/* ============================================
   GDG HCMC 13th Birthday — Stylesheet
   Google Brand Colors + Dark Theme
   ============================================ */

/* --- CSS Variables / Design Tokens --- */
:root {
  --g-blue: #4285F4;
  --g-red: #EA4335;
  --g-yellow: #FBBC04;
  --g-green: #34A853;
  --bg-dark: #0a0a1a;
  --bg-card: rgba(20, 20, 40, 0.9);
  --bg-glass: rgba(255, 255, 255, 0.06);
  --border-glass: rgba(255, 255, 255, 0.1);
  --text-primary: #ffffff;
  --text-secondary: rgba(255, 255, 255, 0.7);
  --text-muted: rgba(255, 255, 255, 0.45);
  --font-main: 'Inter', 'Google Sans', system-ui, -apple-system, sans-serif;
  --font-display: 'Space Grotesk', 'Inter', sans-serif;
  --section-height: 100vh;
  --timeline-line-color: rgba(255, 255, 255, 0.12);
}

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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-main);
  background: var(--bg-dark);
  color: var(--text-primary);
  overflow-x: hidden;
  line-height: 1.6;
}

/* --- Language Toggle --- */
body.lang-vi .lang-en { display: none !important; }
body.lang-en .lang-vi { display: none !important; }

/* --- Three.js Canvas --- */
#scene-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 0;
  pointer-events: none;
  background: transparent !important;
}

/* --- Background Image Crossfade Layers --- */
.bg-layer {
  position: fixed;
  inset: 0;
  z-index: -1;
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  opacity: 0;
  transition: opacity 1.5s ease-in-out;
  filter: brightness(0.4); /* Removed blur(3px) for massive scroll performance gain */
  transform: translateZ(0);
}

.bg-layer.active {
  opacity: 1;
}

/* --- Loading Screen --- */
#loading-screen {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--bg-dark);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.8s ease, visibility 0.8s ease;
}

#loading-screen.hidden {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.loader-content { text-align: center; }

.loader-dots {
  display: flex;
  gap: 8px;
  justify-content: center;
  margin-bottom: 20px;
}

.loader-dots span {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  animation: loaderBounce 1.2s infinite ease-in-out;
}

.loader-dots span:nth-child(2) { animation-delay: 0.1s; }
.loader-dots span:nth-child(3) { animation-delay: 0.2s; }
.loader-dots span:nth-child(4) { animation-delay: 0.3s; }

@keyframes loaderBounce {
  0%, 80%, 100% { transform: scale(0.6); opacity: 0.4; }
  40% { transform: scale(1.2); opacity: 1; }
}

.loader-content p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  letter-spacing: 0.05em;
}

/* --- Language Toggle Button --- */
#lang-toggle {
  position: fixed;
  top: 24px;
  right: 24px;
  z-index: 100;
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-glass);
  color: var(--text-primary);
  padding: 8px 16px;
  border-radius: 20px;
  cursor: pointer;
  font-family: var(--font-main);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  transition: all 0.3s ease;
}

#lang-toggle:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: scale(1.05);
}

/* --- Year Progress Indicator --- */
#year-indicator {
  position: fixed;
  left: 24px;
  top: 50%;
  transform: translateY(-50%);
  z-index: 100;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  opacity: 0;
  transition: opacity 0.5s ease;
}

#year-indicator.visible { opacity: 1; }

#year-text {
  font-family: var(--font-display);
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--g-blue);
  text-shadow: 0 0 20px rgba(66, 133, 244, 0.5);
}

#progress-bar {
  width: 3px;
  height: 120px;
  background: var(--timeline-line-color);
  border-radius: 2px;
  overflow: hidden;
}

#progress-fill {
  width: 100%;
  height: 0%;
  background: linear-gradient(to bottom, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green));
  border-radius: 2px;
  transition: height 0.15s ease;
}

/* --- Scroll Container --- */
#scroll-container {
  position: relative;
  z-index: 1;
}

.section {
  min-height: var(--section-height);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
  position: relative;
}

/* --- Hero Section --- */
#hero {
  min-height: 100vh;
  text-align: center;
  flex-direction: column;
}

.hero-content {
  max-width: 700px;
  animation: heroFadeIn 1.5s ease-out 0.5s both;
}

@keyframes heroFadeIn {
  from { opacity: 0; transform: translateY(40px); }
  to { opacity: 1; transform: translateY(0); }
}

.hero-badge {
  display: inline-block;
  background: var(--bg-glass);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-glass);
  padding: 6px 20px;
  border-radius: 30px;
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.hero-title {
  font-family: var(--font-display);
  font-size: clamp(3.5rem, 12vw, 8rem);
  font-weight: 800;
  line-height: 0.95;
  margin-bottom: 20px;
}

