:root{--ink: #102a2c;--ink-soft: #3d5a5c;--paper: #f3f7f6;--paper-2: #e7efed;--teal: #0f766e;--teal-deep: #115e59;--accent: #c45c26;--line: rgba(16, 42, 44, .1);--ok: #15803d;--shadow: 0 18px 50px rgba(16, 42, 44, .08);--radius: 18px;--font-display: "Outfit", "Noto Sans SC", sans-serif;--font-body: "Noto Sans SC", "Outfit", sans-serif}*{box-sizing:border-box}html,body,#app{min-height:100%}body{margin:0;color:var(--ink);font-family:var(--font-body);background:radial-gradient(1200px 500px at 10% -10%,rgba(15,118,110,.16),transparent 60%),radial-gradient(900px 420px at 90% 0%,rgba(196,92,38,.1),transparent 55%),linear-gradient(180deg,#f7fbfa 0%,var(--paper) 40%,#eef4f2 100%);-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button,input,textarea,select{font:inherit}button{cursor:pointer}.shell{width:min(1080px,calc(100% - 32px));margin:0 auto}.app-root{min-height:100vh;display:flex;flex-direction:column}main{flex:1}.site-header{position:sticky;top:0;z-index:20;-webkit-backdrop-filter:blur(14px);backdrop-filter:blur(14px);background:#f7fbfad1;border-bottom:1px solid var(--line)}.site-header-inner{display:flex;align-items:center;justify-content:space-between;gap:1rem;padding:.9rem 0}.brand{display:flex;align-items:center;gap:.75rem}.brand-mark{width:2.2rem;height:2.2rem;border-radius:.7rem;background:linear-gradient(140deg,var(--teal),#2dd4bf 55%,var(--accent));box-shadow:0 8px 20px #0f766e47}.brand-name{font-family:var(--font-display);font-weight:700;letter-spacing:.02em}.nav-actions{display:flex;flex-wrap:wrap;gap:.5rem;justify-content:flex-end}.btn{display:inline-flex;align-items:center;justify-content:center;border-radius:999px;padding:.55rem 1rem;border:1px solid transparent;transition:transform .15s ease,background .15s ease,border-color .15s ease}.btn:hover{transform:translateY(-1px)}.btn-primary{background:var(--teal);color:#fff}.btn-primary:hover{background:var(--teal-deep)}.btn-ghost{background:transparent;border-color:var(--line);color:var(--ink)}.btn-ghost:hover{background:#0f766e0f}.btn-accent{background:var(--accent);color:#fff}.site-footer{border-top:1px solid var(--line);margin-top:3rem;color:var(--ink-soft);font-size:.88rem}.site-footer-inner{display:flex;flex-wrap:wrap;gap:.75rem 1.25rem;justify-content:space-between;padding:1.25rem 0 1.75rem}.footer-links{display:flex;flex-wrap:wrap;gap:.85rem}.footer-links a:hover{color:var(--teal)}.hero{padding:3.2rem 0 2rem}.hero-brand{font-family:var(--font-display);font-size:clamp(2.4rem,6vw,3.6rem);font-weight:700;line-height:1.08;letter-spacing:-.02em;margin:0 0 .85rem;background:linear-gradient(120deg,var(--teal-deep),var(--teal) 45%,#0f766e 70%,var(--accent));-webkit-background-clip:text;background-clip:text;color:transparent}.hero-lead{max-width:36rem;margin:0 0 1.6rem;color:var(--ink-soft);font-size:1.05rem;line-height:1.7}.search-bar{display:flex;gap:.6rem;max-width:40rem;margin-bottom:1.5rem}.search-bar input{flex:1;border:1px solid var(--line);background:#ffffffc7;border-radius:999px;padding:.85rem 1.15rem;outline:none;box-shadow:var(--shadow)}.search-bar input:focus{border-color:#0f766e73}.stats-row{display:flex;flex-wrap:wrap;gap:1rem 1.5rem;color:var(--ink-soft);font-size:.92rem}.stats-row strong{color:var(--teal-deep);font-family:var(--font-display)}.industry-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(160px,1fr));gap:.85rem;margin:2rem 