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

:root {
  --bg: #0f172a;
  --surface: #1e293b;
  --border: #334155;
  --text: #f8fafc;
  --text-muted: #94a3b8;
  --primary: #6366f1;
  --primary-light: #818cf8;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
}

/* ── Top bar ── */
.top-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 200;
  padding: 0.55rem 1.25rem;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(51, 65, 85, 0.6);
}

.back-link {
  font-size: 0.78rem;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s;
}
.back-link:hover { color: var(--text); }

/* ══════════════════════════════════════
   INTRO SCREEN
══════════════════════════════════════ */
.intro-screen {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 5rem 1rem 2rem;
}

.intro-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 1.5rem;
  padding: 2.5rem 2rem;
  max-width: 440px;
  width: 100%;
  text-align: center;
  box-shadow: 0 24px 60px rgba(0, 0, 0, 0.5);
  animation: fadeUp 0.5s ease;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(24px); }
  to   { opacity: 1; transform: translateY(0); }
}

.intro-icon { font-size: 3.5rem; margin-bottom: 1rem; }

.intro-title {
  font-size: 1.75rem;
  font-weight: 800;
  background: linear-gradient(135deg, #f8fafc 0%, var(--primary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.75rem;
}

.intro-desc {
  font-size: 0.93rem;
  color: var(--text-muted);
  line-height: 1.65;
  margin-bottom: 1.75rem;
}

.date-input-wrapper { margin-bottom: 1.25rem; text-align: left; }

.date-label {
  display: block;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  margin-bottom: 0.5rem;
}

.date-selects {
  display: grid;
  grid-template-columns: 2fr 1fr 1.5fr;
  gap: 0.5rem;
}

.date-select {
  width: 100%;
  padding: 0.72rem 2rem 0.72rem 0.85rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  color: var(--text);
  font-size: 0.92rem;
  font-family: inherit;
  outline: none;
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='8' viewBox='0 0 12 8'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%2394a3b8' stroke-width='1.5' fill='none' stroke-linecap='round'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.75rem center;
  transition: border-color 0.2s;
}
.date-select:focus {
  border-color: var(--primary-light);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.18);
}
.date-select option { background: #1e293b; color: var(--text); }

.start-btn {
  width: 100%;
  padding: 0.875rem;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  border: none;
  border-radius: 0.75rem;
  color: white;
  font-size: 1rem;
  font-weight: 700;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s;
  margin-bottom: 1rem;
}
.start-btn:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.4);
}
.start-btn:disabled { opacity: 0.4; cursor: not-allowed; }

.privacy-note { font-size: 0.72rem; color: var(--text-muted); opacity: 0.65; }

/* ══════════════════════════════════════
   STATS SCREEN
══════════════════════════════════════ */
.stats-screen { /* natural flow */ }

/* Sticky bar */
.sticky-bar {
  position: fixed;
  top: 34px; /* below top-bar */
  left: 0;
  right: 0;
  z-index: 190;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.45rem 1.25rem;
  background: rgba(15, 23, 42, 0.75);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(51, 65, 85, 0.4);
  font-size: 0.8rem;
  color: var(--text-muted);
}

.sticky-change {
  background: none;
  border: 1px solid var(--border);
  border-radius: 0.375rem;
  color: var(--text-muted);
  font-size: 0.75rem;
  font-family: inherit;
  padding: 0.25rem 0.65rem;
  cursor: pointer;
  transition: all 0.15s;
}
.sticky-change:hover { color: var(--text); border-color: var(--primary-light); }

/* ── Slides ── */
.stat-slide {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--slide-bg, var(--bg));
  transition: background 0.6s ease;
  padding: 6rem 1.5rem 3rem;
}

.slide-inner {
  text-align: center;
  max-width: 540px;
  width: 100%;
}

/* ── Hero slide ── */
.slide-hero {
  background: var(--bg);
  --slide-bg: #0f172a;
}

.slide-since {
  font-size: 1rem;
  color: var(--text-muted);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-weight: 600;
  margin-bottom: 1rem;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.6s ease 0.1s, transform 0.6s ease 0.1s;
}

.hero-age {
  font-size: clamp(3rem, 12vw, 6rem);
  font-weight: 800;
  line-height: 1.05;
  background: linear-gradient(135deg, #f8fafc 0%, var(--primary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 0.5rem;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease 0.2s, transform 0.6s ease 0.2s;
}

.hero-age-sub {
  font-size: clamp(1rem, 3vw, 1.4rem);
  color: var(--text-muted);
  margin-bottom: 2.5rem;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.6s ease 0.3s, transform 0.6s ease 0.3s;
}

.scroll-hint {
  font-size: 0.85rem;
  color: var(--text-muted);
  opacity: 0;
  animation: none;
  transition: opacity 0.6s ease 0.5s;
}

.slide-hero.slide-visible .slide-since,
.slide-hero.slide-visible .hero-age,
.slide-hero.slide-visible .hero-age-sub {
  opacity: 1;
  transform: translateY(0);
}
.slide-hero.slide-visible .scroll-hint {
  opacity: 1;
  animation: bounce 2s ease-in-out 1s infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(6px); }
}

