/* ============================================================
   Paper explainers — shared design system
   Light theme, mobile-first, self-contained.
   Used by /papers/index.html and every /papers/<slug>.html
   ============================================================ */

:root{
  --ink:#1a1a1a; --muted:#5b6470; --line:#e3e6ea; --bg:#ffffff;
  --card:#f7f9fb; --card2:#eef2f7;
  --accent:#4f46e5;         /* indigo — site primary */
  --accent-soft:#eef0fe;
  --teal:#0d9488; --teal-soft:#eafaf6;
  --amber:#b45309; --amber-soft:#fdf6ec;
  --purple:#6d28d9; --purple-soft:#f4effd;
  --red:#b91c1c; --red-soft:#fdecec;
  --green:#15803d; --green-soft:#ecfaf0;
  --maxw:940px;
}
*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--ink);
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  line-height:1.62;font-size:17px;-webkit-text-size-adjust:100%}
.wrap{max-width:var(--maxw);margin:0 auto;padding:26px 20px 90px}

a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}

/* ---- top nav crumb ---- */
.crumb{font-size:.85rem;color:var(--muted);margin-bottom:18px}
.crumb a{color:var(--muted)}
.crumb a:hover{color:var(--accent)}

/* ---- headings ---- */
h1{font-size:2.05rem;line-height:1.14;margin:.1em 0 .2em;letter-spacing:-.01em}
h2{font-size:1.5rem;margin:2.1em 0 .4em;border-top:2px solid var(--line);padding-top:.7em}
h3{font-size:1.17rem;margin:1.4em 0 .3em}
h4{font-size:1.02rem;margin:1.1em 0 .2em}
.part{font-size:.78rem;letter-spacing:.13em;text-transform:uppercase;color:var(--accent);
  font-weight:700;margin:2.4em 0 -.3em}
p{margin:.62em 0}
.lead{font-size:1.08rem;color:#2c333c}
ul,ol{margin:.5em 0 .5em;padding-left:1.4em}
li{margin:.28em 0}
strong,b{color:#111}

/* ---- paper header block ---- */
header.hero{border-bottom:1px solid var(--line);padding-bottom:20px}
.hero .sub{color:var(--muted);font-size:1.05rem;margin:.35em 0 0}
.meta{display:flex;flex-wrap:wrap;gap:6px 8px;margin:14px 0 0;align-items:center}
.pill{display:inline-block;background:var(--card2);color:#3b4553;border-radius:999px;
  padding:3px 11px;font-size:.78rem;font-weight:500}
.pill.theme{background:var(--accent-soft);color:#3730a3}
.pill.venue{background:#f1f5f9;color:#475569}
.pill.date{background:#f1f5f9;color:#475569}
.pill a{color:inherit}
.authors{color:var(--muted);font-size:.9rem;margin-top:8px}

/* ---- verdict badge ---- */
.verdict{display:inline-flex;align-items:center;gap:8px;border-radius:10px;
  padding:6px 13px;font-weight:700;font-size:.9rem;margin-top:12px}
.verdict.hot{background:var(--red-soft);color:var(--red)}
.verdict.strong{background:var(--green-soft);color:var(--green)}
.verdict.interesting{background:var(--purple-soft);color:var(--purple)}
.verdict.mixed{background:var(--amber-soft);color:var(--amber)}

/* ---- table of contents ---- */
.toc{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px 18px;margin:22px 0}
.toc h4{margin:.1em 0 .5em;font-size:.76rem;letter-spacing:.09em;text-transform:uppercase;color:var(--muted)}
.toc ol{margin:.3em 0;padding-left:1.3em}
.toc li{margin:.16em 0}

/* ---- callouts ---- */
.callout{border-left:4px solid var(--accent);background:var(--accent-soft);
  border-radius:0 10px 10px 0;padding:13px 17px;margin:18px 0}
.callout h4{margin:0 0 .3em;font-size:1rem}
.callout p:last-child{margin-bottom:0}
.callout.key{border-left-color:var(--teal);background:var(--teal-soft)}
.callout.warn{border-left-color:var(--amber);background:var(--amber-soft)}
.callout.take{border-left-color:var(--purple);background:var(--purple-soft)}
.callout.tldr{border-left-color:var(--accent);background:var(--accent-soft)}

/* the "my take" box gets extra emphasis */
.take-box{border:1px solid #e3d9fb;background:linear-gradient(180deg,#faf7ff,#f4effd);
  border-radius:14px;padding:18px 20px;margin:24px 0}
.take-box .tag{display:inline-block;font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;
  font-weight:700;color:var(--purple);background:#fff;border:1px solid #e3d9fb;
  border-radius:999px;padding:3px 11px;margin-bottom:8px}
.take-box h3{margin:.1em 0 .3em}

/* ---- figures / SVG ---- */
figure{margin:20px 0;background:var(--card);border:1px solid var(--line);border-radius:12px;
  padding:16px;text-align:center}
figure svg,figure img{max-width:100%;height:auto}
figcaption{color:var(--muted);font-size:.87rem;margin-top:10px;text-align:left}
figcaption b{color:#333}

/* ---- tables ---- */
.table-wrap{overflow-x:auto;margin:16px 0}
table{border-collapse:collapse;width:100%;font-size:.93rem}
th,td{border:1px solid var(--line);padding:9px 12px;text-align:left;vertical-align:top}
th{background:var(--card);font-weight:600}
tr:nth-child(even) td{background:#fcfdfe}
td.num,th.num{text-align:right;font-variant-numeric:tabular-nums}
.hl{background:#fff4e0}

