/* SYSTEM UNDER PRESSURE — dark theme.
   Palette follows pedoman visual v3 §6: dark surfaces only, accents for
   type, strokes and highlights. Soft pastel accents for eye comfort. */
:root {
  --void: #090D12;
  --panel: #0F1720;
  --panel2: #141E28;
  --border: #1C2936;
  --border2: #2B3D4F;
  --ink: #E4ECF0;
  --ink2: #A9B8C4;   /* body text: 9.6:1 on void */
  --dim: #8A9BB0;    /* secondary: 6.6:1 on void */
  --ink3: #5A6E7C;   /* decorative only, never for readable text */
  --mint: #88D4C0;
  --amber: #E6C594;
  --slate: #8DA9C4;
  --lav: #B8A1D9;
  --rose: #E58B8B;
  --mono: 'JetBrains Mono', ui-monospace, 'Cascadia Mono', Consolas, monospace;
  --sans: 'IBM Plex Sans', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --measure: 70ch;
  --radius: 14px;
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: 88px; }
@media (prefers-reduced-motion: no-preference) { html { scroll-behavior: smooth; } }

body {
  margin: 0;
  background: var(--void);
  background-image:
    linear-gradient(rgba(121,147,168,.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(121,147,168,.035) 1px, transparent 1px);
  background-size: 72px 72px;
  background-attachment: fixed;
  color: var(--ink2);
  font: 400 1.0625rem/1.75 var(--sans);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--mint); text-underline-offset: .18em; text-decoration-thickness: 1px; }
a:hover { color: var(--ink); }
:focus-visible { outline: 2px solid var(--amber); outline-offset: 3px; border-radius: 4px; }

.sr-only {
  position: absolute !important; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.skip {
  position: absolute; left: 12px; top: -60px; z-index: 100;
  background: var(--amber); color: var(--void); padding: 10px 16px;
  border-radius: 8px; font-weight: 600; text-decoration: none;
}
.skip:focus { top: 12px; }

/* ── Reading progress ─────────────────────────────── */
.progress-bar { position: fixed; top: 0; left: 0; right: 0; height: 3px; z-index: 60; }
.progress-bar span { display: block; height: 100%; width: 0; background: var(--amber); }
body:not([data-session]) .progress-bar { display: none; }

/* ── Top bar ──────────────────────────────────────── */
.topbar {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
  padding: 14px clamp(16px, 4vw, 40px);
  background: rgba(9,13,18,.86);
  backdrop-filter: blur(10px); -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.brand {
  font: 800 .95rem/1 var(--mono); letter-spacing: .04em;
  color: var(--ink); text-decoration: none; white-space: nowrap;
}
.brand-mark { color: var(--dim); }
.topnav { display: flex; align-items: center; gap: 8px; }
.navlink {
  color: var(--dim); text-decoration: none; font-size: .9rem;
  padding: 8px 10px; border-radius: 8px;
}
.navlink:hover { color: var(--ink); background: var(--panel); }

.lang-switch {
  display: inline-flex; align-items: center; gap: 6px;
  min-height: 44px; padding: 0 16px;
  border: 1px solid var(--border2); border-radius: 999px;
  background: var(--panel);
  font: 700 .82rem/1 var(--mono); letter-spacing: .06em;
  text-decoration: none; color: var(--dim);
  transition: border-color .2s, background .2s;
}
.lang-switch:hover { border-color: var(--mint); background: var(--panel2); color: var(--dim); }
.lang-cur { color: var(--mint); }
.lang-sep { color: var(--ink3); }
.lang-oth { color: var(--dim); }
.lang-switch:hover .lang-oth { color: var(--ink); }

@media (max-width: 560px) {
  .navlink { display: none; }
  .brand { font-size: .82rem; }
  .index { padding-top: 24px; }
  .hero { padding-top: 8px; }
}

