:.12em;line-height:1.1;
}
.cover-line{font-size:clamp(16px,2.2vw,22px);color:var(--ink-soft);margin:26px 0 34px;line-height:2}
.cover-stores{display:flex;flex-wrap:wrap;justify-content:center;gap:10px;margin-bottom:38px}
.cs-chip{
  display:flex;align-items:center;gap:7px;
  padding:7px 14px;border-radius:999px;border:1.5px solid var(--hair);
  font-size:12.5px;font-weight:600;background:#fff;
}
.cs-dot{width:10px;height:10px;border-radius:50%}
.btn-open{
  padding:15px 46px;border-radius:999px;cursor:pointer;
  border:2px solid var(--ink);background:var(--ink);color:var(--page);
  font-size:17px;font-weight:700;letter-spacing:.12em;transition:.25s;
}
.btn-open:hover{background:var(--accent);border-color:var(--accent);transform:translateY(-2px)}
.cover-note{margin-top:30px;font-size:12px;color:var(--ink-soft);line-height:2}

/* 课程跨页：左文右实验 */
.spread[hidden]{display:none !important}
#spread-l1,#spread-l2,#spread-l3{
  display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.15fr);gap:22px;align-items:start;
}
.page-left,.page-right{
  background:var(--page);
  border:2px solid var(--ink);border-radius:6px;
  padding:clamp(18px,2.6vw,32px);
}
.page-left{box-shadow:6px 6px 0 var(--accent-soft)}
.page-right{box-shadow:6px 6px 0 var(--hair)}

.lesson-no{font-size:10.5px;letter-spacing:.42em;color:var(--accent);font-weight:700}
.lesson-title{
  font-family:"Songti SC","STSong","Noto Serif SC",serif;
  font-size:clamp(28px,3.6vw,42px);font-weight:900;letter-spacing:.06em;margin:6px 0 12px;
}
.lesson-lead{font-size:15px;color:var(--ink);margin-bottom:18px}
.lesson-lead strong{color:var(--accent)}

.formula-card{
  border:1.5px solid var(--ink);border-radius:8px;
  padding:14px 18px;margin-bottom:16px;background:#fff;
}
.formula-card .f{font-family:"Times New Roman",serif;font-size:clamp(19px,2.4vw,25px);font-style:italic;font-weight:700;letter-spacing:.03em}
.formula-card .f-note{font-size:11.5px;color:var(--ink-soft);margin-top:5px;letter-spacing:.05em}

.keywords{list-style:none;margin-bottom:20px}
.keywords li{
  position:relative;padding:6px 0 6px 20px;font-size:13.5px;color:var(--ink-soft);
  border-bottom:1px dashed var(--hair);
}
.keywords li::before{content:"◆";position:absolute;left:2px;top:6px;font-size:9px;color:var(--accent)}
.keywords b{color:var(--ink)}

/* 预测区 */
.predict{border:2px solid var(--ink);border-radius:8px;padding:16px 18px;background:#fffdf3}
.predict-title{font-size:11px;letter-spacing:.32em;color:var(--accent);font-weight:700;margin-bottom:8px}
.predict-q{font-size:15px;font-weight:700;margin-bottom:12px}
.options{display:flex;flex-direction:column;gap:8px}
.opt{
  text-align:left;padding:10px 14px;border-radius:8px;cursor:pointer;
  border:1.5px solid var(--hair);background:#fff;font-size:13.5px;color:var(--ink);
  transition:.18s;font-family:inherit;line-height:1.55;
}
.opt:hover{border-color:var(--ink)}
.opt.picked{border-color:var(--accent);background:#fdf1e9;font-weight:700}
.opt.right{border-color:var(--ok);background:#eaf6ee;color:var(--ok);font-weight:700}
.opt.wrong{opacity:.55;text-decoration:line-through}

/* 掀盖 flap */
.flap-wrap{margin-top:14px}
.flap-btn{
  padding:9px 22px;border-radius:999px;cursor:pointer;
  border:1.5px solid var(--accent);background:var(--accent);color:#fff;
  font-size:13px;font-weight:700;letter-spacing:.06em;font-family:inherit;transition:.2s;
}
.flap-btn:disabled{opacity:.35;cursor:not-allowed}
.flap-btn:not(:disabled):hover{transform:translateY(-1px);box-shadow:0 4px 12px rgba(196,86,42,.3)}
.flap{margin-top:12px;position:relative}
.flap-cover{
  padding:12px 16px;border-radius:8px 8px 0 0;cursor:pointer;
  background:repeating-linear-gradient(45deg,#f3e9d6,#f3e9d6 8px,#efe3cc 8px,#efe3cc 16px);
  border:1.5px solid var(--ink);border-bottom:none;
  font-size:12px;letter-spacing:.18em;color:var(--ink-soft);text-align:center;font-weight:700;
}
.flap-body{
  display:none;padding:15px 17px;border-radius:0 0 8px 8px;
  border:1.5px solid var(--ink);background:#fff;font-size:13.5px;line-height:1.9;
}
.flap.open .flap-body{display:block;animation:fadein .35s ease}
.flap.open .flap-cover{opacity:.55}
.flap-body b{color:var(--accent)}
.flap-body strong{color:var(--ink)}

