/* ============================================================
   AI Skills Hub — CSS Reset & Design Tokens
   ============================================================ */

:root {
  --hue: 260;
  --color-primary: hsl(var(--hue), 65%, 55%);
  --color-primary-light: hsl(var(--hue), 65%, 92%);
  --color-primary-dark: hsl(var(--hue), 65%, 35%);
  --color-accent: hsl(170, 80%, 45%);
  --color-warning: hsl(35, 90%, 50%);
  --color-danger: hsl(0, 70%, 55%);

  --surface-ground: hsl(var(--hue), 10%, 96%);
  --surface-card: hsl(0, 0%, 100%);
  --surface-elevated: hsl(0, 0%, 100%);

  --text-primary: hsl(var(--hue), 10%, 15%);
  --text-secondary: hsl(var(--hue), 8%, 45%);
  --text-tertiary: hsl(var(--hue), 5%, 65%);

  --space-xs: 4px; --space-sm: 8px; --space-md: 16px;
  --space-lg: 24px; --space-xl: 32px; --space-2xl: 48px;

  --font-sans: "Noto Sans SC", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", monospace;
  --text-xs: 0.75rem; --text-sm: 0.875rem; --text-base: 1rem;
  --text-lg: 1.125rem; --text-xl: 1.25rem; --text-2xl: 1.5rem; --text-3xl: 1.875rem;

  --radius-sm: 6px; --radius-md: 10px; --radius-lg: 16px; --radius-full: 9999px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);

  --header-h: 56px; --bottom-nav-h: 64px;
  --content-max: 800px; --card-min: 160px;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --dur-fast: 150ms; --dur-normal: 250ms; --dur-slow: 400ms;
}

/* Dark mode */
[data-theme="dark"] {
  --surface-ground: hsl(var(--hue), 10%, 8%);
  --surface-card: hsl(var(--hue), 10%, 14%);
  --surface-elevated: hsl(var(--hue), 10%, 18%);
  --text-primary: hsl(var(--hue), 10%, 90%);
  --text-secondary: hsl(var(--hue), 8%, 65%);
  --text-tertiary: hsl(var(--hue), 5%, 50%);
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.4);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.5);
}

/* Base reset */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; font-size: var(--text-base); }

body {
  font-family: var(--font-sans);
  color: var(--text-primary);
  background: var(--surface-ground);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  overscroll-behavior: none;
}

img { max-width: 100%; height: auto; display: block; }
a { color: var(--color-primary); text-decoration: none; }
ul { list-style: none; }
button { cursor: pointer; font: inherit; border: none; background: none; color: inherit; }
input { font: inherit; color: inherit; border: 1px solid hsl(var(--hue), 5%, 85%); border-radius: var(--radius-sm); padding: 10px 14px; width: 100%; }
input:focus { outline: 2px solid var(--color-primary); outline-offset: -1px; }

h1 { font-size: var(--text-3xl); }
h2 { font-size: var(--text-2xl); }
h3 { font-size: var(--text-xl); }
h4 { font-size: var(--text-lg); }

/* Skeleton loading */
@keyframes shimmer {
  0% { background-position: -200px 0; }
  100% { background-position: 200px 0; }
}
.skeleton { background: linear-gradient(90deg, var(--surface-ground) 25%, hsl(var(--hue),10%,90%) 50%, var(--surface-ground) 75%); background-size: 400px 100%; animation: shimmer 1.5s infinite; border-radius: var(--radius-sm); }
.skeleton--text { height: 14px; margin-bottom: 8px; }
.skeleton--title { height: 20px; width: 60%; margin-bottom: 12px; }
.skeleton--circle { border-radius: 50%; }
.skeleton-card { background: var(--surface-card); border-radius: var(--radius-md); padding: var(--space-md); }

/* Accessibility */
:focus-visible { outline: 2px solid var(--color-primary); outline-offset: 2px; }

/* Scrollbar */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-thumb { background: var(--text-tertiary); border-radius: 3px; }

@media (min-width: 768px) { :root { --content-max: 720px; } }
@media (min-width: 1024px) { :root { --content-max: 960px; --header-h: 64px; } }