0 1rem}.industry-tile{text-align:left;border:1px solid var(--line);background:#ffffff8c;border-radius:var(--radius);padding:1rem 1.05rem;transition:border-color .15s ease,transform .15s ease,box-shadow .15s ease}.industry-tile:hover:not(:disabled){border-color:#0f766e59;transform:translateY(-2px);box-shadow:var(--shadow)}.industry-tile:disabled{opacity:.55;cursor:not-allowed}.industry-tile .icon{font-size:1.35rem;margin-bottom:.35rem}.industry-tile .name{font-weight:600}.industry-tile .hint{margin-top:.25rem;font-size:.78rem;color:var(--ink-soft)}.section-title{font-family:var(--font-display);font-size:1.35rem;margin:2.2rem 0 .85rem}.hot-list{display:grid;gap:.65rem}.q-row{display:block;padding:1rem 1.1rem;border-radius:14px;border:1px solid transparent;background:#ffffff7a;transition:background .15s ease,border-color .15s ease,transform .15s ease}.q-row:hover{background:#ffffffe6;border-color:#0f766e33;transform:translate(2px)}.q-title{font-weight:600;margin-bottom:.35rem}.q-preview{color:var(--ink-soft);font-size:.92rem;line-height:1.55}.q-meta{display:flex;flex-wrap:wrap;gap:.4rem;margin-top:.55rem}.chip{display:inline-flex;align-items:center;border-radius:999px;padding:.15rem .55rem;font-size:.75rem;background:#0f766e14;color:var(--teal-deep)}.chip.muted{background:#102a2c0f;color:var(--ink-soft)}.browse-layout{display:grid;grid-template-columns:220px 1fr;gap:1.5rem;padding:1.75rem 0 2.5rem;align-items:start}.side-panel{position:sticky;top:5rem;align-self:start;padding-right:.5rem;max-height:calc(100vh - 6rem);overflow-y:auto;overscroll-behavior:contain;scrollbar-gutter:stable}.browse-main{min-width:0}.side-label{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--ink-soft);margin:0 0 .55rem}.topic-list{display:grid;gap:.35rem;margin-bottom:1.25rem}.topic-group{display:grid;gap:.15rem}.topic-btn{display:flex;align-items:center;gap:.35rem;width:100%;text-align:left;border:0;background:transparent;padding:.45rem .6rem;border-radius:10px;color:var(--ink-soft)}.topic-btn.active,.topic-btn:hover{background:#0f766e1a;color:var(--teal-deep)}.topic-btn-parent .topic-name{flex:1}.topic-caret{display:inline-flex;width:.85rem;justify-content:center;font-size:.72rem;line-height:1;transition:transform .15s ease;color:var(--ink-soft)}.topic-btn-parent.open .topic-caret{transform:rotate(90deg);color:var(--teal-deep)}.topic-caret-spacer{visibility:hidden}.topic-children{display:grid;gap:.15rem;padding-left:.35rem;border-left:2px solid rgba(15,118,110,.12);margin:.05rem 0 .25rem .85rem}.topic-btn-child{padding-left:.7rem;font-size:.9rem;opacity:.92}.browse-toolbar{display:flex;flex-wrap:wrap;gap:.6rem;margin-bottom:1rem}.browse-toolbar input,.browse-toolbar select{border:1px solid var(--line);background:#fffc;border-radius:12px;padding:.65rem .85rem}.browse-toolbar input{flex:1;min-width:180px}.result-count{color:var(--ink-soft);font-size:.9rem;margin-bottom:.75rem}.pager{display:flex;gap:.5rem;align-items:center;margin-top:1.25rem}.pager button:disabled{opacity:.4;cursor:not-allowed}.question-page{padding:1.75rem 0 3rem}.crumb{color:var(--ink-soft);font-size:.88rem;margin-bottom:1rem}.crumb a:hover{color:var(--teal)}.q-hero-title{font-family:var(--font-display);font-size:clamp(1.6rem,3.5vw,2.2rem);line-height:1.25;margin:0 