:root{
  --ink:#1e2433; --muted:#6b7280; --line:#e5e7eb;
  --c0:#e11d74; --c0s:#fff0f6;
  --c1:#2563eb; --c1s:#eef4ff;
  --c2:#0e9f8e; --c2s:#ecfdf8;
  --c3:#e07a00; --c3s:#fff6e8;
  --c4:#7c3aed; --c4s:#f4efff;
  --hl:#fde68a;
}
*{box-sizing:border-box}
html,body{margin:0;height:100%;background:#0b1020;overflow:hidden;
  font-family:"PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;color:var(--ink)}
#stage{position:absolute;width:1600px;height:900px;transform-origin:0 0;background:#fff;overflow:hidden;
  box-shadow:0 30px 80px rgba(0,0,0,.5)}

/* ---------- slide ---------- */
.slide{position:absolute;inset:0;display:none;font-size:34px;line-height:1.6;--c:var(--c0);--cs:var(--c0s);
  background:linear-gradient(160deg,#fff 60%,var(--cs))}
.slide.on{display:block;animation:slideIn .45s ease}
@keyframes slideIn{from{opacity:0;transform:translateX(30px)}to{opacity:1;transform:none}}
.slide[data-p="1"]{--c:var(--c1);--cs:var(--c1s)}
.slide[data-p="2"]{--c:var(--c2);--cs:var(--c2s)}
.slide[data-p="3"]{--c:var(--c3);--cs:var(--c3s)}
.slide[data-p="4"]{--c:var(--c4);--cs:var(--c4s)}
.slide .inner{position:absolute;left:90px;right:90px;top:70px;transform-origin:0 0}
.slide .kicker{position:absolute;top:24px;left:90px;font-size:22px;font-weight:700;color:var(--c);letter-spacing:2px}
.slide .kicker::before{content:"";display:inline-block;width:12px;height:12px;border-radius:50%;background:var(--c);margin-right:10px;vertical-align:middle}
aside.note{display:none}

/* ---------- full-bleed picture slides ---------- */
.slide.pic{background:#000;color:#fff}
.slide.pic .bg{position:absolute;inset:0;background-size:cover;background-position:center;animation:kenburns 18s ease-out both}
@keyframes kenburns{from{transform:scale(1.12)}to{transform:scale(1)}}
.slide.pic .shade{position:absolute;inset:0}
.slide.pic .inner{top:auto;bottom:90px}
.slide.pic.left .shade{background:linear-gradient(90deg,rgba(8,12,30,.82) 0%,rgba(8,12,30,.55) 42%,rgba(8,12,30,0) 70%)}
.slide.pic.right .shade{background:linear-gradient(270deg,rgba(8,12,30,.82) 0%,rgba(8,12,30,.55) 42%,rgba(8,12,30,0) 70%)}
.slide.pic.right .inner{left:auto;width:720px;right:80px}
.slide.pic.bottom .shade{background:linear-gradient(0deg,rgba(8,12,30,.88) 0%,rgba(8,12,30,.5) 38%,rgba(8,12,30,0) 62%)}
.slide.pic .chap{display:inline-block;font-size:26px;font-weight:700;letter-spacing:4px;padding:4px 18px;border-radius:999px;background:var(--c);margin-bottom:18px}
.slide.pic h1{font-size:92px;line-height:1.15;margin:0 0 18px;text-shadow:0 4px 24px rgba(0,0,0,.5)}
.slide.pic p{font-size:36px;margin:0;max-width:760px;text-shadow:0 2px 12px rgba(0,0,0,.6)}
.slide.pic .left-box{max-width:760px}

/* ---------- typography ---------- */
h1{font-size:84px;margin:0 0 20px;line-height:1.2}
h2{font-size:56px;margin:0 0 30px;line-height:1.25}
h2 small{font-size:28px;color:var(--muted);font-weight:400;margin-left:16px}
p{margin:0 0 14px}
.muted{color:var(--muted)} .small{font-size:26px}
.m,.q,.steps,.mathy{font-family:"Times New Roman","Songti SC","STSong",serif}
.q{font-size:44px;font-weight:600;background:var(--cs);border-radius:18px;padding:16px 30px;margin:0 0 26px;display:inline-block}
.fr{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;font-size:.72em;line-height:1.12;margin:0 3px}
.fr>span:first-child{border-bottom:2px solid currentColor;padding:0 3px}
.steps p{margin:0 0 6px;font-size:40px}
.steps em{font-style:normal;font-family:"PingFang SC","Microsoft YaHei",sans-serif;font-size:26px;color:var(--c);background:var(--cs);border-radius:8px;padding:2px 12px;margin-left:18px;vertical-align:middle}
.hl{background:var(--hl);border-radius:6px;padding:0 4px}
.ca{color:var(--c0);font-weight:700}.cb{color:var(--c1);font-weight:700}.cc{color:var(--c);font-weight:700}
.big-say{font-size:48px;font-weight:700;line-height:1.45}
.tag{display:inline-block;background:var(--c);color:#fff;border-radius:10px;padding:0 14px;font-size:.78em;margin-right:10px}

