/* ============================================================
   Pi-Dimension site kit — tokens + hub components
   ------------------------------------------------------------
   Derived from Pi-Dimension-Design-System/colors_and_type.css.
   One ink (#11468C), paper white, graphite text, hairline rules.
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+KR:wght@100..900&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+KR:wght@400;500;600;700&display=swap');
@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+Math&display=swap');

@font-face {
  font-family: 'D2Coding';
  src: url('fonts/D2Coding.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: 'D2Coding';
  src: url('fonts/D2CodingBold.woff2') format('woff2');
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

:root {
  /* ---------- brand ink ---------- */
  --pi-ink-900: #07254E;
  --pi-ink-800: #0D3672;
  --pi-ink-700: #11468C;
  --pi-ink-600: #2A5FA6;
  --pi-ink-500: #4F82C2;
  --pi-ink-400: #7AA3D5;
  --pi-ink-300: #A8C2E2;
  --pi-ink-200: #D2DEEE;
  --pi-ink-100: #E9EFF7;
  --pi-ink-50:  #F4F7FB;

  /* ---------- paper & graphite ---------- */
  --pi-paper:   #FAFBFC;
  --pi-paper-2: #F4F6F9;
  --pi-paper-3: #ECEFF3;
  --pi-rule:    #E4E8EE;
  --pi-rule-2:  #D4DAE3;

  --pi-graphite-100: #C8CDD5;
  --pi-graphite-200: #A2A8B3;
  --pi-graphite-300: #767D89;
  --pi-graphite-400: #4F5663;
  --pi-graphite-500: #2C323C;
  --pi-graphite-600: #1A1E26;
  --pi-graphite-700: #0E1117;

  --pi-white: #FFFFFF;

  /* ---------- supporting materials ---------- */
  --c-iron:    #3F4856; --c-iron-soft:    #E5E8ED;
  --c-copper:  #A75928; --c-copper-soft:  #F2DECF;
  --c-brass:   #949A33; --c-brass-soft:   #EFF2C8;
  --c-walnut:  #5A3A1E; --c-walnut-soft:  #E5D6C4;
  --c-latte:   #D2B594; --c-latte-soft:   #F1E7DB;
  --c-moss:    #506A47; --c-moss-soft:    #E1E7DC;
  --c-citrine: #CC9528; --c-citrine-soft: #F8E4BD;
  --c-ruby:    #A8273B; --c-ruby-soft:    #F1D3D9;
  --c-opal:    #8472A0; --c-opal-soft:    #ECE5F1;

  --pi-success: #506A47; --pi-success-bg: #E1E7DC;
  --pi-warning: #CC9528; --pi-warning-bg: #F8E4BD;
  --pi-danger:  #A8273B; --pi-danger-bg:  #F1D3D9;
  --pi-info:    var(--pi-ink-700);
  --pi-info-bg: var(--pi-ink-50);

  /* ---------- semantic ---------- */
  --bg:           var(--pi-paper);
  --bg-elevated:  var(--pi-white);
  --bg-sunken:    var(--pi-paper-2);
  --bg-inverse:   var(--pi-graphite-700);

  --fg:      var(--pi-graphite-600);
  --fg-1:    var(--pi-graphite-600);
  --fg-2:    var(--pi-graphite-500);
  --fg-3:    var(--pi-graphite-400);
  --fg-4:    var(--pi-graphite-300);
  --fg-muted:var(--pi-graphite-200);
  --fg-on-ink: var(--pi-paper);

  --accent:       var(--pi-ink-700);
  --accent-hover: var(--pi-ink-800);
  --accent-press: var(--pi-ink-900);
  --accent-soft:  var(--pi-ink-50);
  --accent-fg:    var(--pi-white);

  --rule:        var(--pi-rule);
  --rule-strong: var(--pi-rule-2);
  --focus-ring:  var(--pi-ink-500);

  /* ---------- type ---------- */
  --font-sans: 'Noto Sans KR', -apple-system, BlinkMacSystemFont,
               'Apple SD Gothic Neo', 'Helvetica Neue', Arial, sans-serif;
  --font-serif: 'Noto Serif KR', 'Apple SD Gothic Neo', 'Iowan Old Style',
                Georgia, 'Times New Roman', serif;
  --font-mono: 'D2Coding', ui-monospace, 'SF Mono', Menlo, Consolas, monospace;
  --font-math: 'Noto Sans Math', 'STIX Two Math', 'Cambria Math', serif;

  --step--2: 0.694rem;
  --step--1: 0.833rem;
  --step-0:  1rem;
  --step-1:  1.25rem;
  --step-2:  1.563rem;
  --step-3:  1.953rem;
  --step-4:  2.441rem;
  --step-5:  3.052rem;
  --step-6:  3.815rem;
  --step-7:  4.768rem;

