:root {
  --primary: #20BEFF;
  --primary-dark: #0A9DD6;
  --secondary: #1C1C2E;
  --success: #34C759;
  --warning: #FF9500;
  --error: #FF3B30;

  --bg: #F5F7FA;
  --surface: #FFFFFF;
  --surface-variant: #F0F4F8;
  --on-surface: #1A1A2E;
  --on-surface-variant: #6B7280;
  --divider: #E5E7EB;

  --max-width: 760px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0F0F1A;
    --surface: #1A1A2E;
    --surface-variant: #252538;
    --on-surface: #F0F4F8;
    --on-surface-variant: #9CA3AF;
    --divider: #2D2D44;
  }
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
    Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg);
  color: var(--on-surface);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.page {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 20px 80px;
}

/* Header / brand */
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: inherit;
  margin-bottom: 28px;
}

.brand__icon {
  width: 40px;
  height: 40px;
  flex-shrink: 0;
  border-radius: 10px;
  background: rgba(32, 190, 255, 0.12);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 18px;
  color: var(--primary-dark);
}

.brand__name {
  font-weight: 800;
  font-size: 17px;
  letter-spacing: -0.2px;
}

/* Headings */
h1 {
  font-size: 28px;
  font-weight: 800;
  letter-spacing: -0.5px;
  margin: 0 0 8px;
}

h2 {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.2px;
  margin: 36px 0 10px;
  scroll-margin-top: 16px;
}

.subtitle {
  color: var(--on-surface-variant);
  font-size: 14px;
  margin: 0 0 28px;
}

p, li {
  font-size: 15px;
  color: var(--on-surface);
}

ul {
  padding-left: 22px;
}

li + li {
  margin-top: 6px;
}

a {
  color: var(--primary-dark);
}

strong {
  font-weight: 700;
}

/* Table of contents */
.toc {
  background: var(--surface);
  border: 1px solid var(--divider);
  border-radius: 12px;
  padding: 16px 20px;
  margin-bottom: 8px;
}

.toc__title {
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.8px;
  text-transform: uppercase;
  color: var(--on-surface-variant);
  margin: 0 0 10px;
}

.toc ol {
  margin: 0;
  padding-left: 20px;
  columns: 2;
  -webkit-columns: 2;
  column-gap: 24px;
}

.toc li {
  font-size: 13.5px;
  break-inside: avoid;
  margin-bottom: 4px;
}

.toc a {
  text-decoration: none;
  color: var(--on-surface);
}

.toc a:hover {
  color: var(--primary-dark);
}

/* Cards / callouts */
.card {
  background: var(--surface);
  border: 1px solid var(--divider);
  border-radius: 12px;
  padding: 18px 20px;
  margin: 14px 0;
}

.card--accent {
  border-color: rgba(32, 190, 255, 0.35);
  background: rgba(32, 190, 255, 0.06);
}

.card h3 {
  margin: 0 0 6px;
  font-size: 14px;
  font-weight: 700;
}

.card p:last-child {
  margin-bottom: 0;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 18px;
  border-radius: 10px;
  background: var(--primary);
  color: #fff;
  font-weight: 700;
  font-size: 14px;
  text-decoration: none;
}

.btn--ghost {
  background: transparent;
  border: 1px solid var(--divider);
  color: var(--on-surface);
}

/* Footer */
.footer {
  margin-top: 48px;
  padding-top: 20px;
  border-top: 1px solid var(--divider);
  font-size: 13px;
  color: var(--on-surface-variant);
  display: flex;
  flex-wrap: wrap;
  gap: 8px 16px;
  justify-content: space-between;
  align-items: center;
}

.footer a {
  color: var(--on-surface-variant);
}

.footer__links {
  display: flex;
  gap: 16px;
}

/* Landing page */
.hero {
  text-align: center;
  padding: 48px 0 32px;
}

.hero h1 {
  font-size: 32px;
}

.hero p {
  color: var(--on-surface-variant);
  font-size: 16px;
  max-width: 480px;
  margin: 12px auto 28px;
}

.hero__actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

@media (max-width: 480px) {
  .toc ol {
    columns: 1;
  }
  h1 {
    font-size: 24px;
  }
  .hero h1 {
    font-size: 26px;
  }
}