.hero-gdg {
  display: block;
  background: linear-gradient(135deg, var(--g-blue), var(--g-green));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-hcmc {
  display: block;
  background: linear-gradient(135deg, var(--g-red), var(--g-yellow));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-years {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin: 30px 0 20px;
}

.hero-number {
  font-family: var(--font-display);
  font-size: clamp(4rem, 15vw, 9rem);
  font-weight: 900;
  background: linear-gradient(135deg, var(--g-blue) 0%, var(--g-red) 33%, var(--g-yellow) 66%, var(--g-green) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  filter: drop-shadow(0 0 30px rgba(66, 133, 244, 0.3));
}

.hero-label {
  text-align: left;
  font-size: clamp(0.9rem, 2.5vw, 1.3rem);
  font-weight: 700;
  letter-spacing: 0.15em;
  color: var(--text-secondary);
  line-height: 1.3;
}

.hero-subtitle {
  font-size: clamp(0.9rem, 2vw, 1.1rem);
  color: var(--text-muted);
  margin-bottom: 50px;
}

.scroll-indicator {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 10px;
  font-size: 0.8rem;
  color: var(--text-muted);
  letter-spacing: 0.1em;
  animation: scrollPulse 2s ease-in-out infinite;
}

@keyframes scrollPulse {
  0%, 100% { opacity: 0.5; transform: translateY(0); }
  50% { opacity: 1; transform: translateY(8px); }
}

.scroll-arrow {
  width: 40px;
  height: 40px;
  border: 1px solid var(--border-glass);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--g-blue);
}

/* --- Timeline --- */
#timeline-container {
  position: relative;
  padding: 0 20px;
}

/* Timeline vertical line */
#timeline-container::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 2px;
  background: linear-gradient(
    to bottom,
    transparent,
    var(--g-blue) 5%,
    var(--g-red) 30%,
    var(--g-yellow) 60%,
    var(--g-green) 90%,
    transparent
  );
  opacity: 0.25;
  transform: translateX(-50%);
}

/* Event Section */
.event-section {
  min-height: 80vh;
  display: flex;
  align-items: center;
  padding: 60px 0;
  position: relative;
}

/* Timeline dot — REMOVED per user feedback */
.event-section::before {
  display: none;
}

.event-section.in-view::before {
  display: none;
}

/* Event card layout */
.event-inner {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 60px;
}

.event-section:nth-child(odd) .event-inner {
  flex-direction: row;
}

.event-section:nth-child(even) .event-inner {
  flex-direction: row-reverse;
}

.event-year-side {
  flex: 1;
  text-align: center;
}

.event-year-big {
  font-family: var(--font-display);
  font-size: clamp(3rem, 8vw, 6rem);
  font-weight: 900;
  opacity: 0.15;
  line-height: 1;
  transition: opacity 0.5s ease;
}

.event-section.in-view .event-year-big {
  opacity: 0.35;
}

.event-card-side {
  flex: 1.2;
}

/* Glassmorphism Event Card */
.event-card {
  background: var(--bg-card);
  border: 1px solid var(--border-glass);
  border-radius: 20px;
  padding: 32px;
  position: relative;
  overflow: hidden;
  transform: translateY(40px) translateZ(0);
  opacity: 0;
  transition: transform 0.7s cubic-bezier(0.16, 1, 0.3, 1),
              opacity 0.7s ease,
              border-color 0.3s ease;
}

.event-section.in-view .event-card {
  transform: translateY(0);
  opacity: 1;
}

.event-card:hover {
  border-color: rgba(255, 255, 255, 0.2);
}

/* Color accent stripe */
.event-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--accent);
  border-radius: 20px 20px 0 0;
}

.event-card .event-date {
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  margin-bottom: 8px;
  opacity: 0.7;
}

.event-card .event-title {
  font-family: var(--font-display);
  font-size: clamp(1.4rem, 4vw, 2rem);
  font-weight: 700;
  margin-bottom: 16px;
  line-height: 1.3;
}

.event-card .event-desc {
  font-size: 1.1rem;
  color: var(--text-primary);
  opacity: 0.9;
  line-height: 1.8;
  font-style: italic;
}

/* Event Image */
.event-image-wrapper {
  margin-top: 20px;
  border-radius: 12px;
  overflow: hidden;
  border: 1px solid var(--border-glass);
}

.event-image-wrapper img {
  width: 100%;
  height: 200px;
  object-fit: cover;
  display: block;
  transition: transform 0.5s ease;
}

.event-card:hover .event-image-wrapper img {
  transform: scale(1.05);
}

/* Birthday special card */
.event-card.birthday-card {
  background: linear-gradient(135deg,
    rgba(66, 133, 244, 0.15),
    rgba(234, 67, 53, 0.1),
    rgba(251, 188, 4, 0.1),
    rgba(52, 168, 83, 0.15)
  );
  border-color: rgba(66, 133, 244, 0.3);
}