/* ── Buttons ──────────────────────────────────────── */
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  min-height: 46px; padding: 0 22px; border-radius: 999px;
  border: 1px solid var(--border2); background: var(--panel);
  color: var(--ink); font: 600 .95rem/1 var(--sans); text-decoration: none;
  cursor: pointer; transition: border-color .2s, background .2s, transform .2s;
}
.btn:hover { border-color: var(--mint); color: var(--ink); }
.btn-primary { border-color: var(--mint); color: var(--mint); background: rgba(136,212,192,.08); }
.btn-primary:hover { background: rgba(136,212,192,.14); color: var(--ink); }

/* ── Index ────────────────────────────────────────── */
main { flex: 1; }
.index { width: min(1080px, 100% - 32px); margin: 0 auto; padding: 56px 0 40px; }

.eyebrow {
  margin: 0 0 12px; font: 700 .78rem/1.4 var(--mono);
  letter-spacing: .14em; text-transform: uppercase; color: var(--dim);
}
.eyebrow a { color: inherit; text-decoration: none; }
.eyebrow a:hover { color: var(--mint); }

.hero { padding: 24px 0 40px; border-bottom: 1px solid var(--border); }
.hero h1 {
  margin: 0; color: var(--ink);
  font: 800 clamp(2.4rem, 7vw, 4.6rem)/1.02 var(--mono); letter-spacing: -.03em;
}
.hero .accent { color: var(--amber); }
.tagline { margin: 18px 0 8px; color: var(--ink); font-size: clamp(1.05rem, 2.2vw, 1.3rem); font-weight: 500; }
.intro { margin: 0; max-width: 62ch; color: var(--ink2); }
.hero-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 20px 32px; margin-top: 30px; }
.overall { min-width: 220px; }
.overall p { margin: 8px 0 0; font: 500 .85rem/1.4 var(--mono); color: var(--dim); }
.overall strong { color: var(--amber); font-weight: 800; }
.overall-track { height: 6px; border-radius: 99px; background: var(--panel2); overflow: hidden; }
.overall-track span { display: block; height: 100%; width: 0; background: var(--amber); transition: width .5s ease; }
.done-all { margin: 18px 0 0; color: var(--mint); font-weight: 500; }

.filter { margin: 36px 0 8px; }
.filter input {
  width: 100%; max-width: 420px; min-height: 46px; padding: 0 16px;
  background: var(--panel); color: var(--ink);
  border: 1px solid var(--border2); border-radius: 10px;
  font: 400 1rem var(--sans);
}
.filter input::placeholder { color: var(--dim); }
.filter input:focus { outline: none; border-color: var(--mint); box-shadow: 0 0 0 3px rgba(136,212,192,.15); }
.no-match { color: var(--dim); margin: 16px 0 0; }

.level { padding: 40px 0 8px; }
.level[hidden] { display: none; }
.level-head { margin-bottom: 18px; }
.level-tag { margin: 0 0 6px; font: 700 .76rem/1.4 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--amber); }
.level-head h2 { margin: 0; color: var(--ink); font: 800 clamp(1.4rem, 3.4vw, 1.9rem)/1.2 var(--mono); letter-spacing: -.02em; }
.level-q { margin: 6px 0 0; color: var(--dim); max-width: 62ch; }

.cards {
  list-style: none; margin: 0; padding: 0;
  display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 12px;
}
.card[hidden] { display: none; }
.card a {
  display: flex; align-items: center; gap: 16px; height: 100%;
  padding: 16px 18px; border-radius: var(--radius);
  background: var(--panel); border: 1px solid var(--border);
  text-decoration: none; color: inherit;
  transition: border-color .2s, background .2s, transform .2s;
}
.card a:hover { border-color: var(--border2); background: var(--panel2); }
@media (prefers-reduced-motion: no-preference) { .card a:hover { transform: translateY(-2px); } }
.card-num { flex: none; font: 800 1.5rem/1 var(--mono); color: var(--dim); min-width: 2.2ch; }
.card-body { flex: 1; display: flex; flex-direction: column; gap: 4px; min-width: 0; }
.card-title { color: var(--ink); font-weight: 500; line-height: 1.4; }
.card-meta { font: 500 .76rem/1 var(--mono); color: var(--dim); letter-spacing: .04em; }
.card-check {
  flex: none; width: 22px; height: 22px; border-radius: 50%;
  border: 1.5px solid var(--border2);
}
.card.is-done .card-check { border-color: var(--mint); background: var(--mint) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24'%3E%3Cpath d='M6 12.5l4 4 8-9' fill='none' stroke='%23090D12' stroke-width='2.6' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E") center/14px no-repeat; }
.card.is-done .card-num { color: var(--mint); }

