:root {
  /* Fresh Morning (Light Theme) */
  --bg-color: #F0F9FF;
  --surface-color: #FFFFFF;
  --surface-subtle: #E0F2FE;
  --text-primary: #0F172A;
  --text-secondary: #475569;
  --text-tertiary: #94A3B8;
  --accent: #0EA5E9;
  --accent-hover: #0284C7;
  --accent-container: #BAE6FD;
  --divider: #E2E8F0;
  --border: #CBD5E1;
  --shadow: 0 4px 20px -2px rgba(14, 165, 233, 0.08), 0 2px 6px -1px rgba(0, 0, 0, 0.04);
  --radius-s: 8px;
  --radius-m: 16px;
  --radius-l: 24px;
  --radius-full: 9999px;
  --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --max-width: 1040px;
}

[data-theme="dark"] {
  /* Night DRINKUP (Dark Theme) */
  --bg-color: #0A1118;
  --surface-color: #121E2B;
  --surface-subtle: #1A2B3D;
  --text-primary: #F8FAFC;
  --text-secondary: #94A3B8;
  --text-tertiary: #64748B;
  --accent: #38BDF8;
  --accent-hover: #0EA5E9;
  --accent-container: #0C4A6E;
  --divider: #1E293B;
  --border: #334155;
  --shadow: 0 8px 30px rgba(0, 0, 0, 0.4);
}

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

body {
  font-family: var(--font-family);
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* Header & Nav */
header {
  position: sticky;
  top: 0;
  background-color: var(--bg-color);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--divider);
  z-index: 100;
  padding: 16px 24px;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.brand {
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
  font-weight: 800;
  font-size: 20px;
  letter-spacing: -0.02em;
  color: var(--accent);
}

.brand-icon {
  font-size: 24px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 24px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 15px;
  transition: color 0.2s ease;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
}

.theme-toggle {
  background: var(--surface-subtle);
  border: 1px solid var(--border);
  color: var(--text-primary);
  padding: 6px 12px;
  border-radius: var(--radius-full);
  cursor: pointer;
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s ease;
}

.theme-toggle:hover {
  border-color: var(--accent);
}

/* Main Container */
main {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 40px 24px 80px;
  width: 100%;
}

/* Hero Section */
.hero {
  text-align: center;
  padding: 60px 0 40px;
}

.hero-tag {
  display: inline-block;
  background-color: var(--surface-subtle);
  color: var(--accent);
  padding: 6px 16px;
  border-radius: var(--radius-full);
  font-size: 14px;
  font-weight: 700;
  margin-bottom: 20px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.hero h1 {
  font-size: clamp(36px, 6vw, 64px);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 16px;
}

.hero p {
  font-size: clamp(18px, 2.5vw, 22px);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 32px;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 24px;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background-color: var(--accent);
  color: #FFFFFF;
  text-decoration: none;
  font-weight: 700;
  font-size: 17px;
  padding: 16px 32px;
  border-radius: var(--radius-full);
  box-shadow: 0 4px 14px rgba(14, 165, 233, 0.4);
  transition: transform 0.2s ease, background-color 0.2s ease;
}

.btn-primary:hover {
  background-color: var(--accent-hover);
  transform: translateY(-2px);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background-color: var(--surface-color);
  color: var(--text-primary);
  border: 1px solid var(--border);
  text-decoration: none;
  font-weight: 600;
  font-size: 16px;
  padding: 15px 28px;
  border-radius: var(--radius-full);
  transition: all 0.2s ease;
}

.btn-secondary:hover {
  border-color: var(--accent);
}

.hero-guarantee {
  font-size: 14px;
  color: var(--text-tertiary);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
}

/* Feature Cards Grid */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
  margin-top: 48px;
}

.card {
  background-color: var(--surface-color);
  border: 1px solid var(--divider);
  border-radius: var(--radius-l);
  padding: 32px;
  box-shadow: var(--shadow);
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.card:hover {
  transform: translateY(-4px);
  border-color: var(--accent);
}

.card-icon {
  font-size: 32px;
  margin-bottom: 16px;
  display: inline-block;
}

.card h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
}

.card p {
  color: var(--text-secondary);
  font-size: 15px;
}

/* Download Center Box */
.download-box {
  background: var(--surface-color);
  border: 1px solid var(--border);
  border-radius: var(--radius-l);
  padding: 40px;
  text-align: center;
  max-width: 680px;
  margin: 40px auto 0;
  box-shadow: var(--shadow);
}

.download-box h2 {
  font-size: 28px;
  margin-bottom: 12px;
}

.checksum-badge {
  background-color: var(--surface-subtle);
  padding: 12px 16px;
  border-radius: var(--radius-s);
  font-family: monospace;
  font-size: 13px;
  color: var(--text-secondary);
  word-break: break-all;
  margin: 20px 0;
  border: 1px dashed var(--border);
}

/* Steps List */
.steps-list {
  text-align: left;
  margin: 24px 0;
  padding-left: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  color: var(--text-secondary);
}

/* Footer */
footer {
  border-top: 1px solid var(--divider);
  padding: 40px 24px;
  background-color: var(--surface-color);
  text-align: center;
  color: var(--text-secondary);
  font-size: 14px;
}

.footer-content {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

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

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color 0.2s ease;
}

.footer-links a:hover {
  color: var(--accent);
}

@media (max-width: 640px) {
  .nav-links {
    gap: 12px;
  }
  .hero {
    padding: 30px 0;
  }
}