/* ============================================================
   统一场论 · 场与手稿  FIELD & MANUSCRIPT
   设计语言：墨宇（深空墨黑）× 雕版纸（手稿米白）× 朱砂/石青/鎏金
   母题：圆柱状螺旋 —— 导航、进度、背景场、图表共用同一几何
   ============================================================ */

/* ---------- 1. 令牌 ---------- */
:root{
  --ink:#070a0f;
  --ink-2:#0b0f16;
  --ink-3:#111823;
  --ink-4:#18222f;
  --paper:#efe6d2;
  --paper-2:#e2d6bd;
  --paper-ink:#241f18;
  --paper-dim:#6a5f4d;

  --gold:#d9b45b;
  --gold-deep:#a07d2c;
  --cinnabar:#d0563a;
  --cinnabar-deep:#8e3320;
  --jade:#54a8b8;
  --jade-deep:#2c6d7a;
  --violet:#8f7ac0;

  --text:#d6dde7;
  --text-dim:#8a94a4;
  --text-faint:#5d6675;
  --hair:rgba(217,180,91,.18);
  --hair-soft:rgba(214,222,235,.10);

  --serif:"Songti SC","Noto Serif SC","Source Han Serif SC","Source Han Serif CN",STSong,SimSun,"Times New Roman",serif;
  --sans:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans SC",system-ui,sans-serif;
  --mono:"SFMono-Regular",Consolas,"Cascadia Mono","JetBrains Mono","Liberation Mono",monospace;

  --rail:88px;
  --maxw:1140px;
  --ease:cubic-bezier(.22,.61,.36,1);
}

*,*::before,*::after{box-sizing:border-box}
[hidden]{display:none !important}

html{
  -webkit-text-size-adjust:100%;
  scroll-behavior:smooth;
  background:var(--ink);
}
html.static,html.static *{scroll-behavior:auto !important}

body{
  margin:0;
  font-family:var(--sans);
  font-size:16px;
  line-height:1.85;
  color:var(--text);
  background:var(--ink);
  overflow-x:clip;
  letter-spacing:.01em;
  text-rendering:optimizeLegibility;
  -webkit-font-smoothing:antialiased;
}

::selection{background:rgba(217,180,91,.28);color:#fff}

/* ---------- 2. 背景场画布 + 颗粒 ---------- */
#field{
  position:fixed;inset:0;width:100%;height:100%;
  z-index:0;display:block;
  pointer-events:none;
}
.vignette{
  position:fixed;inset:0;z-index:1;pointer-events:none;
  background:
    radial-gradient(120% 90% at 50% -10%, rgba(84,168,184,.10), transparent 55%),
    radial-gradient(90% 70% at 50% 110%, rgba(208,86,58,.07), transparent 60%),
    radial-gradient(140% 120% at 50% 50%, transparent 40%, rgba(3,5,8,.72) 100%);
}
.grain{
  position:fixed;inset:-50%;z-index:2;pointer-events:none;opacity:.045;
  background-image:url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='180' height='180'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='.85' numOctaves='3'/></filter><rect width='180' height='180' filter='url(%23n)'/></svg>");
  animation:grainshift 8s steps(6) infinite;
}
@keyframes grainshift{
  0%{transform:translate(0,0)} 20%{transform:translate(-3%,2%)} 40%{transform:translate(2%,-3%)}
  60%{transform:translate(-2%,-2%)} 80%{transform:translate(3%,1%)} 100%{transform:translate(0,0)}
}

