:root {
  --ink: #0b0b0e;
  --ink-2: #131318;
  --ink-3: #1c1c24;
  --paper: #f4f1ea;
  --paper-dim: #a8a49a;
  --paper-faint: #6b6860;
  --accent: #f5a524;
  --accent-2: #4fc3f7;
  --accent-soft: rgba(245, 165, 36, .14);
  --rule: rgba(244, 241, 234, .12);
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
[hidden] { display: none !important; }

body {
  background: var(--ink);
  color: var(--paper);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

.wrap { max-width: 1100px; margin-inline: auto; padding-inline: clamp(20px, 5vw, 48px); }
.num { font-family: var(--mono); font-variant-numeric: tabular-nums; }
.acc { color: var(--accent); }
.fine { font-size: .78rem; color: var(--paper-faint); }
a { color: inherit; }
::selection { background: var(--accent); color: var(--ink); }

.site-header {
  position: fixed; inset-inline: 0; top: 0; z-index: 20;
  background: color-mix(in srgb, var(--ink) 82%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule);
}
.header-row { display: flex; align-items: center; justify-content: space-between; height: 52px; }
.brand { text-decoration: none; font-weight: 700; letter-spacing: .04em; font-size: 1.05rem; }
.brand-latin { font-family: var(--mono); font-size: .62rem; letter-spacing: .32em; color: var(--paper-dim); margin-left: .6em; vertical-align: .18em; }
.top-nav { display: flex; gap: 1.4rem; }
.top-nav a { text-decoration: none; font-size: .85rem; color: var(--paper-dim); transition: color .15s; }
.top-nav a:hover { color: var(--accent); }

main { padding-top: 52px; }

/* ── stage ──────────────────────────── */
.stage { position: relative; height: max(640px, calc(100vh - 52px)); overflow: hidden; border-bottom: 1px solid var(--rule); }
#gl { position: absolute; inset: 0; width: 100%; height: 100%; display: block; touch-action: none; }

.stage-head { position: absolute; top: clamp(20px, 4vh, 44px); left: 0; right: 0; pointer-events: none; z-index: 3; }
.eyebrow { font-family: var(--mono); font-size: .68rem; letter-spacing: .28em; color: var(--accent); margin-bottom: .8rem; }
.stage-head h1 { font-size: clamp(1.9rem, 4.5vw, 3rem); font-weight: 800; line-height: 1.1; }
.h1-latin { display: block; font-family: var(--mono); font-size: .32em; font-weight: 400; letter-spacing: .5em; color: var(--paper-dim); margin-top: .5em; }
.stage-hint { margin-top: .8rem; font-size: .82rem; color: var(--paper-faint); }

.mode-tabs { position: absolute; top: clamp(20px, 4vh, 44px); right: clamp(16px, 3vw, 40px); z-index: 4; display: flex; flex-direction: column; gap: .5rem; }
.mode-tab {
  appearance: none; cursor: pointer; text-align: left;
  background: color-mix(in srgb, var(--ink-2) 88%, transparent);
  border: 1px solid var(--rule); border-radius: 8px;
  color: var(--paper-dim); font: inherit; font-size: .88rem; font-weight: 600;
  padding: .55rem 1rem;
  transition: all .18s;
  backdrop-filter: blur(6px);
}
.mode-tab span { display: block; font-family: var(--mono); font-size: .58rem; letter-spacing: .22em; opacity: .7; }
.mode-tab:hover { color: var(--paper); border-color: var(--paper-dim); }
.mode-tab.is-active { background: var(--accent); border-color: var(--accent); color: var(--ink); }
.mode-tab.is-active span { opacity: .75; }

/* hotspots */
.hotspots { position: absolute; inset: 0; pointer-events: none; z-index: 3; }
.hotspot {
  position: absolute; transform: translate(-50%, -50%);
  display: flex; align-items: center; gap: .45em;
  pointer-events: auto; cursor: pointer;
  font: 600 .78rem/1 var(--sans); color: var(--paper);
  background: color-mix(in srgb, var(--ink-2) 85%, transparent);
  border: 1px solid var(--rule); border-radius: 99px;
  padding: .4em .8em .4em .55em;
  white-space: nowrap;
  transition: opacity .2s, border-color .2s;
  backdrop-filter: blur(4px);
}
.hotspot::before {
  content: ""; width: 8px; height: 8px; border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 8px rgba(245, 165, 36, .8);
  animation: hs-pulse 2.2s ease-in-out infinite;
}
.hotspot.is-rdma::before { background: var(--accent-2); box-shadow: 0 0 8px rgba(79, 195, 247, .8); }
.hotspot:hover, .hotspot.is-open { border-color: var(--accent); }
.hotspot.is-hidden { opacity: 0; pointer-events: none; }
@keyframes hs-pulse { 50% { transform: scale(1.35); } }