.event-card.birthday-card::before {
  height: 4px;
  background: linear-gradient(90deg, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green)) !important;
}

.event-card.birthday-card .event-title {
  background: linear-gradient(90deg, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
  display: inline-block;
}

/* --- GDG Logo --- */
#gdg-logo {
  position: fixed;
  top: 30px;
  left: 40px;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 700;
  color: #fff;
  opacity: 0.9;
  letter-spacing: -0.02em;
  pointer-events: none;
}

#gdg-logo .logo-icon {
  font-size: 1.4rem;
  font-weight: 900;
  color: var(--g-blue);
  background: linear-gradient(90deg, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

/* --- Finale Section --- */
#finale {
  min-height: 100vh;
  text-align: center;
  flex-direction: column;
  padding: 80px 20px;
}

.finale-content {
  max-width: 600px;
}

.finale-emoji {
  font-size: 5rem;
  margin-bottom: 20px;
  animation: cakeBounce 2s ease-in-out infinite;
}

@keyframes cakeBounce {
  0%, 100% { transform: scale(1) rotate(0deg); }
  25% { transform: scale(1.1) rotate(-5deg); }
  75% { transform: scale(1.1) rotate(5deg); }
}

.finale-title {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 5vw, 2.8rem);
  font-weight: 800;
  margin-bottom: 16px;
  background: linear-gradient(135deg, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.finale-subtitle {
  font-size: 1.05rem;
  color: var(--text-secondary);
  margin-bottom: 40px;
  line-height: 1.7;
}

.finale-event-card {
  background: var(--bg-card);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border: 1px solid rgba(66, 133, 244, 0.3);
  border-radius: 20px;
  padding: 32px;
  text-align: left;
  margin-bottom: 30px;
  position: relative;
  overflow: hidden;
}

.finale-event-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--g-blue), var(--g-red), var(--g-yellow), var(--g-green));
}

.event-badge-live {
  display: inline-block;
  background: rgba(234, 67, 53, 0.15);
  color: var(--g-red);
  padding: 4px 12px;
  border-radius: 12px;
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  margin-bottom: 12px;
  animation: livePulse 2s infinite;
}

@keyframes livePulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.6; }
}

.finale-event-card h3 {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 16px;
}

.event-details {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 24px;
}

.detail-item {
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.cta-button {
  display: inline-block;
  background: linear-gradient(135deg, var(--g-blue), #5a9cf5);
  color: white;
  text-decoration: none;
  padding: 14px 32px;
  border-radius: 30px;
  font-weight: 600;
  font-size: 1rem;
  transition: all 0.3s ease;
  box-shadow: 0 4px 20px rgba(66, 133, 244, 0.4);
}

.cta-button:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(66, 133, 244, 0.5);
}

.finale-hashtags {
  font-size: 0.8rem;
  color: var(--g-blue);
  opacity: 0.6;
  letter-spacing: 0.02em;
  margin-bottom: 60px;
  word-spacing: 8px;
}

/* --- Footer --- */
.site-footer {
  text-align: center;
  padding-top: 40px;
  border-top: 1px solid var(--border-glass);
}

.site-footer p {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.footer-links {
  display: flex;
  gap: 20px;
  justify-content: center;
}

.footer-links a {
  color: var(--g-blue);
  text-decoration: none;
  font-size: 0.85rem;
  transition: opacity 0.3s;
}

.footer-links a:hover { opacity: 0.7; }

/* --- Confetti Canvas --- */
#confetti-canvas {
  position: fixed;
  inset: 0;
  z-index: 200;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.5s ease;
}

#confetti-canvas.active { opacity: 1; }

/* --- Responsive --- */
@media (max-width: 768px) {
  #year-indicator { display: none; }

  #lang-toggle {
    top: 12px;
    right: 12px;
    padding: 6px 12px;
    font-size: 0.7rem;
  }

  .event-inner {
    flex-direction: column !important;
    gap: 20px;
    padding: 0 10px;
  }

  .event-year-side {
    order: -1;
  }

  .event-year-big {
    font-size: 2.5rem !important;
  }

  .event-card {
    padding: 24px;
  }

  #timeline-container::before {
    left: 20px;
  }



  .event-section {
    min-height: auto;
    padding: 40px 0;
  }

  .hero-title {
    font-size: clamp(2.5rem, 15vw, 5rem);
  }

  .hero-number {
    font-size: clamp(3rem, 18vw, 6rem);
  }

  .finale-event-card {
    padding: 24px;
  }
}

@media (max-width: 480px) {
  .hero-years {
    flex-direction: column;
    gap: 8px;
  }

  .hero-label {
    text-align: center;
  }
}

/* --- Utility: No image placeholder --- */
.no-image-placeholder {
  width: 100%;
  height: 120px;
  margin-top: 20px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
  opacity: 0.3;
}