/* ============================================================
   1.602176634 · The Elementary Charge — styles
   ============================================================ */

:root {
  --bg: #05070f;
  --bg-2: #0a0f1f;
  --panel: rgba(16, 24, 48, 0.55);
  --panel-solid: #0e1530;
  --line: rgba(120, 180, 255, 0.14);
  --line-strong: rgba(120, 180, 255, 0.3);
  --text: #e7eefc;
  --text-dim: #93a3c4;
  --text-faint: #5d6b8c;
  --accent: #00d4ff;
  --accent-2: #4f8cff;
  --accent-glow: rgba(0, 212, 255, 0.55);
  --warm: #ff7a45;
  --radius: 16px;
  --shadow: 0 20px 60px -20px rgba(0, 120, 255, 0.25);
  --maxw: 1080px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 90px; }

body {
  font-family: "Inter", "Noto Sans SC", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* language: when body is EN, hide zh text nodes; when ZH, hide en.
   The visible inline text in the source is the zh default. We use
   ::before content swap instead, driven by data attributes in JS.
   Simpler: JS sets textContent. CSS just handles the toggle button. */

/* background canvas */
#bg-canvas {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: -2;
  opacity: 0.9;
}

/* a soft vignette + gradient over the canvas */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(1200px 800px at 70% -10%, rgba(79, 140, 255, 0.18), transparent 60%),
    radial-gradient(900px 700px at 10% 100%, rgba(0, 212, 255, 0.10), transparent 55%),
    linear-gradient(180deg, var(--bg) 0%, var(--bg-2) 100%);
  pointer-events: none;
}

::selection { background: var(--accent-glow); color: #fff; }

a { color: inherit; text-decoration: none; }

code {
  font-family: "JetBrains Mono", monospace;
  background: rgba(0, 212, 255, 0.1);
  color: var(--accent);
  padding: 0.1em 0.45em;
  border-radius: 6px;
  font-size: 0.9em;
  border: 1px solid var(--line);
}

em { font-style: italic; color: var(--accent); }
strong { color: #fff; font-weight: 600; }

/* ===== navigation ===== */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  transition: background 0.4s var(--ease), backdrop-filter 0.4s, border-color 0.4s;
  border-bottom: 1px solid transparent;
}
.nav.scrolled {
  background: rgba(5, 7, 15, 0.7);
  backdrop-filter: blur(18px) saturate(140%);
  -webkit-backdrop-filter: blur(18px) saturate(140%);
  border-bottom-color: var(--line);
}
.nav-inner {
  max-width: 1180px;
  margin: 0 auto;
  padding: 16px 28px;
  display: flex;
  align-items: center;
  gap: 24px;
}
.brand {
  display: flex;
  align-items: baseline;
  gap: 10px;
  font-weight: 700;
}
.brand-e {
  font-family: "JetBrains Mono", monospace;
  font-size: 1.5rem;
  color: var(--accent);
  text-shadow: 0 0 18px var(--accent-glow);
}
.brand-num {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.95rem;
  color: var(--text-dim);
  letter-spacing: 0.5px;
}
.nav-links {
  display: flex;
  gap: 6px;
  margin-left: auto;
  flex-wrap: wrap;
}
.nav-links a {
  font-size: 0.86rem;
  color: var(--text-dim);
  padding: 8px 12px;
  border-radius: 8px;
  transition: color 0.25s, background 0.25s;
  white-space: nowrap;
}
.nav-links a:hover { color: var(--text); background: rgba(255,255,255,0.04); }

.lang-toggle {
  background: rgba(0, 212, 255, 0.08);
  border: 1px solid var(--line-strong);
  color: var(--text);
  font-family: "JetBrains Mono", monospace;
  font-size: 0.8rem;
  padding: 7px 12px;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.25s;
  display: flex;
  align-items: center;
  gap: 4px;
  white-space: nowrap;
}
.lang-toggle:hover { border-color: var(--accent); background: rgba(0,212,255,0.16); }
.lang-toggle .lang-sep { color: var(--text-faint); }
.lang-toggle .lang-zh.active,
.lang-toggle .lang-en.active { color: var(--accent); font-weight: 700; }