/* ---------- fragments ---------- */
.f{transition:opacity .35s,transform .35s}
.f:not(.on){opacity:0;transform:translateY(10px);pointer-events:none}
.f.ghost{display:none}
.f.cancel:not(.on){opacity:1;transform:none}
.f.cancel{position:relative;transition:color .3s}
.f.cancel.on{color:#b8bec9}
.f.cancel::after{content:"";position:absolute;left:-4px;right:-4px;top:52%;height:4px;background:#ef4444;border-radius:2px;transform:scaleX(0);transform-origin:left;transition:transform .35s}
.f.cancel.on::after{transform:scaleX(1)}

/* ---------- layout bits ---------- */
.cols{display:grid;grid-template-columns:1fr 1fr;gap:40px;align-items:start}
.cols3{display:grid;grid-template-columns:repeat(3,1fr);gap:26px}
.box{background:var(--cs);border-radius:22px;padding:24px 30px}
.box b.t{display:block;font-size:40px;color:var(--c);margin-bottom:6px}
.card{background:#fff;border:2px solid var(--line);border-radius:22px;padding:22px 28px;box-shadow:0 8px 24px rgba(30,36,51,.06)}
.emoji{font-size:64px;line-height:1;display:block;margin-bottom:10px}
button.ui,select.ui,input.ui{font:inherit;font-size:28px;border:2px solid var(--ink);background:#fff;border-radius:14px;padding:6px 20px;cursor:pointer}
button.ui.pri{background:var(--ink);color:#fff}
button.ui:active{transform:scale(.97)}
input.ui{width:150px;cursor:text}
.timer{font-size:120px;font-weight:800;font-variant-numeric:tabular-nums;font-family:system-ui,sans-serif;color:var(--c)}
svg text{font-family:"Times New Roman","Songti SC",serif}

/* ---------- rule machine ---------- */
.machine{display:grid;grid-template-columns:520px 1fr;gap:40px}
.mscreen{background:#101828;color:#e5e7eb;border-radius:24px;padding:26px 34px;min-height:430px;font-size:40px;font-family:"Times New Roman",serif;
  box-shadow:inset 0 0 0 3px #24304a,0 20px 40px rgba(16,24,40,.25)}
.mscreen .rule{color:#f9a8d4;font-size:30px;margin-bottom:10px}
.mscreen .ln{opacity:0;transform:translateX(-10px);transition:all .35s}
.mscreen .ln.show{opacity:1;transform:none}
.mscreen .A{color:#ff7ab6;font-weight:700;display:inline-block;animation:pop .5s}
.mscreen .B{color:#7cb3ff;font-weight:700;display:inline-block;animation:pop .5s}
.mscreen .R{color:#fde047;font-weight:800;font-size:1.2em}
@keyframes pop{0%{transform:scale(.2) translateY(-40px);opacity:0}70%{transform:scale(1.25)}100%{transform:none;opacity:1}}
.balls{display:flex;gap:26px;align-items:center;margin:8px 0 18px}
.ball{width:120px;height:120px;border-radius:50%;display:grid;place-items:center;font-size:44px;font-weight:800;color:#fff;
  font-family:system-ui,sans-serif;box-shadow:inset -10px -12px 0 rgba(0,0,0,.15),0 10px 20px rgba(0,0,0,.15)}
.ball.a{background:radial-gradient(circle at 35% 30%,#ff9cc8,#e11d74)}
.ball.b{background:radial-gradient(circle at 35% 30%,#9cc4ff,#2563eb)}
.ball input{width:96px;background:transparent;border:0;color:#fff;font:inherit;text-align:center;outline:none}
.stamp{display:inline-block;font-size:64px;font-weight:900;color:#ef4444;border:6px solid #ef4444;border-radius:16px;padding:0 20px;transform:rotate(-8deg);animation:stamp .4s}
@keyframes stamp{from{transform:scale(2.4) rotate(-8deg);opacity:0}to{transform:scale(1) rotate(-8deg);opacity:1}}