  --leading-tight: 1.1;
  --leading-snug: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.65;

  --tracking-tight: -0.02em;
  --tracking-snug: -0.01em;
  --tracking-wide: 0.04em;
  --tracking-mono: 0.08em;

  /* ---------- spacing / radii / shadow / motion ---------- */
  --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; --s-11: 192px;

  --gutter: clamp(16px, 3vw, 48px);
  --column-max: 72ch;
  --frame-max: 1360px;

  --r-1: 2px; --r-2: 4px; --r-3: 8px; --r-4: 12px; --r-pill: 999px;

  --shadow-1: 0 1px 0 rgba(17, 70, 140, 0.04), 0 1px 2px rgba(17, 70, 140, 0.06);
  --shadow-2: 0 1px 0 rgba(17, 70, 140, 0.04), 0 4px 12px -2px rgba(17, 70, 140, 0.08);
  --shadow-3: 0 2px 0 rgba(17, 70, 140, 0.03), 0 12px 32px -6px rgba(17, 70, 140, 0.12);
  --shadow-focus: 0 0 0 3px rgba(17, 70, 140, 0.18);

  --ease-out: cubic-bezier(0.22, 0.61, 0.36, 1);
  --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
  --dur-fast: 120ms;
  --dur-base: 200ms;
  --dur-slow: 360ms;
}

/* ============================================================
   Base
   ============================================================ */

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--step-0);
  line-height: var(--leading-relaxed);
  color: var(--fg-2);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 { color: var(--fg-1); margin: 0; }
p { margin: 0; }

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--dur-fast) var(--ease-out);
}
a:hover { color: var(--accent-hover); }

:focus-visible {
  outline: none;
  box-shadow: var(--shadow-focus);
  border-radius: var(--r-1);
}

::selection { background: var(--pi-ink-200); }

/* ============================================================
   Type utilities
   ============================================================ */

.pi-eyebrow {
  font-family: var(--font-mono);
  font-size: var(--step--1);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-3);
}

.pi-caption {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-4);
}

.pi-math { font-family: var(--font-math); }

/* ============================================================
   Frame
   ============================================================ */

.pi-frame {
  max-width: var(--frame-max);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

/* ============================================================
   Top bar — sticky, paper blur, single hairline
   ============================================================ */

.pi-topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(250, 251, 252, 0.7);
  -webkit-backdrop-filter: blur(12px);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rule);
}

.pi-topbar-inner {
  max-width: var(--frame-max);
  margin: 0 auto;
  padding: var(--s-4) var(--gutter);
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-5);
}

.pi-wordmark {
  display: inline-flex;
  align-items: baseline;
  gap: var(--s-3);
  color: var(--fg-1);
}
.pi-wordmark:hover { color: var(--fg-1); }

.pi-wordmark .glyph {
  font-family: var(--font-math);
  font-size: var(--step-1);
  color: var(--accent);
  line-height: 1;
}

.pi-wordmark .name {
  font-family: var(--font-mono);
  font-size: var(--step--1);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-2);
}

.pi-topbar-links {
  display: flex;
  align-items: baseline;
  gap: var(--s-5);
}

.pi-topbar-links a {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-3);
}
.pi-topbar-links a:hover { color: var(--accent); }

/* ============================================================
   Hero
   ============================================================ */

.pi-hero {
  position: relative;
  padding: clamp(64px, 8vw, 96px) 0 clamp(32px, 4vw, 56px);
}

.pi-hero::before {
  /* single quiet ink wash — the one allowed background gesture */
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 640px 320px at 18% 0%,
              rgba(17, 70, 140, 0.06), transparent 70%);
  pointer-events: none;
}

.pi-hero > * { position: relative; }

.pi-hero .pi-eyebrow { margin-bottom: var(--s-4); }

.pi-hero-title {
  font-family: var(--font-serif);
  font-weight: 500;
  font-size: clamp(var(--step-4), 5vw, var(--step-6));
  line-height: var(--leading-tight);
  letter-spacing: var(--tracking-tight);
  max-width: 22ch;
}

.pi-hero-lead {
  margin-top: var(--s-5);
  font-size: var(--step-1);
  line-height: var(--leading-relaxed);
  color: var(--fg-3);
  max-width: 46ch;
}

.pi-hero-meta {
  margin-top: var(--s-6);
  display: flex;
  flex-wrap: wrap;
  gap: var(--s-2) var(--s-4);
}

/* ============================================================
   Sections
   ============================================================ */

.pi-section {
  padding: 0;
  margin-top: clamp(56px, 6vw, 80px);
}

.pi-section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-4);
  padding-bottom: var(--s-4);
  border-bottom: 1px solid var(--rule);
  margin-bottom: var(--s-6);
}