/* ===== hero ===== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  position: relative;
  padding: 120px 24px 80px;
  overflow: hidden;
}
.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(120,180,255,0.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(120,180,255,0.06) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 70% 60% at 50% 45%, #000 30%, transparent 80%);
  -webkit-mask-image: radial-gradient(ellipse 70% 60% at 50% 45%, #000 30%, transparent 80%);
  animation: gridDrift 30s linear infinite;
}
@keyframes gridDrift {
  to { background-position: 60px 60px; }
}
.hero-content { position: relative; z-index: 2; }
.hero-eyebrow {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.8rem;
  letter-spacing: 3px;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 28px;
  opacity: 0.9;
}
.hero-number {
  font-family: "JetBrains Mono", monospace;
  font-weight: 700;
  font-size: clamp(2.8rem, 11vw, 8.5rem);
  line-height: 1;
  letter-spacing: -0.02em;
  background: linear-gradient(180deg, #ffffff 0%, #bfe6ff 60%, var(--accent) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  text-shadow: 0 0 80px rgba(0, 212, 255, 0.3);
  animation: heroFade 1.2s var(--ease) both;
}
.hero-unit {
  font-family: "JetBrains Mono", monospace;
  font-size: clamp(1.1rem, 3.2vw, 2rem);
  color: var(--text-dim);
  margin-top: 12px;
  letter-spacing: 1px;
  animation: heroFade 1.2s var(--ease) 0.15s both;
}
.hero-title {
  font-family: "Space Grotesk", sans-serif;
  font-weight: 600;
  font-size: clamp(1.6rem, 5vw, 3rem);
  margin-top: 36px;
  letter-spacing: -0.01em;
  animation: heroFade 1.2s var(--ease) 0.3s both;
}
.hero-subtitle {
  max-width: 560px;
  margin: 18px auto 0;
  color: var(--text-dim);
  font-size: clamp(0.95rem, 2.4vw, 1.15rem);
  animation: heroFade 1.2s var(--ease) 0.45s both;
}
.hero-domain {
  margin-top: 30px;
  font-size: 0.92rem;
  color: var(--text-faint);
  animation: heroFade 1.2s var(--ease) 0.6s both;
}
@keyframes heroFade {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}
.scroll-cue {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  margin-top: 56px;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.75rem;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--text-dim);
  animation: heroFade 1.2s var(--ease) 0.75s both;
}
.scroll-arrow {
  width: 1px; height: 38px;
  background: linear-gradient(var(--accent), transparent);
  position: relative;
  animation: scrollPulse 2s ease-in-out infinite;
}
@keyframes scrollPulse {
  0%,100% { opacity: 0.4; transform: scaleY(0.7); }
  50% { opacity: 1; transform: scaleY(1); }
}

/* ===== sections ===== */
.section {
  padding: 110px 24px;
  position: relative;
}
.section-alt { background: rgba(8, 12, 28, 0.5); }
.container { max-width: var(--maxw); margin: 0 auto; }

.section-head {
  display: flex;
  align-items: baseline;
  gap: 18px;
  margin-bottom: 48px;
}
.section-index {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.85rem;
  color: var(--accent);
  border: 1px solid var(--line-strong);
  padding: 4px 10px;
  border-radius: 8px;
  letter-spacing: 1px;
}
.section-title {
  font-family: "Space Grotesk", sans-serif;
  font-weight: 600;
  font-size: clamp(1.5rem, 4.5vw, 2.4rem);
  letter-spacing: -0.01em;
  line-height: 1.2;
}
.section-intro {
  font-size: 1.1rem;
  color: var(--text-dim);
  max-width: 680px;
  margin-bottom: 56px;
}

.content-col {
  max-width: 760px;
  font-size: 1.02rem;
  color: var(--text-dim);
}
.content-col p { margin-bottom: 20px; }
.subhead {
  font-family: "Space Grotesk", sans-serif;
  font-size: 1.25rem;
  color: var(--text);
  margin: 40px 0 16px;
  font-weight: 500;
}
.footnote {
  margin-top: 32px;
  font-size: 0.88rem;
  color: var(--text-faint);
  border-left: 2px solid var(--line-strong);
  padding-left: 16px;
  max-width: 760px;
}

