:root{
  --paper:#F0EFE9; --surface:#FAFAF7; --ink:#17212B; --ink-soft:#5C6A73; --line:#DCDAD2;
  --accent:#0E9E8F; --accent-soft:rgba(14,158,143,.14); --warm:#E2703A; --violet:#7C5CE0;
  --stage:#0F1720; --stage2:#1A2530; --stage-ink:#E9EFF3; --stage-soft:#8FA5B2; --stage-line:#2B3946;
  --serif:"Songti SC","STSong","Noto Serif CJK SC","Source Han Serif SC","SimSun",serif;
  --sans:"PingFang SC","Hiragino Sans GB","Microsoft YaHei","Noto Sans CJK SC","Source Han Sans SC",system-ui,sans-serif;
  box-sizing:border-box; padding-top:env(safe-area-inset-top,0px); padding-bottom:env(safe-area-inset-bottom,0px); color-scheme:light;
}
@media (prefers-color-scheme: dark){ :root:not([data-theme="light"]){
  --paper:#0E1419; --surface:#151D24; --ink:#DEE7EC; --ink-soft:#8CA0AC; --line:#26323A;
  --accent:#35C9B8; --accent-soft:rgba(53,201,184,.16); --warm:#F0955E; --violet:#B6A2FF; color-scheme:dark; } }
:root[data-theme="dark"]{ --paper:#0E1419; --surface:#151D24; --ink:#DEE7EC; --ink-soft:#8CA0AC; --line:#26323A;
  --accent:#35C9B8; --accent-soft:rgba(53,201,184,.16); --warm:#F0955E; --violet:#B6A2FF; color-scheme:dark; }
html{scroll-padding-top:env(safe-area-inset-top,0px)}
*,*::before,*::after{box-sizing:inherit}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--sans);font-size:16px;line-height:1.75;-webkit-font-smoothing:antialiased}
a{color:var(--accent)}
button,input,select{font:inherit;color:inherit}
:focus-visible{outline:2px solid var(--accent);outline-offset:3px}
.wrap{max-width:1240px;margin:0 auto;padding:0 20px 52px}
.topbar{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 20px;padding:20px 0 4px;font-size:.92rem}
.topbar a{text-decoration:none}
.kicker{color:var(--ink-soft);font-weight:700;letter-spacing:.06em}
h1{font-family:var(--serif);font-weight:900;font-size:clamp(1.9rem,4.6vw,3rem);line-height:1.15;margin:.1em 0 0}
h2{font-family:var(--serif);font-weight:900;font-size:1.5rem;line-height:1.3;margin:0 0 8px}
h3{font-size:.98rem;margin:0 0 8px}
.lede{max-width:46em;color:var(--ink-soft);margin:10px 0 18px}
.layout{display:grid;grid-template-columns:minmax(0,1.5fr) minmax(0,1fr);gap:18px;align-items:start}
.stage{position:sticky;top:12px;background:radial-gradient(120% 90% at 30% 15%, var(--stage2), var(--stage) 72%);border:1px solid var(--line);border-radius:6px;overflow:hidden;box-shadow:0 12px 30px -22px rgba(9,16,22,.7)}
.stage canvas{display:block;width:100%;height:min(72vh,680px);touch-action:none;cursor:grab}
.stage canvas:active{cursor:grabbing}
.stage-hint{position:absolute;left:14px;bottom:10px;right:14px;font-size:.8rem;color:var(--stage-soft);pointer-events:none}
.box{background:var(--surface);border:1px solid var(--line);border-radius:5px;padding:14px 16px;margin:0 0 12px}
.chips{display:flex;flex-wrap:wrap;gap:8px}
.chip{border:1px solid var(--line);background:var(--paper);border-radius:999px;padding:5px 14px;cursor:pointer}
.chip[aria-pressed=true]{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.chip i{display:inline-block;width:9px;height:9px;border-radius:50%;margin-right:6px}
