:root {
  --bg: #f7f7fb;
  --surface: #ffffff;
  --text: #1a1b26;
  --muted: #555a6e;
  --accent: #3d5afe;
  --accent-text: #ffffff;
  --border: #e2e4ee;
  --shadow: 0 6px 24px rgba(20, 24, 50, 0.08);
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12131a;
    --surface: #1c1e28;
    --text: #eceef6;
    --muted: #a7abbe;
    --accent: #8c9eff;
    --accent-text: #12131a;
    --border: #2c2f3d;
    --shadow: 0 6px 24px rgba(0, 0, 0, 0.4);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --bg: #12131a;
  --surface: #1c1e28;
  --text: #eceef6;
  --muted: #a7abbe;
  --accent: #8c9eff;
  --accent-text: #12131a;
  --border: #2c2f3d;
  --shadow: 0 6px 24px rgba(0, 0, 0, 0.4);
  color-scheme: dark;
}

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

html { font-size: 112.5%; } /* 18px base for readability */

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding-inline: max(1rem, env(safe-area-inset-left));
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  line-height: 1.6;
  background: var(--bg);
  color: var(--text);
  transition: background-color 0.25s ease, color 0.25s ease;
}

.site-header, main, .site-footer {
  width: 100%;
  max-width: 60rem;
  margin-inline: auto;
}

.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding-block: 1rem;
}

.brand { font-weight: 700; font-size: 1.1rem; }

.theme-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  min-height: 48px;
  padding: 0.6rem 1.1rem;
  font: inherit;
  font-weight: 600;
  color: var(--accent-text);
  background: var(--accent);
  border: 0;
  border-radius: 999px;
  cursor: pointer;
  transition: transform 0.1s ease, filter 0.2s ease;
}
.theme-toggle:hover { filter: brightness(1.08); }
.theme-toggle:active { transform: scale(0.97); }
.theme-toggle:focus-visible { outline: 3px solid var(--text); outline-offset: 3px; }

main { flex: 1; }

.hero { padding-block: clamp(2rem, 8vw, 5rem) 2rem; }

h1 {
  margin: 0 0 1rem;
  font-size: clamp(2.2rem, 7vw, 3.6rem);
  line-height: 1.15;
  letter-spacing: -0.02em;
}

.lead {
  margin: 0;
  max-width: 38rem;
  font-size: clamp(1.15rem, 2.5vw, 1.4rem);
  color: var(--muted);
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
  gap: 1rem;
  padding-bottom: 3rem;
}

.card {
  padding: 1.5rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 1rem;
  box-shadow: var(--shadow);
}
.card h2 { margin: 0 0 0.4rem; font-size: 1.3rem; color: var(--accent); }
.card p { margin: 0; color: var(--muted); }

.site-footer {
  padding-block: 1.5rem max(1.5rem, env(safe-area-inset-bottom));
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.9rem;
  text-align: center;
}
.site-footer p { margin: 0; }

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}