/* ===== DESIGN TOKENS ===== */
:root {
  --text-xs:   clamp(0.75rem,  0.7rem  + 0.25vw, 0.875rem);
  --text-sm:   clamp(0.875rem, 0.8rem  + 0.35vw, 1rem);
  --text-base: clamp(1rem,     0.95rem + 0.25vw, 1.125rem);
  --text-lg:   clamp(1.125rem, 1rem    + 0.75vw, 1.5rem);
  --text-xl:   clamp(1.5rem,   1.2rem  + 1.25vw, 2.25rem);
  --text-2xl:  clamp(2rem,     1.2rem  + 2.5vw,  3.5rem);
  --text-3xl:  clamp(2.5rem,   1rem    + 4vw,    5rem);

  --space-1:  0.25rem;
  --space-2:  0.5rem;
  --space-3:  0.75rem;
  --space-4:  1rem;
  --space-5:  1.25rem;
  --space-6:  1.5rem;
  --space-8:  2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  --font-display: 'Cabinet Grotesk', 'Arial Black', sans-serif;
  --font-body: 'General Sans', 'Helvetica Neue', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);
  --content-wide: 1200px;
}

/* Light theme */
:root, [data-theme="light"] {
  --color-bg: #f5f3ef;
  --color-surface: #ffffff;
  --color-surface-2: #faf9f7;
  --color-surface-offset: #eceae5;
  --color-border: #d8d4cc;
  --color-divider: #e4e1db;
  --color-text: #1a1815;
  --color-text-muted: #6b6860;
  --color-text-faint: #a9a69e;
  --color-primary: #5046e5;
  --color-primary-hover: #3d35c5;
  --color-primary-light: #ededfc;

  --color-cat-llm: #5046e5;
  --color-cat-coding: #0ea5e9;
  --color-cat-image: #e84393;
  --color-cat-open-source: #10b981;
  --color-cat-agents: #f59e0b;
  --color-cat-industry: #6366f1;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.12);

  --timeline-line: #d8d4cc;
  --timeline-dot-bg: #ffffff;
}

/* Dark theme */
[data-theme="dark"] {
  --color-bg: #0f0e0d;
  --color-surface: #1a1918;
  --color-surface-2: #222120;
  --color-surface-offset: #161514;
  --color-border: #2e2d2b;
  --color-divider: #252423;
  --color-text: #e4e2de;
  --color-text-muted: #8a877f;
  --color-text-faint: #5a5752;
  --color-primary: #7c73ff;
  --color-primary-hover: #9b94ff;
  --color-primary-light: #1e1c3a;

  --color-cat-llm: #7c73ff;
  --color-cat-coding: #38bdf8;
  --color-cat-image: #f472b6;
  --color-cat-open-source: #34d399;
  --color-cat-agents: #fbbf24;
  --color-cat-industry: #818cf8;

  --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
  --shadow-lg: 0 12px 40px rgba(0,0,0,0.5);

  --timeline-line: #2e2d2b;
  --timeline-dot-bg: #1a1918;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --color-bg: #0f0e0d;
    --color-surface: #1a1918;
    --color-surface-2: #222120;
    --color-surface-offset: #161514;
    --color-border: #2e2d2b;
    --color-divider: #252423;
    --color-text: #e4e2de;
    --color-text-muted: #8a877f;
    --color-text-faint: #5a5752;
    --color-primary: #7c73ff;
    --color-primary-hover: #9b94ff;
    --color-primary-light: #1e1c3a;
    --color-cat-llm: #7c73ff;
    --color-cat-coding: #38bdf8;
    --color-cat-image: #f472b6;
    --color-cat-open-source: #34d399;
    --color-cat-agents: #fbbf24;
    --color-cat-industry: #818cf8;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
    --shadow-lg: 0 12px 40px rgba(0,0,0,0.5);
    --timeline-line: #2e2d2b;
    --timeline-dot-bg: #1a1918;
  }
}

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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  min-height: 100dvh;
  line-height: 1.6;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-text);
  background-color: var(--color-bg);
}

img, picture, video, canvas, svg { display: block; max-width: 100%; height: auto; }
button { cursor: pointer; background: none; border: none; font: inherit; color: inherit; }
a { color: var(--color-primary); text-decoration: none; }
a:hover { color: var(--color-primary-hover); }

h1, h2, h3, h4 { line-height: 1.15; }
p { max-width: 72ch; }

::selection {
  background: var(--color-primary);
  color: #fff;
}

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ===== HEADER ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-divider);
  backdrop-filter: blur(12px);
  background: color-mix(in srgb, var(--color-bg) 85%, transparent);
}

.header-inner {
  max-width: var(--content-wide);
  margin: 0 auto;
  padding: var(--space-3) var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-family: var(--font-display);
  font-weight: 700;
  font-size: var(--text-lg);
  color: var(--color-text);
  flex-shrink: 0;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  overflow-x: auto;
  scrollbar-width: none;
}
.header-nav::-webkit-scrollbar { display: none; }