.primary{border:0;background:var(--accent);color:#fff;border-radius:999px;padding:8px 20px;font-weight:700;cursor:pointer}
:root[data-theme="dark"] .primary{color:#0C1A1B}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]) .primary{color:#0C1A1B}}
.ghost{border:1.5px solid var(--ink);background:transparent;border-radius:999px;padding:7px 18px;font-weight:700;cursor:pointer}
.row{display:flex;flex-wrap:wrap;align-items:center;gap:10px}
.range{display:grid;grid-template-columns:auto 1fr auto;gap:10px;align-items:center;font-size:.9rem;color:var(--ink-soft)}
.range input{width:100%;accent-color:var(--accent)}
.small{font-size:.86rem;color:var(--ink-soft)}
.big{font-family:var(--serif);font-weight:900;font-size:2.2rem;line-height:1;color:var(--accent);font-variant-numeric:tabular-nums}
dl.ro{display:grid;grid-template-columns:auto 1fr;gap:4px 14px;font-size:.93rem;margin:0}
dl.ro dt{color:var(--ink-soft)} dl.ro dd{margin:0;font-weight:500;font-variant-numeric:tabular-nums}
/* chapter footer */
.chapter-end{margin-top:26px;border-top:1px solid var(--line);padding-top:20px}
.takeaway{font-family:var(--serif);font-weight:900;font-size:1.25rem;line-height:1.5;max-width:30em;margin:0 0 18px}
.quiz{background:var(--surface);border:1px solid var(--line);border-radius:5px;padding:16px;max-width:44em}
.quiz p.q{font-weight:700;margin:0 0 8px}
.quiz .opts{display:flex;flex-direction:column;gap:8px;margin-bottom:6px}
.quiz .opt{text-align:left;border:1px solid var(--line);background:var(--paper);border-radius:6px;padding:8px 12px;cursor:pointer}
.quiz .opt.right{border-color:var(--accent);background:var(--accent-soft)}
.quiz .opt.wrong{border-color:var(--warm);opacity:.75}
.quiz .fb{font-size:.92rem;color:var(--ink-soft);margin:6px 0 16px;min-height:1.2em}
.chapter-nav{display:flex;flex-wrap:wrap;justify-content:space-between;gap:10px;margin-top:20px}
.chapter-nav a{text-decoration:none;border-radius:999px;padding:8px 18px;font-weight:700;border:1.5px solid var(--ink);color:var(--ink)}
.chapter-nav a.next{background:var(--ink);color:var(--paper)}
footer.fine{margin-top:26px;font-size:.85rem;color:var(--ink-soft);max-width:58em}
@media (max-width:900px){ .layout{grid-template-columns:1fr} .stage{position:relative;top:0} .stage canvas{height:56vh} }
/* ---- 评价与留言 ---- */
.fbk{margin-top:22px}
.fb-hp,.fb-hp2{position:absolute;left:-9999px;width:1px;height:1px;opacity:0}
.fb-rate .fb-more{margin-top:10px}
.fbk textarea,.fb input[type=text],.fb .fb-nick,.fb .fb-body{width:100%;border:1px solid var(--line);border-radius:6px;background:var(--paper);color:var(--ink);padding:8px 10px;margin-bottom:8px;resize:vertical}
.fbk .fb-nick{max-width:220px}
.fb-item{border-top:1px solid var(--line);padding:10px 0}
.fb-item:first-child{border-top:0}
.fb-head{display:flex;align-items:baseline;gap:10px}
.fb-item p{margin:4px 0 0;white-space:pre-wrap;overflow-wrap:anywhere}
.fb-reply{margin-top:8px;padding:8px 12px;border-left:3px solid var(--accent);background:var(--accent-soft);border-radius:0 6px 6px 0}
.fb-reply b{font-size:.85rem;color:var(--accent)}
.fb-list{margin-bottom:14px}