/* ───────────────────────────────────────────────
   WowDesign · Swiss minimal system
   ─────────────────────────────────────────────── */

:root {
  --bg: #f5f3ee;
  --fg: #0a0a0a;
  --muted: #6b6b66;
  --line: #d9d6cc;
  --card: #ffffff;
  --accent: oklch(0.65 0.18 30);
  --grid: rgba(10, 10, 10, 0.04);

  --font-sans: "Helvetica Neue", Helvetica, "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;

  --pad-x: clamp(24px, 6vw, 96px);
}

[data-theme="dark"] {
  --bg: #0a0a0a;
  --fg: #f5f3ee;
  --muted: #8a8a85;
  --line: #1f1f1c;
  --card: #141413;
  --grid: rgba(245, 243, 238, 0.04);
}

[data-theme="paper"] {
  --bg: #ffffff;
  --fg: #0a0a0a;
  --muted: #767676;
  --line: #e5e5e5;
  --card: #fafafa;
  --accent: oklch(0.55 0.18 250);
  --grid: rgba(10, 10, 10, 0.03);
}

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

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--fg);
  font-size: 15px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  font-feature-settings: "kern" 1, "ss01" 1;
  letter-spacing: -0.005em;
  min-height: 100vh;
  overflow-x: hidden;
  transition: background 0.3s ease, color 0.3s ease;
}

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

::selection { background: var(--fg); color: var(--bg); }

.grid-bg {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(to right, var(--grid) 1px, transparent 1px),
    linear-gradient(to bottom, var(--grid) 1px, transparent 1px);
  background-size: 96px 96px;
  background-position: 50% 50%;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 80%);
}

.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px var(--pad-x);
  background: color-mix(in oklab, var(--bg) 88%, transparent);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.02em;
  font-weight: 500;
}
.brand .mark {
  width: 22px; height: 22px;
  display: grid;
  place-items: center;
  position: relative;
}
.brand .mark::before {
  content: "";
  position: absolute;
  inset: 0;
  border: 1.5px solid var(--fg);
  border-radius: 50%;
}
.brand .mark::after {
  content: "";
  width: 8px; height: 8px;
  background: var(--accent);
  border-radius: 50%;
}
.brand b { font-weight: 600; }
.brand .tag { color: var(--muted); font-weight: 400; margin-left: 4px; }

.nav {
  display: flex;
  align-items: center;
  gap: 28px;
}
.nav a {
  font-family: var(--font-mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  position: relative;
  padding: 4px 0;
  transition: color 0.2s;
}
.nav a:hover { color: var(--fg); }
.nav a.active { color: var(--fg); }
.nav a.active::after {
  content: "";
  position: absolute;
  left: -10px;
  top: 50%;
  width: 5px; height: 5px;
  background: var(--accent);
  border-radius: 50%;
  transform: translateY(-50%);
}
.nav .num {
  font-size: 10px;
  color: var(--muted);
  margin-right: 4px;
}

.topbar-end {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

.lang-toggle {
  display: flex;
  align-items: center;
  gap: 0;
  border: 1px solid var(--line);
  border-radius: 999px;
  overflow: hidden;
  font-family: var(--font-mono);
  font-size: 11px;
}
.lang-toggle button {
  background: transparent;
  border: 0;
  padding: 6px 12px;
  color: var(--muted);
  cursor: pointer;
  font-family: inherit;
  font-size: inherit;
  letter-spacing: 0.04em;
}
.lang-toggle button.on {
  background: var(--fg);
  color: var(--bg);
}

.nav-burger {
  display: none;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 4px;
  color: var(--fg);
  cursor: pointer;
  font-size: 18px;
  line-height: 1;
  padding: 0;
}
.nav-burger .burger-close { display: none; }
.nav-burger[aria-expanded="true"] .burger-icon { display: none; }
.nav-burger[aria-expanded="true"] .burger-close { display: block; }

main {
  position: relative;
  z-index: 1;
  padding-top: 72px;
}

.page-head {
  padding: clamp(40px, 8vw, 96px) var(--pad-x) clamp(24px, 4vw, 48px);
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
  border-bottom: 1px solid var(--line);
}
.page-head .meta {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  display: flex;
  gap: 22px;
  align-items: center;
}
.page-head .meta .dot {
  width: 6px; height: 6px;
  background: var(--accent);
  border-radius: 50%;
  display: inline-block;
}
.page-head h1 {
  font-size: clamp(48px, 9vw, 132px);
  font-weight: 500;
  line-height: 0.92;
  letter-spacing: -0.04em;
  margin: 0;
  max-width: 14ch;
}
.page-head .lede {
  font-size: clamp(16px, 1.6vw, 20px);
  line-height: 1.45;
  max-width: 56ch;
  color: var(--muted);
  margin-top: 8px;
}