/* info panel */
.panel {
  position: absolute; z-index: 5;
  right: clamp(12px, 2.5vw, 32px); bottom: clamp(96px, 14vh, 140px);
  width: min(360px, calc(100vw - 24px));
  max-height: 55vh; overflow-y: auto;
  background: color-mix(in srgb, var(--ink-2) 94%, transparent);
  border: 1px solid var(--rule); border-radius: 12px;
  padding: 1.3rem 1.4rem;
  backdrop-filter: blur(10px);
  box-shadow: 0 20px 60px rgba(0, 0, 0, .5);
}
.panel-close {
  position: absolute; top: .6rem; right: .8rem;
  appearance: none; cursor: pointer;
  background: none; border: none;
  color: var(--paper-faint); font-size: 1.4rem; line-height: 1;
}
.panel-close:hover { color: var(--paper); }
.panel-eyebrow { font-family: var(--mono); font-size: .62rem; letter-spacing: .26em; color: var(--accent); margin-bottom: .4rem; }
.panel-title { font-size: 1.15rem; font-weight: 700; margin-bottom: .6rem; padding-right: 1.4rem; }
.panel-body { font-size: .88rem; color: var(--paper-dim); }
.panel-body p + p { margin-top: .7rem; }
.panel-body strong { color: var(--paper); }
.panel-body .deep-toggle {
  appearance: none; cursor: pointer;
  background: none; border: none;
  color: var(--accent); font: 600 .82rem var(--sans);
  padding: 0; margin-top: .7rem;
}
.panel-body .deep { border-left: 2px solid var(--rule); padding-left: .9rem; margin-top: .7rem; }
.panel-body .spec { font-family: var(--mono); font-size: .72rem; color: var(--paper-faint); margin-top: .8rem; letter-spacing: .04em; }

/* stage bottom UI */
.stage-ui {
  position: absolute; left: 0; right: 0; bottom: 0; z-index: 4;
  display: flex; flex-direction: column; gap: .6rem;
  padding: clamp(12px, 2.5vh, 22px) clamp(16px, 3vw, 40px);
  background: linear-gradient(transparent, rgba(11, 11, 14, .88) 55%);
}
.ui-row { display: flex; align-items: center; justify-content: space-between; gap: 1rem; flex-wrap: wrap; }

.explode-ctl { display: flex; align-items: center; gap: .8rem; font-size: .82rem; color: var(--paper-dim); }
.explode-ctl input[type="range"] { width: min(220px, 40vw); accent-color: var(--accent); }

.ui-btn {
  appearance: none; cursor: pointer;
  background: color-mix(in srgb, var(--ink-2) 85%, transparent);
  border: 1px solid var(--rule); border-radius: 8px;
  color: var(--paper); font: 600 .82rem var(--sans);
  padding: .5rem 1rem;
  transition: all .18s;
  backdrop-filter: blur(4px);
}
.ui-btn:hover { border-color: var(--accent); color: var(--accent); }

.steps { display: flex; gap: .4rem; flex-wrap: wrap; }
.step-dot {
  appearance: none; cursor: pointer;
  width: 30px; height: 30px; border-radius: 50%;
  border: 1px solid var(--rule);
  background: color-mix(in srgb, var(--ink-2) 85%, transparent);
  color: var(--paper-dim); font: 600 .78rem var(--mono);
  display: grid; place-items: center;
  transition: all .18s;
}
.step-dot:hover { border-color: var(--paper-dim); color: var(--paper); }
.step-dot.is-current { background: var(--accent-2); border-color: var(--accent-2); color: var(--ink); }
.step-dot.is-done { color: var(--accent-2); border-color: color-mix(in srgb, var(--accent-2) 50%, transparent); }

.step-nav { display: flex; align-items: center; gap: .6rem; }
.step-count { font-size: .85rem; color: var(--paper-dim); }

#rdma-ui { justify-content: space-between; }

.loading, .gl-fail {
  position: absolute; inset: 0; z-index: 6;
  display: grid; place-items: center;
  background: var(--ink);
  font-family: var(--mono); font-size: .85rem; letter-spacing: .2em;
  color: var(--paper-dim);
  text-align: center; line-height: 2;
}
.loading.is-done { display: none; }

/* ── deep section ───────────────────── */
.section { padding-block: clamp(72px, 12vh, 130px); border-bottom: 1px solid var(--rule); }
.sec-head { margin-bottom: clamp(2.5rem, 6vh, 4.5rem); }
.sec-no { font-family: var(--mono); font-size: .8rem; letter-spacing: .3em; color: var(--accent); margin-bottom: .5rem; }
h2 { font-size: clamp(1.9rem, 4.5vw, 3rem); font-weight: 800; }
h2 .latin { font-family: var(--mono); font-size: .38em; font-weight: 400; letter-spacing: .3em; color: var(--paper-dim); margin-left: 1em; }
.sec-lead { margin-top: .8rem; color: var(--paper-dim); max-width: 36em; }

.why-wrap { max-width: 780px; }
.essay p + p { margin-top: 1.2rem; }
.essay strong { color: var(--paper); }
.essay-tail { padding-top: 1rem; border-top: 1px solid var(--rule); color: var(--paper-dim); }
.essay-tail a { color: var(--accent); }

.site-footer { padding-block: 64px 80px; }
.foot-title { font-weight: 700; margin-bottom: 1rem; }
.family { list-style: none; display: flex; flex-wrap: wrap; gap: .4rem 1.6rem; }
.family a { text-decoration: none; color: var(--paper-dim); font-size: .9rem; transition: color .15s; }
.family a:hover { color: var(--accent); }
.site-footer .fine { margin-top: 2.2rem; }

@media (max-width: 760px) {
  .top-nav { display: none; }
  .mode-tabs { top: auto; bottom: 150px; flex-direction: row; }
  .mode-tab { padding: .45rem .8rem; font-size: .8rem; }
  .panel { right: 12px; left: 12px; width: auto; bottom: 118px; max-height: 42vh; }
  .stage-head h1 { font-size: 1.7rem; }
  .stage-hint { display: none; }
  #anatomy-ui { flex-direction: column; align-items: stretch; }
  .step-nav { justify-content: center; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .hotspot::before { animation: none; }
  * { transition-duration: .01ms !important; }
}