/* ===== cards ===== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 22px;
  margin-bottom: 40px;
}
.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 30px 26px;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transition: transform 0.4s var(--ease), border-color 0.4s, box-shadow 0.4s;
  position: relative;
  overflow: hidden;
}
.card::after {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  opacity: 0;
  transition: opacity 0.4s;
}
.card:hover {
  transform: translateY(-6px);
  border-color: var(--line-strong);
  box-shadow: var(--shadow);
}
.card:hover::after { opacity: 1; }
.card-icon {
  font-family: "JetBrains Mono", monospace;
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--accent);
  width: 52px; height: 52px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line-strong);
  border-radius: 12px;
  margin-bottom: 18px;
  background: rgba(0, 212, 255, 0.06);
}
.card h3 {
  font-family: "Space Grotesk", sans-serif;
  font-size: 1.15rem;
  margin-bottom: 12px;
  color: var(--text);
}
.card p { color: var(--text-dim); font-size: 0.95rem; }

/* ===== formula box ===== */
.formula-box {
  margin: 44px 0;
  background: linear-gradient(135deg, rgba(0,212,255,0.05), rgba(79,140,255,0.03));
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  padding: 32px 28px;
  text-align: center;
  position: relative;
}
.formula-box::before {
  content: "";
  position: absolute;
  inset: -1px;
  border-radius: var(--radius);
  padding: 1px;
  background: linear-gradient(135deg, var(--accent), transparent 50%);
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask-composite: exclude;
  opacity: 0.5;
  pointer-events: none;
}
.formula-label {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.72rem;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 16px;
}
.formula {
  font-family: "JetBrains Mono", monospace;
  font-size: clamp(1.1rem, 3vw, 1.6rem);
  color: #fff;
  letter-spacing: 0.5px;
  line-height: 1.6;
}
.formula sup { font-size: 0.7em; color: var(--accent); }
.frac {
  display: inline-flex;
  flex-direction: column;
  vertical-align: middle;
  text-align: center;
  margin: 0 4px;
  font-size: 0.78em;
}
.frac .num { border-bottom: 1px solid var(--accent); padding: 0 8px 2px; }
.frac .den { padding: 2px 8px 0; }
.formula-note {
  margin-top: 16px;
  font-size: 0.85rem;
  color: var(--text-dim);
}

/* ===== before / after ===== */
.before-after {
  display: flex;
  align-items: stretch;
  gap: 16px;
  margin: 40px 0 8px;
  flex-wrap: wrap;
}
.ba-card {
  flex: 1;
  min-width: 240px;
  border-radius: var(--radius);
  padding: 26px 24px;
  border: 1px solid var(--line);
}
.ba-old { background: rgba(255, 122, 69, 0.05); border-color: rgba(255,122,69,0.2); }
.ba-new { background: rgba(0, 212, 255, 0.06); border-color: var(--line-strong); }
.ba-tag {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.72rem;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  margin-bottom: 14px;
}
.ba-old .ba-tag { color: var(--warm); }
.ba-new .ba-tag { color: var(--accent); }
.ba-card p { color: var(--text-dim); font-size: 0.95rem; }
.ba-arrow {
  display: flex;
  align-items: center;
  font-size: 1.8rem;
  color: var(--accent);
  font-family: "JetBrains Mono", monospace;
}

