/* Concept 3: The Time Machine
   Honor 25+ years of web presence with era-based navigation */

:root {
  /* Default (2020s) */
  --color-bg: #0D1117;
  --color-text: #C9D1D9;
  --color-text-muted: #6E7681;
  --color-accent: #58A6FF;
  --color-card-bg: #161B22;
  --color-border: rgba(201, 209, 217, 0.1);
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --grain-opacity: 0;
  --transition-speed: 0.6s;
}

/* Era: 2020s - Modern dark */
.era-2020s {
  --color-bg: #0D1117;
  --color-text: #C9D1D9;
  --color-text-muted: #6E7681;
  --color-accent: #58A6FF;
  --color-card-bg: #161B22;
  --color-border: rgba(201, 209, 217, 0.1);
  --grain-opacity: 0;
}

/* Era: 2010s - Flat, minimal */
.era-2010s {
  --color-bg: #FAFAFA;
  --color-text: #333333;
  --color-text-muted: #888888;
  --color-accent: #1DA1F2;
  --color-card-bg: #FFFFFF;
  --color-border: rgba(0, 0, 0, 0.08);
  --grain-opacity: 0;
}

/* Era: 2000s - Warm, textured (brico) */
.era-2000s {
  --color-bg: #E9C5A9;
  --color-text: #3D3024;
  --color-text-muted: #7A6B5A;
  --color-accent: #B85A3C;
  --color-card-bg: rgba(255, 255, 255, 0.7);
  --color-border: rgba(61, 48, 36, 0.15);
  --grain-opacity: 0.04;
}

/* Era: 1999 - GeoCities vibes */
.era-1999 {
  --color-bg: #000080;
  --color-text: #FFFF00;
  --color-text-muted: #00FFFF;
  --color-accent: #FF00FF;
  --color-card-bg: #000000;
  --color-border: #FFFF00;
  --grain-opacity: 0.08;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  transition: background var(--transition-speed), color var(--transition-speed);
}

/* Film grain overlay */
.grain-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
  opacity: var(--grain-opacity);
  pointer-events: none;
  z-index: 100;
  transition: opacity var(--transition-speed);
}

.container {
  max-width: 700px;
  margin: 0 auto;
  padding: 60px 24px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.header {
  text-align: center;
  margin-bottom: 50px;
}

.header h1 {
  font-size: 2.5rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  margin-bottom: 8px;
  transition: color var(--transition-speed);
}

.tagline {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  transition: color var(--transition-speed);
}

/* 1999 special header styling */
.era-1999 .header h1 {
  font-family: "Comic Sans MS", "Comic Sans", cursive, sans-serif;
  text-shadow: 2px 2px #FF00FF;
}

.era-1999 .tagline {
  animation: blink1999 1s step-end infinite;
}

@keyframes blink1999 {
  50% { opacity: 0; }
}

/* Timeline */
.timeline {
  margin-bottom: 40px;
  text-align: center;
}

.timeline-track {
  display: inline-flex;
  gap: 8px;
  padding: 8px;
  background: var(--color-card-bg);
  border-radius: 30px;
  border: 1px solid var(--color-border);
  transition: background var(--transition-speed), border-color var(--transition-speed);
}

.era-btn {
  padding: 10px 20px;
  border: none;
  background: transparent;
  color: var(--color-text-muted);
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: 20px;
  cursor: pointer;
  transition: all 0.3s;
}

.era-btn:hover {
  color: var(--color-text);
}

.era-btn.active {
  background: var(--color-accent);
  color: #FFFFFF;
}

.era-1999 .era-btn.active {
  color: #000000;
}

.timeline-indicator {
  margin-top: 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  opacity: 0.7;
}

.indicator-text {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--color-text-muted);
}

.indicator-arrow {
  font-size: 0.8rem;
  color: var(--color-accent);
  animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(4px); }
}

/* Era content panels */
.era-content {
  flex: 1;
}

.era-panel {
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 32px;
  transition: background var(--transition-speed), border-color var(--transition-speed), opacity 0.3s, transform 0.3s;
}

.era-panel.hidden {
  display: none;
}

.era-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 16px;
  flex-wrap: wrap;
  gap: 8px;
}

.era-header h2 {
  font-size: 1.5rem;
  font-weight: 600;
  transition: color var(--transition-speed);
}

.era-years {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  font-weight: 500;
}

.era-desc {
  font-size: 1rem;
  line-height: 1.7;
  color: var(--color-text-muted);
  margin-bottom: 24px;
  transition: color var(--transition-speed);
}

/* Era links */
.era-links {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.era-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  color: var(--color-text);
  text-decoration: none;
  font-size: 0.9rem;
  transition: all 0.2s;
}

.era-link:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: var(--color-accent);
  transform: translateY(-2px);
}

.era-2010s .era-link,
.era-2000s .era-link {
  background: rgba(0, 0, 0, 0.03);
}

.era-2010s .era-link:hover,
.era-2000s .era-link:hover {
  background: rgba(0, 0, 0, 0.06);
}

.era-1999 .era-link {
  border: 2px solid var(--color-accent);
  background: transparent;
}

.era-1999 .era-link:hover {
  background: var(--color-accent);
  color: #000000;
}

.link-icon {
  font-size: 1.1rem;
}

/* 1999 special styling */
.era-1999 .era-panel {
  border: 3px solid #FFFF00;
  border-radius: 0;
}

.era-1999 .era-header h2 {
  font-family: "Comic Sans MS", "Comic Sans", cursive, sans-serif;
}

/* Footer */
.footer {
  margin-top: 50px;
  text-align: center;
}

.footer a {
  color: var(--color-accent);
  text-decoration: none;
  font-size: 0.9rem;
}

.footer a:hover {
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 600px) {
  .container {
    padding: 40px 16px;
  }

  .header h1 {
    font-size: 2rem;
  }

  .timeline-track {
    flex-wrap: wrap;
    justify-content: center;
  }

  .era-btn {
    padding: 8px 16px;
    font-size: 0.85rem;
  }

  .era-panel {
    padding: 24px;
  }

  .era-header {
    flex-direction: column;
    gap: 4px;
  }
}