/* ---------- chips (凑整) ---------- */
.chips{position:relative;height:330px}
.chip{position:absolute;top:0;padding:10px 26px;border-radius:999px;font-size:52px;font-weight:700;font-family:"Times New Roman",serif;
  transition:all .7s cubic-bezier(.6,-.2,.3,1.3);box-shadow:0 8px 20px rgba(0,0,0,.08);white-space:nowrap}
.chip.p{background:#fff0f6;color:#be185d;border:3px solid #f9a8d4}
.chip.n{background:#eef4ff;color:#1d4ed8;border:3px solid #93c5fd}
.chip.r{background:#fef3c7;color:#92400e;border:3px solid #fbbf24}
.chip.gone{opacity:0;transform:scale(.6)}

/* ---------- digit grid ---------- */
.dgrid{display:grid;grid-template-columns:repeat(4,110px);gap:10px;font-family:"Times New Roman",serif;font-size:72px;font-weight:700}
.dgrid div{height:110px;display:grid;place-items:center;border-radius:16px;background:#f3f4f6;transition:all .4s}
.dgrid div.lit{background:var(--c);color:#fff;transform:translateY(-6px)}
.dsum{display:grid;grid-template-columns:repeat(4,110px);gap:10px;margin-top:14px;font-size:40px;text-align:center;color:var(--c);font-weight:700}
.dsum span{opacity:0;transition:opacity .4s}.dsum span.show{opacity:1}

/* ---------- see→think table ---------- */
table.look{border-collapse:collapse;width:100%;font-size:29px}
table.look td{padding:11px 16px;border-bottom:2px solid var(--line);vertical-align:middle}
table.look td:first-child{font-weight:700;width:44%}
table.look td.arrow{width:50px;color:var(--muted);text-align:center}
table.look tr.f td:first-child{color:var(--c)}

/* ---------- chrome ---------- */
#bar{position:fixed;left:0;right:0;bottom:0;height:5px;background:#1f2937;z-index:5}
#bar i{display:block;height:100%;width:0;background:linear-gradient(90deg,#e11d74,#2563eb,#0e9f8e,#e07a00,#7c3aed);transition:width .3s}
#num{position:fixed;right:16px;bottom:12px;color:#9ca3af;font:14px system-ui,sans-serif;z-index:5}
#navL,#navR{position:fixed;bottom:28px;z-index:6;width:56px;height:56px;border-radius:50%;border:0;background:rgba(17,24,39,.25);color:#fff;font-size:30px;cursor:pointer;opacity:.35;transition:all .2s}
#navL:hover,#navR:hover{opacity:1;background:rgba(17,24,39,.75)}
#navL{right:96px}#navR{right:28px}
#notebox{position:fixed;left:0;right:0;bottom:0;max-height:34vh;overflow:auto;background:#fffbeb;border-top:3px solid #f59e0b;padding:12px 22px 22px;font-size:18px;line-height:1.6;display:none;z-index:7}
#notebox.on{display:block}
#ov{position:fixed;inset:0;background:rgba(11,16,32,.97);z-index:9;display:none;overflow:auto;padding:30px}
#ov.on{display:block}
#ov h3{color:#fff;font:600 20px system-ui,sans-serif;margin:16px 0 8px}
#ov .g{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:10px}
#ov button{text-align:left;background:#1f2937;color:#e5e7eb;border:1px solid #374151;border-radius:10px;padding:10px 12px;font:15px system-ui,sans-serif;cursor:pointer}
#ov button.cur{border-color:#f472b6;background:#3b1d33}
#ov button span{color:#9ca3af;margin-right:6px}
#hint{position:fixed;left:16px;bottom:12px;color:#6b7280;font:13px system-ui,sans-serif;z-index:5;transition:opacity 1s}

@media print{
  html,body{overflow:visible;background:#fff;height:auto}
  #stage{position:static;transform:none!important;box-shadow:none}
  .slide{display:block!important;position:relative;width:1600px;height:900px;page-break-after:always;zoom:.5;animation:none}
  .f{opacity:1!important;transform:none!important}
  #bar,#num,#hint,#notebox,#ov,#navL,#navR{display:none!important}
}

/* ---------- cakes ---------- */
.cakes{display:flex;flex-direction:column;gap:8px}
.crow{display:flex;gap:8px;align-items:center}
.crow .who{width:40px;height:40px;border-radius:50%;color:#fff;font:700 22px system-ui,sans-serif;display:grid;place-items:center;margin-right:8px}
.crow i{width:44px;height:36px;border-radius:8px;opacity:.85}

/* ---------- L-square ---------- */
#lsq .cell{position:absolute;width:42px;height:42px;border-radius:6px;background:#a7f3d0;border:2px solid #0e9f8e;transition:all .9s cubic-bezier(.5,-.2,.3,1.2)}
#lsq .cell.dim{opacity:.25}
#lsq .cell.hot{background:#fbbf24;border-color:#b45309}