/* ===== ampere visualization ===== */
.ampere-viz {
  margin: 40px 0;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 40px 28px 28px;
  text-align: center;
}
.wire {
  position: relative;
  height: 60px;
  margin: 0 auto;
  max-width: 640px;
}
.wire-line {
  position: absolute;
  top: 50%;
  left: 0; right: 0;
  height: 3px;
  background: linear-gradient(90deg, transparent, var(--accent-2), transparent);
  border-radius: 2px;
  transform: translateY(-50%);
  box-shadow: 0 0 12px var(--accent-glow);
}
.electron-flow {
  position: absolute;
  top: 50%;
  left: 0; right: 0;
  height: 30px;
  transform: translateY(-50%);
}
.electron {
  position: absolute;
  top: 50%;
  width: 14px; height: 14px;
  border-radius: 50%;
  background: radial-gradient(circle at 35% 35%, #fff, var(--accent));
  box-shadow: 0 0 12px var(--accent-glow);
  transform: translate(-50%, -50%);
}
.viz-caption {
  margin-top: 26px;
  font-family: "JetBrains Mono", monospace;
  font-size: 0.85rem;
  color: var(--text-dim);
}

/* ===== timeline ===== */
.timeline {
  position: relative;
  padding-left: 0;
  margin-top: 20px;
}
.timeline::before {
  content: "";
  position: absolute;
  left: 78px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(180deg, var(--accent), var(--accent-2) 50%, transparent);
  opacity: 0.4;
}
.tl-item {
  display: grid;
  grid-template-columns: 78px 1fr;
  gap: 28px;
  padding-bottom: 40px;
  position: relative;
}
.tl-item:last-child { padding-bottom: 0; }
.tl-year {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.85rem;
  color: var(--accent);
  text-align: right;
  padding-top: 4px;
  position: relative;
}
.tl-year::after {
  content: "";
  position: absolute;
  right: -34px;
  top: 10px;
  width: 12px; height: 12px;
  border-radius: 50%;
  background: var(--bg);
  border: 2px solid var(--accent);
  box-shadow: 0 0 12px var(--accent-glow);
}
.tl-body h3 {
  font-family: "Space Grotesk", sans-serif;
  font-size: 1.2rem;
  color: var(--text);
  margin-bottom: 10px;
}
.tl-body p { color: var(--text-dim); font-size: 0.96rem; }

/* ===== steps ===== */
.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 18px;
  margin: 40px 0;
}
.step {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 26px 22px;
  transition: border-color 0.3s, transform 0.3s;
}
.step:hover { border-color: var(--line-strong); transform: translateY(-4px); }
.step-num {
  font-family: "JetBrains Mono", monospace;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
  width: 40px; height: 40px;
  border: 1px solid var(--line-strong);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  background: rgba(0,212,255,0.06);
}
.step h4 {
  font-family: "Space Grotesk", sans-serif;
  font-size: 1.05rem;
  margin-bottom: 8px;
}
.step p { font-size: 0.9rem; color: var(--text-dim); }

/* ===== footer ===== */
.footer {
  padding: 70px 24px 50px;
  text-align: center;
  border-top: 1px solid var(--line);
  background: rgba(5, 7, 15, 0.6);
}
.footer-inner { max-width: 640px; margin: 0 auto; }
.footer-e {
  font-family: "JetBrains Mono", monospace;
  font-size: 1.1rem;
  color: var(--accent);
  margin-bottom: 18px;
  text-shadow: 0 0 30px var(--accent-glow);
}
.footer-text { color: var(--text-dim); font-size: 0.95rem; margin-bottom: 14px; }
.footer-credit {
  font-family: "JetBrains Mono", monospace;
  font-size: 0.75rem;
  color: var(--text-faint);
  letter-spacing: 0.5px;
}

/* ===== scroll reveal ===== */
.reveal {
  opacity: 0;
  transform: translateY(36px);
  transition: opacity 0.8s var(--ease), transform 0.8s var(--ease);
}
.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== responsive ===== */
@media (max-width: 760px) {
  .nav-links { display: none; }
  .nav-inner { padding: 14px 18px; gap: 12px; }
  .brand-num { display: none; }
  .section { padding: 80px 20px; }
  .section-head { flex-wrap: wrap; margin-bottom: 36px; }
  .timeline::before { left: 56px; }
  .tl-item { grid-template-columns: 56px 1fr; gap: 18px; }
  .tl-year::after { right: -24px; }
  .ba-arrow { width: 100%; justify-content: center; transform: rotate(90deg); }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
  .reveal { opacity: 1; transform: none; }
}