/* 挑战 */
.challenge{
  display:flex;align-items:center;gap:12px;flex-wrap:wrap;
  margin:18px 0 12px;padding:12px 16px;border-radius:8px;
  background:var(--ink);color:var(--page);
}
.ch-tag{font-size:10px;letter-spacing:.3em;padding:3px 10px;border:1px solid var(--page);border-radius:999px;flex-shrink:0}
.ch-text{font-size:13px;font-weight:600}

.lesson-nav{display:flex;justify-content:space-between;gap:10px;margin-top:16px}
.btn-next{
  padding:8px 16px;border-radius:999px;cursor:pointer;
  border:1.5px solid var(--ink);background:transparent;color:var(--ink);
  font-size:12.5px;font-weight:600;font-family:inherit;transition:.2s;
}
.btn-next:hover{background:var(--ink);color:var(--page)}

/* 右页实验台 */
.stage-wrap{
  position:relative;border-radius:8px;overflow:hidden;
  border:1.5px solid var(--ink);background:#fff;
  aspect-ratio:4/3;min-height:320px;
}
.stage-wrap canvas{width:100%;height:100%;display:block;cursor:grab;touch-action:none}
.stage-wrap canvas:active{cursor:grabbing}
.stage-hint{
  position:absolute;left:50%;bottom:12px;transform:translateX(-50%);
  padding:7px 18px;border-radius:999px;pointer-events:none;
  background:rgba(43,38,32,.82);color:#fff;font-size:12px;letter-spacing:.06em;
  transition:opacity .4s;white-space:nowrap;
}
.stage-hint.hide{opacity:0}

.controls{display:flex;align-items:center;gap:12px;flex-wrap:wrap;margin:12px 0}
.seg{display:flex;border:1.5px solid var(--ink);border-radius:999px;overflow:hidden}
.seg-btn{
  padding:7px 18px;border:none;cursor:pointer;background:transparent;
  font-size:12.5px;font-weight:700;font-family:inherit;color:var(--ink);transition:.18s;
}
.seg-btn.active{background:var(--ink);color:var(--page)}
.btn-mini{
  padding:7px 16px;border-radius:999px;cursor:pointer;
  border:1.5px solid var(--ink);background:#fff;color:var(--ink);
  font-size:12.5px;font-weight:600;font-family:inherit;transition:.18s;
}
.btn-mini:hover{background:var(--ink);color:var(--page)}
.readout{
  margin-left:auto;font-size:12px;letter-spacing:.06em;color:var(--ink-soft);
  font-variant-numeric:tabular-nums;background:#fff;
  padding:6px 14px;border-radius:999px;border:1px solid var(--hair);
}

/* 能量罐 */
.jarbar{
  display:flex;gap:8px;justify-content:space-between;flex-wrap:wrap;
  margin-top:12px;
}
.jarbar.grid8{
  display:grid;grid-template-columns:repeat(4,1fr);gap:10px 8px;
}
.jarbar.grid8 .jar{max-width:none}
.jar{
  flex:1 1 0;min-width:62px;max-width:120px;
  display:flex;flex-direction:column;align-items:center;gap:6px;
}
.jar-name{font-size:10.5px;color:var(--ink-soft);letter-spacing:.04em;text-align:center;font-weight:600;min-height:28px;display:flex;align-items:flex-end;justify-content:center}
.jar-glass{
  width:34px;height:96px;border-radius:7px 7px 12px 12px;position:relative;overflow:hidden;
  border:2px solid var(--ink);background:#fff;
}
.jar-glass::before{
  content:"";position:absolute;top:0;left:0;right:0;height:8px;
  background:repeating-linear-gradient(90deg,transparent,transparent 3px,rgba(43,38,32,.18) 3px,rgba(43,38,32,.18) 5px);
}
.jar-fill{
  position:absolute;left:0;right:0;bottom:0;height:0%;
  transition:height .18s ease;
  border-radius:0 0 9px 9px;
}
.jar-val{font-size:11px;font-variant-numeric:tabular-nums;font-weight:700;letter-spacing:.02em}
.jar.total .jar-glass{border-style:dashed}

/* 页脚 */
.site-foot{
  max-width:1180px;margin:0 auto;padding:26px 24px 60px;
  border-top:2px solid var(--ink);
  font-size:12px;color:var(--ink-soft);line-height:2.1;
}
.site-foot p{margin-bottom:8px}
.site-foot b{color:var(--ink)}

/* ---------- 响应式 ---------- */
@media (max-width:920px){
  #spread-l1,#spread-l2,#spread-l3{grid-template-columns:1fr}
  .page-left{box-shadow:4px 4px 0 var(--accent-soft)}
  .readout{margin-left:0}
}
@media (max-width:520px){
  .backnav{padding:12px 16px 0}
  .site-head{flex-direction:column;align-items:flex-start;padding:8px 16px 14px}
  .tabs,#book{padding-left:16px;padding-right:16px}
  .tab{padding:7px 14px;font-size:12.5px}
  .jarbar{gap:6px}
  .jar{min-width:56px}
  .jar-glass{width:26px;height:72px}
  .jar-name{font-size:9.5px}
}