/* ---------- 3. 竖排螺旋导轨（桌面） ---------- */
.rail{
  position:fixed;left:0;top:0;bottom:0;width:var(--rail);z-index:40;
  display:flex;flex-direction:column;align-items:center;
  padding:18px 0 14px;
  border-right:1px solid var(--hair);
  background:linear-gradient(180deg,rgba(7,10,15,.92),rgba(7,10,15,.62) 40%,rgba(7,10,15,.92));
  backdrop-filter:blur(3px);
}
.seal{
  width:40px;height:40px;flex:none;position:relative;
  display:grid;place-items:center;
  background:linear-gradient(150deg,var(--cinnabar),var(--cinnabar-deep));
  color:#fff5ea;font-family:var(--serif);font-size:22px;font-weight:700;
  border-radius:3px;transform:rotate(-4deg);
  box-shadow:0 0 0 1px rgba(255,255,255,.18) inset, 0 6px 22px rgba(208,86,58,.34);
  cursor:pointer;transition:transform .5s var(--ease);
}
.seal:hover{transform:rotate(4deg) scale(1.06)}
.seal::after{
  content:"";position:absolute;inset:3px;border:1px solid rgba(255,255,255,.34);border-radius:2px;
}
.rail-helix{flex:1;width:100%;min-height:0;margin:14px 0}
.rail-helix svg{width:100%;height:100%;display:block;overflow:visible}
.rail-helix .turn{pointer-events:none}
.rail-helix .turn line{stroke:rgba(214,222,235,.30);transition:stroke .45s var(--ease)}
.rail-helix .turn-hit{fill:none;stroke:transparent;stroke-width:18;pointer-events:stroke;cursor:pointer}
.rail-helix .turn-hit:hover + .turn line{stroke:rgba(217,180,91,.85)}
.rail-helix .turn.on line{stroke:var(--gold)}
.rail-helix .bead{fill:#fff;filter:drop-shadow(0 0 6px rgba(217,180,91,.9))}
.rail-idx{
  font-family:var(--mono);font-size:9px;letter-spacing:.16em;color:var(--text-faint);
  writing-mode:vertical-rl;text-orientation:mixed;margin-top:6px;
}

/* ---------- 4. 主内容壳 ---------- */
.shell{position:relative;z-index:10;padding-left:var(--rail)}
main{max-width:var(--maxw);margin:0 auto;padding:0 34px}
section.ch{padding:96px 0 84px;position:relative;overflow-x:clip}
section.ch + section.ch{border-top:1px solid var(--hair-soft)}

/* ---------- 5. 章节标题系统 ---------- */
.ch-head{position:relative;display:grid;grid-template-columns:64px 1fr;gap:26px;align-items:start;margin-bottom:46px}
.ch-num{
  font-family:var(--serif);font-size:44px;line-height:1.05;text-align:center;
  color:transparent;-webkit-text-stroke:1px rgba(217,180,91,.55);
  writing-mode:vertical-rl;text-orientation:upright;margin-top:4px;
  user-select:none;
}
.ch-num::first-line{color:transparent}
.ch-kicker{
  font-family:var(--mono);font-size:11px;letter-spacing:.34em;text-transform:uppercase;
  color:var(--gold);margin:0 0 10px;
}
.ch-kicker::before{content:"";display:inline-block;width:26px;height:1px;background:var(--gold);vertical-align:middle;margin-right:12px;opacity:.7}
h1.ch-title,h2.ch-title{
  font-family:var(--serif);font-weight:600;letter-spacing:.05em;
  margin:0 0 12px;line-height:1.22;color:#f2f5f9;
}
h2.ch-title{font-size:clamp(27px,4.2vw,42px)}
.ch-sub{margin:0;color:var(--text-dim);font-size:15.5px;max-width:64ch}
.ch-sub em{color:var(--gold);font-style:normal}

h3{font-family:var(--serif);font-weight:600;letter-spacing:.04em;color:#eaf0f7;font-size:20px;margin:38px 0 14px}
h4{font-family:var(--sans);font-weight:600;color:var(--gold);font-size:13px;letter-spacing:.16em;margin:26px 0 10px;text-transform:uppercase}
p{margin:0 0 16px}
a{color:var(--jade);text-decoration:none;border-bottom:1px solid rgba(84,168,184,.32);transition:.3s var(--ease)}
a:hover{color:#8fd8e6;border-color:#8fd8e6}
strong{color:#fff;font-weight:600}
small{font-size:12.5px;color:var(--text-faint)}

.lead{font-size:18.5px;line-height:1.95;color:#e4eaf2}
.lead::first-letter{
  font-family:var(--serif);font-size:2.9em;float:left;line-height:.86;
  padding:6px 12px 0 0;color:var(--gold);
}
.dim{color:var(--text-dim)}
.gold{color:var(--gold)}
.jade{color:var(--jade)}
.cin{color:var(--cinnabar)}
.num{font-family:var(--mono);font-variant-numeric:tabular-nums}

/* 术语虚线 */
.term{border-bottom:1px dotted var(--gold);cursor:help;position:relative;color:#f0e3c4}