0 .85rem}.feynman-one{font-size:1.15rem;line-height:1.7;max-width:42rem;margin:0 0 1.75rem;padding-left:1rem;border-left:3px solid var(--teal);color:var(--ink)}.feynman-block{margin:2rem 0}.feynman-block h2{font-family:var(--font-display);font-size:1.15rem;margin:0 0 .85rem}.steps{list-style:none;margin:0;padding:0;display:grid;gap:0;position:relative}.step{display:grid;grid-template-columns:2rem 1fr;gap:.85rem;padding:.85rem 0;position:relative}.step:before{content:"";position:absolute;left:.9rem;top:2.2rem;bottom:-.2rem;width:2px;background:#0f766e2e}.step:last-child:before{display:none}.step-index{width:1.8rem;height:1.8rem;border-radius:50%;display:grid;place-items:center;background:var(--teal);color:#fff;font-size:.8rem;font-family:var(--font-display);font-weight:600;position:relative;z-index:1}.step-title{font-weight:600;margin-bottom:.25rem}.step-body{color:var(--ink-soft);line-height:1.65}.analogy-box{background:linear-gradient(135deg,#c45c2614,#0f766e14);border-radius:var(--radius);padding:1.15rem 1.25rem;line-height:1.7;border:1px solid rgba(196,92,38,.15)}.oral-hint{margin:-.35rem 0 .75rem;color:var(--ink-soft);font-size:.92rem}.oral-box{background:#ffffffb8;border:1px solid var(--line);border-radius:var(--radius);padding:1.15rem 1.25rem;line-height:1.75;position:relative}.oral-actions{display:flex;gap:.5rem;margin-bottom:.85rem}.oral-points{list-style:none;margin:0;padding:0;display:grid;gap:.75rem}.oral-point{display:grid;grid-template-columns:1.7rem 1fr;gap:.7rem;align-items:start}.oral-point-index{width:1.7rem;height:1.7rem;border-radius:50%;display:grid;place-items:center;background:#c45c261f;color:var(--accent);font-family:var(--font-display);font-size:.82rem;font-weight:700}.oral-point-body{color:var(--ink);line-height:1.75}.oral-fallback{white-space:pre-wrap}.algo-anim-list{display:grid;gap:1.1rem}.algo-anim{margin:1rem 0 .5rem;padding:1rem 1.1rem 1.1rem;border-radius:var(--radius);border:1px solid var(--line);background:linear-gradient(180deg,#0f766e0f,#ffffffb3)}.algo-anim-head{display:flex;flex-wrap:wrap;gap:.6rem 1rem;align-items:center;justify-content:space-between;margin-bottom:.55rem}.algo-anim-head h3{margin:0;font-family:var(--font-display);font-size:1.05rem}.algo-anim-controls{display:flex;flex-wrap:wrap;gap:.35rem}.algo-anim-label{margin:0 0 .85rem;color:var(--ink-soft);font-size:.92rem;min-height:1.4em}.algo-bars{display:flex;align-items:flex-end;gap:.35rem;min-height:160px;padding:.5rem .25rem 0}.algo-bar{flex:1;min-width:1.4rem;border-radius:8px 8px 4px 4px;background:#0f766e59;display:flex;align-items:flex-start;justify-content:center;color:#fff;font-size:.75rem;font-weight:700;padding-top:.25rem;transition:height .25s ease,background .2s ease,transform .2s ease}.algo-bar.hi{background:var(--accent);transform:translateY(-4px)}.algo-bar.mid{background:#0ea5e9}.algo-bar.pivot{background:#7c3aed}.algo-bar.done{background:var(--ok)}.algo-list{display:flex;flex-wrap:wrap;align-items:center;gap:.35rem;min-height:64px}.algo-node{min-width:2.4rem;padding:.55rem .7rem;border-radius:10px;background:#0f766e1f;border:1px solid rgba(15,118,110,.25);text-align:center;font-weight:700;transition:transform .2s ease,background .2s