/* ============================================================
   BTG @ PKNU — Design System / Colors & Type
   Brain Theory Group, Pukyong National University
   ============================================================ */

/* ---- Fonts (local) --------------------------------------- */
@font-face {
  font-family: 'Inter';
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url('fonts/Inter-Variable.woff2') format('woff2-variations');
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url('fonts/JetBrainsMono-400.woff2') format('woff2');
}
@font-face {
  font-family: 'JetBrains Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url('fonts/JetBrainsMono-500.woff2') format('woff2');
}

/* ---- Tokens ---------------------------------------------- */
:root {
  /* Font families */
  --font-display: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;

  /* Color — ground & ink */
  --paper: oklch(98% 0.005 90);       /* warm off-white page */
  --paper-2: oklch(96% 0.008 90);     /* subtle surface elevation */
  --ink: oklch(18% 0.02 260);          /* deep near-black w/ navy hint */
  --ink-soft: oklch(24% 0.03 260);

  /* Color — brand */
  --btg-navy: oklch(32% 0.11 255);     /* primary brand (PKNU-nod) */
  --btg-navy-hover: oklch(28% 0.12 255);
  --btg-navy-soft: oklch(90% 0.03 255);

  /* Color — neural signal accents (data-vis inspired) */
  --neural-magenta: oklch(58% 0.22 340);
  --neural-cyan: oklch(70% 0.13 205);
  --neural-amber: oklch(72% 0.14 70);
  --neural-violet: oklch(52% 0.18 295);

  /* Color — semantic foreground */
  --fg-1: var(--ink);                                 /* primary text */
  --fg-2: oklch(45% 0.02 260);                        /* secondary text (meta) */
  --fg-3: oklch(62% 0.015 260);                       /* tertiary (captions, hint) */
  --fg-inv: var(--paper);                             /* on-dark text */

  /* Color — semantic background/surface */
  --bg: var(--paper);
  --surface: var(--paper);
  --surface-2: var(--paper-2);
  --surface-inv: var(--ink);

  /* Color — line */
  --border: oklch(88% 0.008 260);
  --border-strong: oklch(78% 0.012 260);
  --divider: oklch(92% 0.006 260);

  /* Color — feedback (used sparingly) */
  --success: oklch(58% 0.12 155);
  --warning: oklch(72% 0.15 75);
  --danger: oklch(58% 0.19 25);

  /* Radii */
  --r-xs: 2px;
  --r-sm: 4px;
  --r-md: 8px;
  --r-lg: 16px;
  --r-xl: 24px;
  --r-pill: 999px;

  /* Spacing — 4px baseline */
  --s-0: 0;
  --s-1: 4px;
  --s-2: 8px;
  --s-3: 12px;
  --s-4: 16px;
  --s-5: 24px;
  --s-6: 32px;
  --s-7: 48px;
  --s-8: 64px;
  --s-9: 96px;
  --s-10: 128px;

  /* Type sizes (modular scale 1.25 anchored at 16px) */
  --t-mono: 12px;
  --t-xs: 13px;
  --t-sm: 15px;
  --t-body: 17px;
  --t-lg: 20px;
  --t-h4: 24px;
  --t-h3: 32px;
  --t-h2: 40px;
  --t-h1: 56px;
  --t-display: 88px;

  /* Line-heights */
  --lh-display: 1.02;
  --lh-heading: 1.15;
  --lh-body: 1.65;
  --lh-tight: 1.25;

  /* Weights */
  --w-regular: 400;
  --w-medium: 500;
  --w-semibold: 600;
  --w-bold: 700;

  /* Letter-spacing */
  --ls-display: -0.02em;
  --ls-heading: -0.01em;
  --ls-body: 0;
  --ls-mono: 0;
  --ls-caps: 0.08em;

  /* Shadows — restrained */
  --shadow-1: 0 1px 2px oklch(18% 0.02 260 / 0.06);
  --shadow-2: 0 12px 32px -12px oklch(18% 0.02 260 / 0.16);

  /* Motion */
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --dur-fast: 150ms;
  --dur: 240ms;
  --dur-slow: 400ms;

  /* Layout */
  --max-w: 1120px;
  --max-w-prose: 720px;

  /* Focus ring */
  --ring: 0 0 0 3px oklch(58% 0.22 340 / 0.24);
}

/* ---- Base ------------------------------------------------ */
html, body {
  background: var(--bg);
  color: var(--fg-1);
  font-family: var(--font-body);
  font-size: var(--t-body);
  line-height: var(--lh-body);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  font-feature-settings: 'ss01', 'cv11';
}

* { box-sizing: border-box; }

::selection { background: oklch(58% 0.22 340 / 0.22); color: var(--fg-1); }

/* ---- Semantic type -------------------------------------- */
.display, h1.display {
  font-family: var(--font-display);
  font-size: var(--t-display);
  line-height: var(--lh-display);
  letter-spacing: var(--ls-display);
  font-weight: 600;
  color: var(--fg-1);
  margin: 0;
}

h1, .h1 {
  font-family: var(--font-display);
  font-size: var(--t-h1);
  line-height: var(--lh-heading);
  letter-spacing: var(--ls-heading);
  font-weight: 600;
  margin: 0;
}

h2, .h2 {
  font-family: var(--font-display);
  font-size: var(--t-h2);
  line-height: var(--lh-heading);
  letter-spacing: var(--ls-heading);
  font-weight: 600;
  margin: 0;
}

h3, .h3 {
  font-family: var(--font-display);
  font-size: var(--t-h3);
  line-height: var(--lh-tight);
  letter-spacing: -0.005em;
  font-weight: 600;
  margin: 0;
}

h4, .h4 {
  font-family: var(--font-body);
  font-size: var(--t-h4);
  line-height: var(--lh-tight);
  font-weight: 600;
  margin: 0;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--t-mono);
  text-transform: uppercase;
  letter-spacing: var(--ls-caps);
  color: var(--fg-2);
  font-weight: 500;
}

p, .p {
  font-size: var(--t-body);
  line-height: var(--lh-body);
  color: var(--fg-1);
  margin: 0;
}

.meta, small {
  font-size: var(--t-xs);
  color: var(--fg-2);
  line-height: 1.5;
}

.mono, code, kbd, pre {
  font-family: var(--font-mono);
  font-size: 0.92em;
  letter-spacing: var(--ls-mono);
}

.lead {
  font-family: var(--font-body);
  font-size: var(--t-h4);
  line-height: 1.45;
  font-weight: 400;
  color: var(--ink-soft);
}

a {
  color: var(--fg-1);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  text-decoration-color: var(--border-strong);
  transition: text-decoration-color var(--dur-fast) var(--ease),
              text-decoration-thickness var(--dur-fast) var(--ease);
}
a:hover {
  text-decoration-thickness: 2px;
  text-decoration-color: var(--neural-magenta);
}

/* ---- Utility --------------------------------------------- */
.container { max-width: var(--max-w); margin-inline: auto; padding-inline: var(--s-5); }
.prose { max-width: var(--max-w-prose); }
.hairline { border: 1px solid var(--border); }
.rule { height: 1px; background: var(--divider); border: 0; }

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: 0ms !important;
    animation-duration: 0ms !important;
  }
}