/* ---------- 6. 通用面板 ---------- */
.plate{
  position:relative;background:linear-gradient(165deg,rgba(17,24,35,.92),rgba(11,15,22,.86));
  border:1px solid var(--hair-soft);border-radius:2px;padding:26px 28px;
  box-shadow:0 24px 60px -30px rgba(0,0,0,.9);
}
.plate::before{
  content:"";position:absolute;left:0;top:14px;bottom:14px;width:2px;
  background:linear-gradient(180deg,transparent,var(--gold),transparent);opacity:.5;
}
.grid{display:grid;gap:20px}
.g2{grid-template-columns:repeat(2,minmax(0,1fr))}
.g3{grid-template-columns:repeat(3,minmax(0,1fr))}
.g4{grid-template-columns:repeat(4,minmax(0,1fr))}

/* 纸版（手稿层） */
.paper{
  background:
    linear-gradient(180deg,rgba(255,255,255,.5),transparent 30%),
    repeating-linear-gradient(0deg,rgba(120,100,60,.045) 0 1px,transparent 1px 4px),
    var(--paper);
  color:var(--paper-ink);
  border:1px solid #c9b98f;border-radius:2px;padding:24px 26px;position:relative;
  box-shadow:0 18px 44px -22px rgba(0,0,0,.85), inset 0 0 40px rgba(160,125,44,.10);
  font-family:var(--serif);line-height:1.95;
}
.paper h3,.paper h4{color:#3b3225}
.paper::after{
  content:"";position:absolute;right:14px;bottom:12px;width:34px;height:34px;border-radius:50%;
  border:1.5px dashed rgba(142,51,32,.34);
}
.paper .stamp{
  position:absolute;top:12px;right:12px;font-family:var(--mono);font-size:9.5px;letter-spacing:.18em;
  color:#8e3320;border:1px solid rgba(142,51,32,.5);padding:2px 7px;border-radius:2px;
  transform:rotate(2deg);
}

/* ---------- 7. 标签 / 徽章 ---------- */
.tag{
  display:inline-flex;align-items:center;gap:6px;
  font-family:var(--mono);font-size:10.5px;letter-spacing:.12em;
  padding:3px 9px;border-radius:2px;border:1px solid currentColor;line-height:1.5;
  white-space:nowrap;
}
.t-claim{color:var(--cinnabar);background:rgba(208,86,58,.10)}
.t-main{color:var(--jade);background:rgba(84,168,184,.10)}
.t-open{color:var(--gold);background:rgba(217,180,91,.10)}
.t-warn{color:#e07a5f;background:rgba(224,122,95,.10)}
.t-grey{color:var(--text-dim)}

/* ---------- 8. 雕版数学排版 ---------- */
.eq{
  font-family:var(--serif);font-size:19px;line-height:2.1;
  color:#f4ecda;letter-spacing:.01em;
  display:flex;align-items:center;justify-content:center;gap:.3em;
  padding:18px 12px;margin:16px 0;
  background:radial-gradient(120% 140% at 50% 0%,rgba(217,180,91,.07),transparent 70%);
  border-top:1px solid var(--hair);border-bottom:1px solid var(--hair);
  text-align:center;flex-wrap:wrap;
}
.eq .lbl{
  font-family:var(--mono);font-size:10px;letter-spacing:.14em;color:var(--text-faint);
  margin-left:auto;align-self:flex-end;
}
.eq.sm{font-size:16.5px;padding:12px 8px}
.mv{font-style:italic;font-weight:600;font-family:var(--serif)}
.mo{font-style:normal;font-weight:400}
.frac{display:inline-flex;flex-direction:column;text-align:center;vertical-align:middle;margin:0 .22em;font-size:.94em;line-height:1.28}
.frac>.n{border-bottom:1px solid currentColor;padding:0 .3em .06em}
.frac>.d{padding:.06em .3em 0}
.sq{display:inline-flex;align-items:flex-start;margin:0 .1em}
.sq>.rad{font-size:1.06em;line-height:1;transform:scaleY(1.18) translateY(.02em)}
.sq>.body{border-top:1px solid currentColor;padding:.08em .18em 0 .06em;margin-top:.16em}
sub,sup{font-size:.66em;line-height:0;font-family:var(--mono)}
sub{vertical-align:-.28em}
sup{vertical-align:.52em}
.op{margin:0 .3em;color:#e8dcc0}
.paren{font-size:1.25em;vertical-align:-.12em;color:#cbbd99}