/* ── Stat slides ── */
.slide-emoji {
  font-size: clamp(3rem, 8vw, 5rem);
  line-height: 1;
  margin-bottom: 1.25rem;
  opacity: 0;
  transform: scale(0.7);
  transition: opacity 0.5s ease, transform 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.slide-number {
  font-size: clamp(2.5rem, 10vw, 6rem);
  font-weight: 900;
  line-height: 1;
  color: var(--slide-color, var(--primary-light));
  font-variant-numeric: tabular-nums;
  margin-bottom: 0.75rem;
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.5s ease 0.1s, transform 0.5s ease 0.1s;
  word-break: break-word;
}

.slide-label {
  font-size: clamp(1.1rem, 3.5vw, 1.75rem);
  font-weight: 700;
  color: var(--text);
  margin-bottom: 0.75rem;
  opacity: 0;
  transform: translateY(16px);
  transition: opacity 0.5s ease 0.2s, transform 0.5s ease 0.2s;
}

.slide-desc {
  font-size: clamp(0.85rem, 2vw, 1rem);
  color: var(--text-muted);
  line-height: 1.6;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease 0.3s, transform 0.5s ease 0.3s;
}

/* ── Start-age note ── */
.slide-start-age {
  display: inline-block;
  font-size: 0.68rem;
  color: var(--text-muted);
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 999px;
  padding: 0.18rem 0.65rem;
  margin-top: 0.5rem;
  opacity: 0;
  transition: opacity 0.5s ease 0.25s;
}
.stat-slide.slide-visible .slide-start-age { opacity: 1; }

/* ── Sub-stats row ── */
.slide-substats {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  margin: 1rem 0 0.25rem;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease 0.35s, transform 0.5s ease 0.35s;
}

.substat {
  display: flex;
  flex-direction: column;
  align-items: center;
  background: rgba(255,255,255,0.05);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 0.75rem;
  padding: 0.5rem 1rem;
  min-width: 100px;
}

.substat-value {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--slide-color, var(--primary-light));
  font-variant-numeric: tabular-nums;
}

.substat-label {
  font-size: 0.68rem;
  color: var(--text-muted);
  margin-top: 0.15rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ── Analogy block ── */
.slide-analogy {
  margin-top: 1.25rem;
  padding: 0.9rem 1.1rem;
  background: rgba(255,255,255,0.05);
  border-left: 3px solid var(--slide-color, var(--primary-light));
  border-radius: 0 0.625rem 0.625rem 0;
  font-size: clamp(0.82rem, 1.8vw, 0.95rem);
  color: var(--text-muted);
  line-height: 1.65;
  text-align: left;
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.5s ease 0.4s, transform 0.5s ease 0.4s;
}

.slide-analogy strong {
  color: var(--text);
  font-weight: 700;
}

/* ── Fact pill ── */
.slide-fact {
  margin-top: 1rem;
  font-size: clamp(0.78rem, 1.6vw, 0.875rem);
  color: var(--text-muted);
  line-height: 1.55;
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.5s ease 0.5s, transform 0.5s ease 0.5s;
}

.fact-pill {
  display: inline-block;
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.12);
  border-radius: 999px;
  padding: 0.15rem 0.55rem;
  margin-right: 0.4rem;
  color: var(--slide-color, var(--primary-light));
  vertical-align: middle;
}

/* Trigger animations when slide enters viewport */
.stat-slide.slide-visible .slide-emoji {
  opacity: 1;
  transform: scale(1);
}
.stat-slide.slide-visible .slide-number,
.stat-slide.slide-visible .slide-label,
.stat-slide.slide-visible .slide-desc {
  opacity: 1;
  transform: translateY(0);
}
.stat-slide.slide-visible .slide-substats,
.stat-slide.slide-visible .slide-analogy,
.stat-slide.slide-visible .slide-fact {
  opacity: 1;
  transform: translateY(0);
}

/* ── Final slide ── */
.slide-final {
  background: #0a0f1e;
  --slide-bg: #0a0f1e;
}

.final-icon {
  font-size: 4rem;
  margin-bottom: 1.25rem;
  animation: spin 3s ease-in-out infinite;
}
@keyframes spin {
  0%, 100% { transform: rotate(-5deg) scale(1); }
  50%       { transform: rotate(5deg) scale(1.1); }
}

.final-title {
  font-size: clamp(1.5rem, 5vw, 2.5rem);
  font-weight: 800;
  background: linear-gradient(135deg, #f8fafc 0%, var(--primary-light) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 1rem;
  line-height: 1.2;
}

.final-sub {
  font-size: 1rem;
  color: var(--text-muted);
  line-height: 1.65;
  margin-bottom: 2rem;
}

.final-change-btn {
  display: inline-block;
  padding: 0.8rem 2rem;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  border: none;
  border-radius: 0.75rem;
  color: white;
  font-size: 1rem;
  font-weight: 700;
  font-family: inherit;
  cursor: pointer;
  transition: all 0.2s;
}
.final-change-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(99, 102, 241, 0.4);
}

/* ── Responsive ── */
@media (max-width: 500px) {
  .date-selects { grid-template-columns: 1fr 1fr; }
  .date-selects #sel-year { grid-column: 1 / -1; }
}