:root {
  /* UI-1 foundation baseline. Values remain candidates for the UI-3 benchmark. */
  --canvas: #080b10;
  --workspace: #0e131b;
  --surface-functional: #131a24;
  --surface-elevated: #192230;
  --surface-overlay: #1d2735;
  --overlay-backdrop: rgba(3, 6, 10, 0.72);

  --text-primary: #f2f5f8;
  --text-secondary: #c2cad4;
  --text-muted: #8994a3;
  --text-disabled: #667180;
  --text-inverse: #10151d;

  --border-subtle: rgba(209, 220, 231, 0.1);
  --border-functional: rgba(209, 220, 231, 0.17);
  --border-strong: rgba(214, 227, 240, 0.28);
  --accent: #8db7d5;
  --accent-strong: #b9d7ea;
  --focus-ring: rgba(141, 183, 213, 0.72);

  --status-neutral: #8e9baa;
  --status-info: #8db7d5;
  --status-attention: #c8a971;
  --status-success: #8eae9a;
  --status-warning: #d0a86a;
  --status-danger: #d18d83;
  --status-selected: #a7c8df;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 22px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --elevation-base: none;
  --elevation-elevated: 0 10px 28px rgba(0, 0, 0, 0.18);
  --elevation-overlay: 0 22px 56px rgba(0, 0, 0, 0.36);

  --type-display: clamp(1.75rem, 2vw, 2.4rem);
  --type-page: 1.5rem;
  --type-section: 1.125rem;
  --type-panel: 0.9375rem;
  --type-body: 0.875rem;
  --type-compact: 0.8125rem;
  --type-meta: 0.75rem;
  --type-label: 0.6875rem;
  --line-title: 1.18;
  --line-body: 1.55;
  --line-compact: 1.4;

  /* Transitional aliases: preserve existing component contracts during UI-1. */
  --if-night-navy: var(--canvas);
  --if-cinema-white: var(--text-primary);
  --if-aurora-cyan: var(--accent);
  --if-shell-glass: color-mix(in srgb, var(--workspace) 84%, transparent);
  --if-shell-border: var(--border-functional);
  --font-geist-sans: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --font-geist-mono: Consolas, "Courier New", monospace;
  --if-fog: var(--workspace);
  --if-paper: var(--surface-functional);
  --if-ink: var(--text-primary);
  --if-line: var(--border-functional);
  --if-ice: var(--accent);
  --if-warm: var(--status-attention);
  --if-glass-bg: color-mix(in srgb, var(--surface-functional) 92%, transparent);
  --if-glass-bg-strong: var(--surface-elevated);
  --if-glass-border: var(--border-functional);
  --if-glass-highlight: rgba(255, 255, 255, 0.06);
  --if-glass-shadow: var(--elevation-elevated);
  --if-glass-blur: 8px;
  --if-glass-saturate: 1;
  --if-shell-shadow: var(--elevation-elevated);
  --background: var(--canvas);
  --foreground: var(--text-primary);
}
* { box-sizing: border-box; }

html { color-scheme: dark; }

body {
  margin: 0;
  min-width: 0;
  background: var(--canvas);
  color: var(--text-primary);
  font-family: var(--font-geist-sans);
  font-size: 1rem;
  line-height: 1.6;
}

::selection { background: var(--accent-strong); color: var(--text-inverse); }

a { color: var(--accent-strong); text-underline-offset: 0.25em; }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; }
.wrap { width: min(100% - 3rem, 70rem); margin-inline: auto; }

.skip-link {
  position: absolute;
  left: 1rem;
  top: 1rem;
  z-index: 1;
  padding: 0.5rem 0.75rem;
  background: var(--surface-elevated);
}
.skip-link:not(:focus) { clip-path: inset(50%); }

.site-header { background: var(--workspace); border-bottom: 1px solid var(--border-functional); }
.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 1rem 2rem;
  padding-block: 1rem;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  color: var(--text-primary);
  font-weight: 700;
  text-decoration: none;
}
.brand-cn { margin-inline-start: 0.3rem; color: var(--text-secondary); font-weight: 400; }
nav { display: flex; flex-wrap: wrap; gap: 0.4rem 1.1rem; }
nav a { padding-block: 0.2rem; color: var(--text-secondary); text-decoration: none; }
nav a:hover, nav a[aria-current="page"] { color: var(--accent-strong); text-decoration: underline; }

main { padding-block: clamp(2.5rem, 7vw, 6rem); }
.document { max-width: 52rem; }
.intro { padding-bottom: clamp(1.75rem, 4vw, 3.25rem); }
h1, h2, p { margin: 0; }
h1 {
  max-width: 20ch;
  font-size: clamp(2.25rem, 5.4vw, 5rem);
  line-height: 1.05;
  letter-spacing: -0.035em;
  text-wrap: balance;
}
.document h1 { font-size: clamp(2.1rem, 4.5vw, 3.75rem); }
.intro p { margin-top: 1.25rem; max-width: 65ch; font-size: clamp(1.05rem, 2vw, 1.25rem); }
p { color: var(--text-secondary); max-width: 70ch; }
.sections { border-top: 1px solid var(--border-functional); }
.sections section { padding-block: 1.25rem; border-bottom: 1px solid var(--border-functional); }
.home .sections section { display: grid; grid-template-columns: minmax(12rem, 1fr) 2fr; gap: 0.5rem 2rem; }
h2 { font-size: 1.125rem; line-height: 1.4; }
.document h2 { margin-bottom: 0.375rem; }

@media (max-width: 42rem) {
  .wrap { width: min(100% - 2rem, 70rem); }
  .home .sections section { grid-template-columns: 1fr; }
  .header-inner { align-items: flex-start; flex-direction: column; }
}