/* ---------- 9. 图像版 ---------- */
.fig{margin:0;position:relative;background:var(--ink-2);border:1px solid var(--hair-soft);overflow:hidden}
.fig img{display:block;width:100%;height:auto;opacity:0;transform:scale(1.04);transition:opacity 1.1s var(--ease),transform 1.4s var(--ease)}
.fig img.show{opacity:1;transform:none}
.fig figcaption{
  font-family:var(--mono);font-size:11px;line-height:1.7;color:var(--text-faint);
  padding:10px 14px;border-top:1px solid var(--hair-soft);background:rgba(7,10,15,.6);
}
.fig figcaption b{color:var(--gold);font-weight:400;letter-spacing:.1em}
.fig .src{color:#4d5665}
.fig--paper{background:var(--paper);border-color:#c9b98f}
.fig--paper figcaption{background:#e6dbc0;color:#6a5f4d;border-top-color:#c9b98f}
.fig--paper figcaption b{color:#8e3320}

/* ---------- 10. 数据表 ---------- */
.tbl{width:100%;border-collapse:collapse;font-size:14px;margin:18px 0}
.tbl th,.tbl td{padding:11px 12px;text-align:left;border-bottom:1px solid var(--hair-soft);vertical-align:top}
.tbl thead th{
  font-family:var(--mono);font-size:10.5px;letter-spacing:.14em;color:var(--gold);
  border-bottom:1px solid var(--hair);text-transform:uppercase;white-space:nowrap;
}
.tbl tbody tr{transition:background .3s}
.tbl tbody tr:hover{background:rgba(217,180,91,.05)}
.tbl td.k{color:#e9e2cf;font-family:var(--serif);font-size:15px}
.tbl .v{font-family:var(--mono);color:var(--jade);white-space:nowrap;font-size:13px}
.tbl-wrap{overflow-x:auto;-webkit-overflow-scrolling:touch}

/* ---------- 11. 对照（双栏） ---------- */
.vs{display:grid;grid-template-columns:1fr 1fr;gap:0;border:1px solid var(--hair-soft)}
.vs>div{padding:20px 22px}
.vs .a{background:rgba(208,86,58,.055);border-right:1px solid var(--hair-soft)}
.vs .b{background:rgba(84,168,184,.055)}
.vs h4{margin-top:0}
.vs .a h4{color:var(--cinnabar)}
.vs .b h4{color:var(--jade)}
@media (max-width:760px){.vs{grid-template-columns:1fr}.vs .a{border-right:0;border-bottom:1px solid var(--hair-soft)}}

/* ---------- 12. 揭示动画 ---------- */
.rv{opacity:0;transform:translateY(26px)}
.rv.on{opacity:1;transform:none;transition:opacity .95s var(--ease),transform .95s var(--ease)}
html.static .rv{opacity:1 !important;transform:none !important;transition:none !important}
html.no-io .rv{opacity:1;transform:none}

/* ---------- 13. 移动端导轨 ---------- */
.orbit{display:none}

/* ---------- 14. 页脚 ---------- */
footer{
  position:relative;z-index:10;padding:56px 0 72px;border-top:1px solid var(--hair);
  background:linear-gradient(180deg,transparent,rgba(3,5,8,.85));
}
footer .fine{font-family:var(--mono);font-size:11px;color:var(--text-faint);line-height:2}

/* ---------- 15. 响应式 ---------- */
@media (max-width:980px){
  :root{--rail:0px}
  .rail{display:none}
  .shell{padding-left:0}
  main{padding:0 20px}
  section.ch{padding:64px 0 56px}
  .ch-head{grid-template-columns:44px 1fr;gap:14px;margin-bottom:30px}
  .ch-num{font-size:30px}
  .g3,.g4{grid-template-columns:repeat(2,minmax(0,1fr))}
  .lead{font-size:16.5px}
  body{font-size:15.5px;line-height:1.9}
  .eq{font-size:17px}
}
@media (max-width:600px){
  .g2,.g3,.g4{grid-template-columns:1fr}
  .plate{padding:20px 18px}
  .paper{padding:20px 18px}
  body{padding-bottom:64px}
}

/* ---------- 16. 无障碍 / 减弱动效 ---------- */
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .grain{animation:none}
  .rv{opacity:1;transform:none}
  *{transition-duration:.01ms !important;animation-duration:.01ms !important}
}
:focus-visible{outline:1px solid var(--gold);outline-offset:3px}
.skip{position:absolute;left:-9999px;top:0;z-index:99;background:var(--gold);color:#000;padding:8px 14px}
.skip:focus{left:8px;top:8px}