ease}.algo-node.hi{border-color:var(--accent);background:#c45c261f}.algo-node.new{background:#15803d26;border-color:var(--ok);transform:scale(1.06)}.algo-arrow{color:var(--teal);font-weight:700}.algo-null{color:var(--ink-soft);font-size:.85rem}.algo-stack{display:flex;flex-direction:column;align-items:center;gap:.3rem;min-height:140px;justify-content:flex-end}.algo-stack-item{width:min(160px,70%);padding:.45rem;text-align:center;border-radius:8px;background:#0f766e2e;border:1px solid rgba(15,118,110,.28);font-weight:700}.algo-stack-item.hi{background:#c45c262e;border-color:var(--accent)}.algo-stack-base{font-size:.78rem;color:var(--ink-soft)}.algo-queue{display:flex;flex-wrap:wrap;align-items:center;gap:.4rem;min-height:72px}.algo-q-item{min-width:2.2rem;padding:.5rem .65rem;border-radius:10px;background:#0f766e24;font-weight:700;text-align:center}.algo-q-item.hi{background:#c45c2629}.algo-q-tag{font-size:.78rem;color:var(--ink-soft)}.algo-graph{position:relative;height:220px;border-radius:12px;background:#ffffff8c;overflow:hidden}.algo-g-edges{position:absolute;top:0;right:0;bottom:0;left:0;width:100%;height:100%}.algo-g-edge{stroke:#102a2c40;stroke-width:.6}.algo-g-edge.active{stroke:var(--accent);stroke-width:1.1}.algo-g-node{position:absolute;width:2rem;height:2rem;margin:-1rem 0 0 -1rem;border-radius:50%;display:grid;place-items:center;background:#fff;border:2px solid var(--teal);font-weight:700;font-size:.85rem;z-index:1;transition:background .2s ease,border-color .2s ease,transform .2s ease}.algo-g-node.visited{background:#0f766e26}.algo-g-node.hi{background:var(--accent);border-color:var(--accent);color:#fff;transform:scale(1.08)}.algo-slots{display:flex;flex-wrap:wrap;gap:.4rem;justify-content:center}.algo-slot{min-width:2.6rem;padding:.35rem .4rem;border-radius:10px;border:1px solid var(--line);background:#ffffffb3;text-align:center;transition:background .2s ease,border-color .2s ease}.algo-slot-idx{display:block;font-size:.68rem;color:var(--ink-soft)}.algo-slot-val{font-weight:700;font-size:.92rem}.algo-slot.empty .algo-slot-val{color:var(--ink-soft);font-weight:500}.algo-slot.hi{border-color:var(--accent);background:#d9770629}.algo-slot.done{border-color:var(--teal);background:#0f766e1f}.algo-match{display:grid;gap:.65rem;padding:.85rem 1rem;border-radius:12px;background:#ffffff8c}.algo-match-row{display:flex;flex-wrap:wrap;align-items:center;gap:.25rem}.algo-match-tag{width:1.4rem;font-weight:700;color:var(--ink-soft)}.algo-match-ch{min-width:1.35rem;height:1.7rem;display:grid;place-items:center;border-radius:6px;border:1px solid var(--line);background:#fff;font-family:ui-monospace,Consolas,monospace;font-size:.9rem}.algo-match-ch.hi{border-color:var(--accent);background:#d977062e;font-weight:700}.algo-match-ch.done{border-color:var(--teal);background:#0f766e29}.algo-anim-progress{margin-top:.75rem;font-size:.82rem;color:var(--ink-soft)}.followups{display:grid;gap:.75rem}.followup{padding:.85rem 1rem;border-radius:12px;background:#ffffff8c;border:1px solid var(--line)}.followup-q{font-weight:600;margin-bottom:.3rem}.followup-a{color:var(--ink-soft);line-height:1.6}.related-grid{display:grid;gap:.55rem}.empty,.error,.loading{padding:2rem 0;color:var(--ink-soft)}@media(max-width:820px){.browse-layout{grid-template-columns:1fr}.side-panel{position:static;max-height:min(42vh,320px)}.nav-actions .btn-ghost:nth-child(2){display:none}.hero{padding-top:2.2rem}}