.how { margin: 48px 0 0; padding: 26px 28px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--panel); }
.how h2 { margin: 0 0 10px; color: var(--ink); font: 700 1.1rem/1.3 var(--mono); }
.how ul { margin: 0; padding-left: 1.2em; }
.how li { margin: 6px 0; }

/* ── Session page ─────────────────────────────────── */
.session-layout {
  width: min(1180px, 100% - 32px); margin: 0 auto; padding: 48px 0 40px;
  display: grid; grid-template-columns: minmax(0, 1fr) 240px; gap: 56px;
}
@media (max-width: 1000px) { .session-layout { grid-template-columns: minmax(0, 1fr); } .toc { display: none; } }

.session { min-width: 0; max-width: var(--measure); }
.session-head { padding-bottom: 28px; margin-bottom: 36px; border-bottom: 1px solid var(--border); }
.session-num { margin: 0; font: 800 clamp(3.5rem, 11vw, 6rem)/.9 var(--mono); color: var(--panel2); letter-spacing: -.04em;
  -webkit-text-stroke: 1px var(--border2); }
.session-head h1 { margin: 10px 0 0; color: var(--ink); font: 800 clamp(1.7rem, 4.6vw, 2.6rem)/1.15 var(--mono); letter-spacing: -.02em; }
.hook { margin: 20px 0 0; padding-left: 18px; border-left: 3px solid var(--amber); color: var(--ink); font-size: 1.12rem; line-height: 1.65; }
.hook em { font-style: italic; }
.meta { display: flex; flex-wrap: wrap; gap: 8px 20px; margin: 22px 0 0; font: 500 .8rem/1.4 var(--mono); color: var(--dim); letter-spacing: .04em; }
.notice { margin: 20px 0 0; padding: 12px 16px; border: 1px solid var(--border2); border-radius: 10px; background: var(--panel); color: var(--amber); font-size: .92rem; }

/* prose */
.prose { color: var(--ink2); }
.prose > :first-child { margin-top: 0; }
.prose h2 {
  margin: 56px 0 16px; color: var(--ink);
  font: 800 clamp(1.3rem, 3vw, 1.6rem)/1.25 var(--mono); letter-spacing: -.01em;
}
.prose h3 { margin: 36px 0 10px; color: var(--ink); font: 700 1.12rem/1.35 var(--sans); }
.prose p, .prose ul, .prose ol { margin: 0 0 1.15em; }
.prose li { margin: .35em 0; }
.prose li::marker { color: var(--dim); }
.prose strong { color: var(--ink); font-weight: 600; }
.prose em { color: var(--ink); }
.prose hr { border: 0; border-top: 1px solid var(--border); margin: 40px 0; }
.prose blockquote {
  margin: 1.4em 0; padding: 14px 20px;
  background: var(--panel); border-left: 3px solid var(--slate); border-radius: 0 10px 10px 0;
  color: var(--ink);
}
.prose blockquote p:last-child { margin-bottom: 0; }
.prose code {
  font: 500 .88em/1 var(--mono); color: var(--amber);
  background: var(--panel2); padding: .15em .4em; border-radius: 5px;
}
.prose pre {
  margin: 1.4em 0; padding: 18px 20px; overflow-x: auto;
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px;
}
.prose pre code { background: none; padding: 0; color: var(--ink2); font-size: .86rem; line-height: 1.6; }