.filter-pills {
  display: flex;
  gap: var(--space-1);
  flex-shrink: 0;
}

.pill {
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
  color: var(--color-text-muted);
  border: 1px solid transparent;
  transition: all var(--transition-interactive);
  white-space: nowrap;
}

.pill:hover {
  color: var(--color-text);
  background: var(--color-surface-offset);
}

.pill.active {
  color: var(--color-primary);
  background: var(--color-primary-light);
  border-color: var(--color-primary);
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  color: var(--color-text-muted);
  transition: all var(--transition-interactive);
  flex-shrink: 0;
}
.theme-toggle:hover {
  color: var(--color-text);
  background: var(--color-surface-offset);
}

/* ===== HERO ===== */
.hero {
  padding: clamp(var(--space-16), 8vw, var(--space-24)) var(--space-6);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, var(--color-primary) 0%, transparent 70%);
  opacity: 0.04;
  pointer-events: none;
}

.hero-inner {
  max-width: 800px;
  margin: 0 auto;
  position: relative;
}

.hero-eyebrow {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin-bottom: var(--space-4);
}

.hero h1 {
  font-family: var(--font-display);
  font-size: var(--text-3xl);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-4);
  background: linear-gradient(135deg, var(--color-text) 0%, var(--color-text-muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-sub {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  line-height: 1.5;
  margin-bottom: var(--space-8);
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: var(--space-10);
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-num {
  font-family: var(--font-display);
  font-size: var(--text-2xl);
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
}

.stat-label {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: var(--space-1);
}

/* ===== YEAR NAV ===== */
.timeline-section {
  max-width: var(--content-wide);
  margin: 0 auto;
  padding: 0 var(--space-6) var(--space-16);
}

.year-nav {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-8);
  overflow-x: auto;
  scrollbar-width: none;
  padding-bottom: var(--space-2);
  position: sticky;
  top: 58px;
  z-index: 50;
  background: var(--color-bg);
  padding-top: var(--space-4);
}
.year-nav::-webkit-scrollbar { display: none; }

.year-btn {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  transition: all var(--transition-interactive);
  white-space: nowrap;
}

.year-btn:hover {
  color: var(--color-text);
  border-color: var(--color-text-muted);
}

.year-btn.active {
  color: #fff;
  background: var(--color-primary);
  border-color: var(--color-primary);
}

/* ===== TIMELINE ===== */
.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 7px;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--timeline-line);
}

/* Year divider */
.timeline-year-divider {
  position: relative;
  padding: var(--space-6) 0 var(--space-4);
  margin-left: -2rem;
  padding-left: 2rem;
}

.timeline-year-divider .year-label {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 800;
  color: var(--color-text-faint);
  letter-spacing: -0.02em;
}

/* Event card */
.timeline-event {
  position: relative;
  margin-bottom: var(--space-6);
  opacity: 0;
  transform: translateY(16px);
  animation: fadeInUp 0.4s ease forwards;
}

@keyframes fadeInUp {
  to { opacity: 1; transform: translateY(0); }
}

.timeline-event::before {
  content: '';
  position: absolute;
  left: -2rem;
  top: 22px;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 3px solid var(--cat-color, var(--color-primary));
  background: var(--timeline-dot-bg);
  z-index: 2;
  transform: translateX(-0.4375rem);
}

.timeline-event.significance-5::before {
  width: 20px;
  height: 20px;
  border-width: 4px;
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--cat-color, var(--color-primary)) 20%, transparent);
  transform: translateX(-0.5625rem);
}

.event-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  cursor: pointer;
  transition: all var(--transition-interactive);
  position: relative;
  overflow: hidden;
}

.event-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--cat-color, var(--color-primary));
  border-radius: var(--radius-lg) 0 0 var(--radius-lg);
}

.event-card:hover {
  border-color: var(--cat-color, var(--color-primary));
  box-shadow: var(--shadow-md);
  transform: translateX(4px);
}

.event-header {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin-bottom: var(--space-2);
}

.event-icon {
  font-size: 1.5rem;
  flex-shrink: 0;
  line-height: 1;
  margin-top: 2px;
}

.event-meta {
  flex: 1;
  min-width: 0;
}

.event-date {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  margin-bottom: var(--space-1);
}

.event-title {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 2px;
}

.event-org {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
}

.event-badges {
  display: flex;
  gap: var(--space-1);
  flex-shrink: 0;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.event-badge {
  font-size: 0.6875rem;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: var(--radius-full);
  color: var(--cat-color, var(--color-primary));
  background: color-mix(in srgb, var(--cat-color, var(--color-primary)) 12%, transparent);
  white-space: nowrap;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.event-tagline {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-style: italic;
  margin-top: var(--space-1);
}