.section {
  padding: clamp(48px, 8vw, 120px) var(--pad-x);
  border-bottom: 1px solid var(--line);
}
.section-head {
  display: grid;
  grid-template-columns: minmax(120px, 200px) 1fr;
  gap: clamp(24px, 4vw, 64px);
  align-items: baseline;
  margin-bottom: clamp(32px, 5vw, 64px);
}
.section-head .label {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}
.section-head h2 {
  font-size: clamp(28px, 4.2vw, 56px);
  font-weight: 500;
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin: 0;
  max-width: 22ch;
}

.rule {
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--muted);
  letter-spacing: 0.1em;
}
.rule::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--line);
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 22px;
  border: 1px solid var(--fg);
  background: var(--fg);
  color: var(--bg);
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  cursor: pointer;
  transition: transform 0.2s, background 0.2s;
}
.btn:hover { transform: translateY(-1px); }
.btn.ghost {
  background: transparent;
  color: var(--fg);
}
.btn .arrow {
  display: inline-block;
  transition: transform 0.2s;
}
.btn:hover .arrow { transform: translateX(4px); }

footer.foot {
  padding: 64px var(--pad-x) 32px;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: clamp(24px, 4vw, 64px);
  border-top: 1px solid var(--line);
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
}
footer.foot h4 {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-weight: 500;
  color: var(--fg);
  margin: 0 0 16px;
}
footer.foot a { display: block; padding: 4px 0; }
footer.foot a:hover { color: var(--fg); }
footer.foot .colophon {
  grid-column: 1 / -1;
  padding-top: 32px;
  margin-top: 32px;
  border-top: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  font-size: 10px;
}

.tweaks-fab {
  position: fixed;
  bottom: 20px; right: 20px;
  width: 44px; height: 44px;
  border-radius: 50%;
  background: var(--fg);
  color: var(--bg);
  border: 0;
  cursor: pointer;
  z-index: 80;
  display: none;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 16px;
  box-shadow: 0 6px 20px rgba(0,0,0,0.18);
}
.tweaks-fab.show { display: flex; }
.tweaks-panel {
  position: fixed;
  bottom: 76px; right: 20px;
  width: 280px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 18px;
  z-index: 90;
  display: none;
  font-family: var(--font-mono);
  font-size: 12px;
  box-shadow: 0 12px 32px rgba(0,0,0,0.12);
}
.tweaks-panel.show { display: block; }
.tweaks-panel h5 {
  margin: 0 0 14px;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.tweaks-panel h5 .close { cursor: pointer; color: var(--muted); }
.tweaks-panel .group { margin-bottom: 16px; }
.tweaks-panel .group:last-child { margin-bottom: 0; }
.tweaks-panel label {
  display: block;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 10px;
  margin-bottom: 6px;
}
.tweaks-panel .segment {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 1fr;
  border: 1px solid var(--line);
  border-radius: 6px;
  overflow: hidden;
}
.tweaks-panel .segment button {
  background: transparent;
  border: 0;
  padding: 8px 6px;
  font-family: inherit;
  font-size: 11px;
  color: var(--muted);
  cursor: pointer;
  border-right: 1px solid var(--line);
}
.tweaks-panel .segment button:last-child { border-right: 0; }
.tweaks-panel .segment button.on {
  background: var(--fg);
  color: var(--bg);
}

@media (max-width: 760px) {
  .nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    background: color-mix(in oklab, var(--bg) 96%, transparent);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--line);
    padding: 8px var(--pad-x) 16px;
  }
  .nav.open { display: flex; }
  .nav a {
    width: 100%;
    padding: 12px 0;
    border-bottom: 1px solid var(--line);
    font-size: 13px;
  }
  .nav a:last-child { border-bottom: 0; }
  .nav .num { display: none; }
  .nav-burger { display: flex; }
  .section-head { grid-template-columns: 1fr; }
  footer.foot { grid-template-columns: 1fr 1fr; }
}