.table-wrap { margin: 1.5em 0; overflow-x: auto; border: 1px solid var(--border); border-radius: 12px; }
.prose table { width: 100%; border-collapse: collapse; font-size: .94rem; }
.prose th, .prose td { padding: 11px 14px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); }
.prose th { background: var(--panel2); color: var(--ink); font: 700 .78rem/1.4 var(--mono); letter-spacing: .05em; text-transform: uppercase; }
.prose tr:last-child td { border-bottom: 0; }
.prose tbody tr:nth-child(even) td { background: rgba(15,23,32,.6); }

.math-display { margin: 1.4em 0; padding: 16px 18px; overflow-x: auto;
  background: var(--panel); border: 1px solid var(--border); border-radius: 12px; color: var(--ink); }
.math-inline { color: var(--ink); }
.prose .katex { font-size: 1.08em; }

/* end of session */
.session-end { margin: 56px 0 0; padding-top: 28px; border-top: 1px solid var(--border); }
.mark-done {
  min-height: 46px; padding: 0 22px; border-radius: 999px; cursor: pointer;
  border: 1px solid var(--border2); background: var(--panel); color: var(--ink);
  font: 600 .95rem/1 var(--sans); transition: border-color .2s, background .2s, color .2s;
}
.mark-done:hover { border-color: var(--mint); }
.mark-done[aria-pressed="true"] { border-color: var(--mint); color: var(--mint); background: rgba(136,212,192,.08); }

.prevnext { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 28px; }
.pn {
  display: flex; flex-direction: column; gap: 6px; padding: 16px 18px;
  border: 1px solid var(--border); border-radius: var(--radius); background: var(--panel);
  text-decoration: none; transition: border-color .2s, background .2s;
}
.pn:hover { border-color: var(--border2); background: var(--panel2); }
.pn-next { text-align: right; }
.pn-label { font: 700 .74rem/1.3 var(--mono); letter-spacing: .08em; text-transform: uppercase; color: var(--dim); }
.pn-title { color: var(--ink); font-weight: 500; line-height: 1.4; }
@media (max-width: 560px) { .prevnext { grid-template-columns: 1fr; } .pn-next { text-align: left; } .pn-empty { display: none; } }

/* toc */
.toc { position: sticky; top: 96px; align-self: start; max-height: calc(100vh - 120px); overflow-y: auto; }
.toc-title { margin: 0 0 10px; font: 700 .74rem/1.4 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--dim); }
.toc ol { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--border); }
.toc a {
  display: block; padding: 7px 0 7px 14px; margin-left: -1px;
  border-left: 2px solid transparent; color: var(--dim);
  text-decoration: none; font-size: .88rem; line-height: 1.4;
}
.toc a:hover { color: var(--ink); }
.toc a.is-active { color: var(--mint); border-left-color: var(--mint); }

/* ── Footer / 404 ─────────────────────────────────── */
.footer {
  width: min(1180px, 100% - 32px); margin: 40px auto 0; padding: 28px 0 40px;
  border-top: 1px solid var(--border); color: var(--dim); font-size: .9rem;
}
.footer p { margin: 0 0 4px; }
.footer-meta { font: 500 .78rem/1.4 var(--mono); letter-spacing: .04em; }

.notfound { width: min(640px, 100% - 32px); margin: 0 auto; padding: 18vh 0; }
.notfound h1 { color: var(--ink); font: 800 2.4rem/1.1 var(--mono); margin: 10px 0 14px; }
.notfound .btn { margin: 20px 10px 0 0; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
}
@media print {
  .topbar, .toc, .prevnext, .session-end, .progress-bar, .footer { display: none !important; }
  body { background: #fff; color: #111; }
  .prose, .prose strong, .session-head h1 { color: #111; }
}