.event-summary {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-top: var(--space-2);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.event-expand {
  font-size: var(--text-xs);
  color: var(--color-primary);
  margin-top: var(--space-2);
  font-weight: 500;
}

/* ===== MODAL ===== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  backdrop-filter: blur(4px);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-6);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

.modal-overlay.active {
  opacity: 1;
  pointer-events: all;
}

.modal {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  max-width: 640px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  padding: var(--space-8);
  position: relative;
  transform: translateY(16px) scale(0.98);
  transition: transform 0.25s ease;
}

.modal-overlay.active .modal {
  transform: translateY(0) scale(1);
}

.modal-close {
  position: absolute;
  top: var(--space-4);
  right: var(--space-4);
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: var(--color-text-muted);
  transition: all var(--transition-interactive);
}

.modal-close:hover {
  background: var(--color-surface-offset);
  color: var(--color-text);
}

.modal-content .modal-icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-3);
}

.modal-content .modal-date {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  letter-spacing: 0.05em;
  margin-bottom: var(--space-2);
}

.modal-content .modal-title {
  font-family: var(--font-display);
  font-size: var(--text-xl);
  font-weight: 800;
  margin-bottom: var(--space-1);
  line-height: 1.15;
}

.modal-content .modal-org {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  margin-bottom: var(--space-4);
}

.modal-content .modal-tagline {
  font-size: var(--text-lg);
  color: var(--color-text-muted);
  font-style: italic;
  margin-bottom: var(--space-6);
  line-height: 1.4;
}

.modal-content .modal-section {
  margin-bottom: var(--space-5);
}

.modal-content .modal-section-label {
  font-family: var(--font-display);
  font-size: var(--text-sm);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-faint);
  margin-bottom: var(--space-2);
}

.modal-content .modal-section p {
  font-size: var(--text-base);
  line-height: 1.7;
  color: var(--color-text);
}

.modal-content .modal-badge-row {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
  margin-top: var(--space-4);
}

.modal-content .significance-dots {
  display: flex;
  gap: 4px;
  align-items: center;
  margin-top: var(--space-4);
}

.modal-content .significance-dots .dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--color-border);
}

.modal-content .significance-dots .dot.filled {
  background: var(--color-primary);
}

.modal-content .significance-label {
  font-size: var(--text-xs);
  color: var(--color-text-muted);
  margin-left: var(--space-2);
}

/* ===== FOOTER ===== */
footer {
  text-align: center;
  padding: var(--space-8) var(--space-6);
  border-top: 1px solid var(--color-divider);
}

footer a {
  font-size: var(--text-xs);
  color: var(--color-text-faint);
  transition: color var(--transition-interactive);
}

footer a:hover {
  color: var(--color-primary);
}

/* ===== CATEGORY COLORS ===== */
[data-category="llm"] { --cat-color: var(--color-cat-llm); }
[data-category="coding"] { --cat-color: var(--color-cat-coding); }
[data-category="image"] { --cat-color: var(--color-cat-image); }
[data-category="open-source"] { --cat-color: var(--color-cat-open-source); }
[data-category="agents"] { --cat-color: var(--color-cat-agents); }
[data-category="industry"] { --cat-color: var(--color-cat-industry); }

/* ===== EMPTY STATE ===== */
.timeline-empty {
  text-align: center;
  padding: var(--space-16) var(--space-6);
  color: var(--color-text-muted);
}

.timeline-empty p {
  font-size: var(--text-lg);
  margin: 0 auto;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .header-inner {
    flex-direction: column;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
  }

  .header-nav {
    width: 100%;
    justify-content: space-between;
  }

  .filter-pills {
    overflow-x: auto;
    scrollbar-width: none;
    flex: 1;
  }

  .hero {
    padding: var(--space-10) var(--space-4);
  }

  .hero-stats {
    gap: var(--space-6);
  }

  .desktop-only { display: none; }

  .timeline-section {
    padding: 0 var(--space-4) var(--space-12);
  }

  .year-nav {
    top: 100px;
    gap: var(--space-1);
  }

  .event-badges {
    display: none;
  }

  .event-header {
    gap: var(--space-2);
  }

  .modal {
    padding: var(--space-5);
    max-height: 90vh;
  }
}

@media (max-width: 480px) {
  .timeline {
    padding-left: 1.5rem;
  }

  .timeline::before {
    left: 5px;
  }

  .timeline-event::before {
    left: -1.5rem;
    width: 12px;
    height: 12px;
    transform: translateX(-0.3125rem);
  }

  .timeline-event.significance-5::before {
    width: 14px;
    height: 14px;
    transform: translateX(-0.375rem);
  }

  .timeline-year-divider {
    margin-left: -1.5rem;
    padding-left: 1.5rem;
  }

  .event-card {
    padding: var(--space-4);
  }
}