/* ---- code / equations ---- */
code{background:#eef1f4;padding:1px 6px;border-radius:5px;font-size:.9em;
  font-family:"SF Mono",ui-monospace,Menlo,Consolas,monospace}
pre{background:#0f172a;color:#e2e8f0;border-radius:10px;padding:14px 16px;overflow-x:auto;
  font-family:"SF Mono",ui-monospace,Menlo,Consolas,monospace;font-size:.86rem;line-height:1.55}
pre code{background:none;padding:0;color:inherit;font-size:1em}
.katex-display{overflow-x:auto;overflow-y:hidden;padding:4px 0}

/* small helper labels */
.kv{display:grid;grid-template-columns:170px 1fr;gap:6px 14px;margin:14px 0;font-size:.94rem}
.kv dt{color:var(--muted);font-weight:600}
.kv dd{margin:0}

footer{margin-top:52px;border-top:1px solid var(--line);padding-top:18px;color:var(--muted);font-size:.85rem}
footer a{color:var(--muted)}

/* ============================================================
   Feedback widget (paper pages)
   ============================================================ */
.feedback{border:1px solid var(--line);border-radius:16px;background:var(--card);
  padding:20px 22px;margin:40px 0 0;box-shadow:0 1px 3px rgba(0,0,0,.04)}
.feedback h3{margin:.1em 0 .2em;font-size:1.2rem}
.feedback .fb-sub{color:var(--muted);font-size:.92rem;margin:0 0 14px}
.fb-row{margin:14px 0}
.fb-q{font-weight:600;font-size:.95rem;margin-bottom:7px}
.fb-btns{display:flex;flex-wrap:wrap;gap:8px}
.fb-btn{font:inherit;font-size:.9rem;background:#fff;color:#374151;border:1px solid var(--line);
  border-radius:9px;padding:8px 14px;cursor:pointer;transition:all .12s}
.fb-btn:hover{border-color:var(--accent);color:var(--accent)}
.fb-btn.sel{background:var(--accent);border-color:var(--accent);color:#fff}
.fb-btn.good.sel{background:var(--green);border-color:var(--green)}
.fb-btn.bad.sel{background:var(--red);border-color:var(--red)}
.fb-stars{display:flex;gap:4px}
.fb-star{font-size:1.55rem;line-height:1;cursor:pointer;color:#d1d5db;transition:color .1s;
  background:none;border:none;padding:0 2px}
.fb-star.on{color:#f59e0b}
.feedback textarea{width:100%;min-height:78px;border:1px solid var(--line);border-radius:10px;
  padding:10px 12px;font:inherit;font-size:.94rem;resize:vertical;background:#fff}
.feedback textarea:focus{outline:2px solid var(--accent-soft);border-color:var(--accent)}
.fb-submit{font:inherit;font-weight:600;font-size:.95rem;background:var(--accent);color:#fff;
  border:0;border-radius:10px;padding:10px 20px;cursor:pointer;margin-top:6px}
.fb-submit:hover{filter:brightness(1.07)}
.fb-submit:disabled{opacity:.55;cursor:default}
.fb-thanks{color:var(--green);font-weight:600;margin-top:10px;display:none}
.fb-tally{color:var(--muted);font-size:.82rem;margin-top:10px}

/* ============================================================
   Index page
   ============================================================ */
.index-hero{padding:8px 0 6px}
.index-hero h1{font-size:2.3rem}
.index-hero .sub{font-size:1.12rem;color:var(--muted);max-width:70ch}
.filters{display:flex;flex-wrap:wrap;gap:8px;margin:22px 0 10px}
.chip{font:inherit;font-size:.85rem;background:#fff;border:1px solid var(--line);color:#3b4553;
  border-radius:999px;padding:6px 14px;cursor:pointer;transition:all .12s}
.chip:hover{border-color:var(--accent);color:var(--accent)}
.chip.active{background:var(--accent);border-color:var(--accent);color:#fff}
.cards{display:grid;grid-template-columns:1fr;gap:14px;margin:14px 0}
.pcard{display:block;border:1px solid var(--line);border-radius:14px;background:#fff;
  padding:18px 20px;text-decoration:none;color:var(--ink);transition:all .14s;
  box-shadow:0 1px 3px rgba(0,0,0,.04)}
.pcard:hover{border-color:var(--accent);box-shadow:0 6px 16px -6px rgba(79,70,229,.28);
  transform:translateY(-2px);text-decoration:none}
.pcard .num{font-size:.78rem;color:var(--muted);font-weight:700;letter-spacing:.05em}
.pcard h3{margin:.15em 0 .25em;font-size:1.24rem;line-height:1.25}
.pcard .idea{color:#2c333c;font-size:.98rem;margin:.3em 0 .5em}
.pcard .card-meta{display:flex;flex-wrap:wrap;gap:6px;align-items:center;margin-top:10px}
.pcard .verdict{margin-top:0;font-size:.8rem;padding:4px 10px}
.section-lead{font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);
  font-weight:700;margin:30px 0 4px}

/* ---- responsive ---- */
@media (min-width:720px){
  .cards{grid-template-columns:1fr 1fr}
}
@media (max-width:768px){
  body{font-size:16px}
  .wrap{padding:18px 15px 64px}
  h1{font-size:1.62rem}
  .index-hero h1{font-size:1.8rem}
  h2{font-size:1.28rem}
  .kv{grid-template-columns:1fr;gap:2px 0}
  .kv dt{margin-top:8px}
  .feedback{padding:16px 16px}
}