:root {
  color-scheme: light dark;

  /* Colors */
  --color-bg: #fafafa;
  --color-bg-elevated: #ffffff;
  --color-text: #111111;
  --color-text-secondary: #666666;
  --color-text-tertiary: #707070;
  --color-border: #eaeaea;
  --color-accent: #0068cc;
  --color-accent-hover: #005fc0;
  --color-accent-contrast: #ffffff;
  /* Solid accent fills behind white text (buttons, badges) need their own
     value: dark mode's text-safe accent (bright enough at 4.5:1 on black)
     is too light for white-on-fill contrast, so fills use a darker blue. */
  --color-accent-fill: var(--color-accent);
  --color-accent-fill-hover: var(--color-accent-hover);
  --color-nav-bg: rgba(255, 255, 255, 0.72);

  /* Type */
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
  --font-size-hero: clamp(2.5rem, 5vw + 1rem, 4.5rem);
  --font-size-h2: clamp(1.75rem, 3vw + 1rem, 2.75rem);
  --font-size-h3: 1.25rem;
  --font-size-body: 1.0625rem;
  --font-size-small: 0.875rem;
  --letter-spacing-tight: -0.02em;

  /* Spacing scale */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 16px;
  --space-4: 24px;
  --space-5: 40px;
  --space-6: 64px;
  --space-7: 96px;
  --space-8: 140px;

  /* Radii + shadow */
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-pill: 999px;
  --shadow-card: 0 1px 2px rgba(0,0,0,0.04), 0 8px 24px rgba(0,0,0,0.06);
  --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.08);
  --shadow-featured: 0 1px 2px rgba(0, 0, 0, 0.04), 0 12px 32px rgba(0, 104, 204, 0.14);
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #000000;
    --color-bg-elevated: #1c1c1e;
    --color-text: #f5f5f7;
    --color-text-secondary: #a1a1a6;
    --color-text-tertiary: #8e8e93;
    --color-border: #38383a;
    /* Text/icon/border use — verified >=4.5:1 against #000 (5.76:1). */
    --color-accent: #0a84ff;
    --color-accent-hover: #409cff;
    /* Button/badge fills — darker so white text on top clears 4.5:1
       (6.24:1 base, 8.55:1 hover), a separate value from --color-accent
       above since one color can't satisfy both roles in dark mode. */
    --color-accent-fill: #0060b8;
    --color-accent-fill-hover: #004c93;
    --color-nav-bg: rgba(20, 20, 22, 0.72);
    --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.5), 0 8px 24px rgba(0, 0, 0, 0.45);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.5);
    --shadow-featured: 0 1px 2px rgba(0, 0, 0, 0.4), 0 12px 32px rgba(10, 132, 255, 0.22);
  }
}

body {
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  letter-spacing: var(--letter-spacing-tight);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 24px;
  border-radius: var(--radius-pill);
  font-size: var(--font-size-small);
  font-weight: 600;
  text-decoration: none;
  transition: background-color 0.15s ease, border-color 0.15s ease;
  cursor: pointer;
  border: 1px solid transparent;
}
.btn-primary { background: var(--color-accent-fill); color: var(--color-accent-contrast); }
.btn-primary:hover { background: var(--color-accent-fill-hover); }
.btn-ghost { background: transparent; color: var(--color-text); border-color: var(--color-border); }
.btn-ghost:hover { border-color: var(--color-text-tertiary); }
.btn-block { display: flex; width: 100%; }

.card {
  background: var(--color-bg-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-card);
  padding: var(--space-4);
}