.pi-section-head h2 {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: var(--step-2);
  letter-spacing: var(--tracking-snug);
}

.pi-section-head .count {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  color: var(--fg-4);
}

/* ============================================================
   Cards — hairline over box, ink accents only
   ============================================================ */

.pi-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 320px), 1fr));
  gap: clamp(16px, 2vw, 24px);
}

.pi-card {
  display: flex;
  flex-direction: column;
  gap: var(--s-3);
  background: var(--bg-elevated);
  border: 1px solid var(--rule);
  border-radius: var(--r-3);
  padding: clamp(20px, 2.25vw, 28px);
  color: var(--fg-2);
  transition: box-shadow var(--dur-base) var(--ease-out),
              transform var(--dur-base) var(--ease-out),
              border-color var(--dur-base) var(--ease-out);
}

a.pi-card:hover {
  color: var(--fg-2);
  border-color: var(--rule-strong);
  box-shadow: var(--shadow-2);
  transform: translateY(-1px);
}

.pi-card-top {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-3);
}

.pi-card .glyph {
  font-family: var(--font-math);
  font-size: var(--step-2);
  line-height: 1;
  color: var(--accent);
}

.pi-card h3 {
  font-size: var(--step-1);
  font-weight: 600;
  letter-spacing: var(--tracking-snug);
  line-height: var(--leading-snug);
}

.pi-card p {
  font-size: var(--step--1);
  line-height: var(--leading-normal);
  color: var(--fg-3);
  max-width: 64ch;
}

.pi-card .go {
  margin-top: auto;
  padding-top: var(--s-3);
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--accent);
}

a.pi-card:hover .go { color: var(--accent-hover); }

/* wide card — spans the grid */
.pi-card--wide { grid-column: 1 / -1; }

/* ============================================================
   Tags
   ============================================================ */

.pi-tag {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-3);
  background: var(--bg-sunken);
  border: 1px solid var(--rule);
  border-radius: var(--r-1);
  padding: 2px var(--s-2);
}

.pi-tag--ink { color: var(--accent); background: var(--accent-soft); border-color: var(--pi-ink-200); }

/* ============================================================
   List rows — for quiet secondary indexes
   ============================================================ */

.pi-rows { display: flex; flex-direction: column; }

.pi-row {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-4);
  padding: var(--s-4) var(--s-1);
  border-bottom: 1px solid var(--rule);
  color: var(--fg-2);
}
.pi-row:hover { color: var(--accent); background: var(--accent-soft); }
.pi-row .title { font-weight: 500; }
.pi-row .note {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: var(--tracking-mono);
  text-transform: uppercase;
  color: var(--fg-4);
  white-space: nowrap;
}

/* ============================================================
   Buttons
   ============================================================ */

.pi-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  font-family: var(--font-sans);
  font-size: var(--step--1);
  font-weight: 500;
  color: var(--accent-fg);
  background: var(--accent);
  border: 1px solid var(--accent);
  border-radius: var(--r-2);
  padding: var(--s-2) var(--s-4);
  cursor: pointer;
  transition: background var(--dur-base) var(--ease-out);
}
.pi-btn:hover { background: var(--accent-hover); color: var(--accent-fg); }
.pi-btn:active { background: var(--accent-press); transform: translateY(1px); }

.pi-btn--ghost {
  color: var(--accent);
  background: transparent;
  border-color: var(--pi-ink-200);
}
.pi-btn--ghost:hover { background: var(--accent-soft); color: var(--accent-hover); }

/* ============================================================
   Footer
   ============================================================ */

.pi-footer {
  border-top: 1px solid var(--rule);
  padding: var(--s-6) 0 var(--s-8);
  margin-top: var(--s-9);
}

.pi-footer-inner {
  max-width: var(--frame-max);
  margin: 0 auto;
  padding: 0 var(--gutter);
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s-3) var(--s-5);
}

.pi-footer .pi-caption a { color: var(--fg-4); }
.pi-footer .pi-caption a:hover { color: var(--accent); }

@media (max-width: 640px) {
  .pi-topbar-inner {
    align-items: center;
    gap: var(--s-3);
  }

  .pi-wordmark .name {
    font-size: 0.72rem;
    letter-spacing: 0.04em;
  }

  .pi-topbar-links a {
    font-size: 0.65rem;
    letter-spacing: 0.04em;
  }

  .pi-section-head {
    align-items: flex-start;
  }

  .pi-row {
    align-items: flex-start;
  }
}

/* ============================================================
   Reduced motion
   ============================================================ */

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation: none !important;
    transition: none !important;
  }
  html { scroll-behavior: auto; }
}