/* ===== 変数・リセット・文字まわり ===== */
:root {
  --bg: #f4f6f9;
  --bg-accent: radial-gradient(1200px 600px at 12% -8%, #e7ecfd 0%, transparent 60%);
  --surface: #ffffff;
  --surface-2: #f1f3f6;
  --ink: #1b2030;
  --ink-soft: #5c6478;
  --line: #e2e6ee;
  --line-strong: #cdd4e0;
  --accent: #3b5bdb;
  --accent-ink: #ffffff;
  --accent-soft: #e7ecfd;

  --code-bg: #171b26;
  --code-ink: #dfe4f0;

  --radius: 14px;
  --radius-sm: 9px;
  --gap: 20px;
  --shadow-sm: 0 1px 2px rgba(20, 26, 45, 0.06);
  --shadow-md: 0 6px 20px rgba(20, 26, 45, 0.08);
  --shadow-lg: 0 14px 40px rgba(20, 26, 45, 0.12);

  --mono: ui-monospace, "SFMono-Regular", Menlo, Consolas, "Courier New", monospace;
  --sans: system-ui, -apple-system, "Hiragino Sans", "Noto Sans JP", sans-serif;
}

/* OS がダークモードのとき（ただしライト固定が選ばれていなければ） */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #12151d;
    --bg-accent: radial-gradient(1200px 600px at 12% -8%, #1d2740 0%, transparent 60%);
    --surface: #1a1f2b;
    --surface-2: #222836;
    --ink: #e7eaf2;
    --ink-soft: #99a2b8;
    --line: #2c3342;
    --line-strong: #3a4256;
    --accent: #8ba4ff;
    --accent-ink: #12151d;
    --accent-soft: #263156;
    --code-bg: #0e1119;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 6px 20px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 14px 40px rgba(0, 0, 0, 0.45);
  }
}

/* 手動でダークを選んだとき */
:root[data-theme="dark"] {
  --bg: #12151d;
  --bg-accent: radial-gradient(1200px 600px at 12% -8%, #1d2740 0%, transparent 60%);
  --surface: #1a1f2b;
  --surface-2: #222836;
  --ink: #e7eaf2;
  --ink-soft: #99a2b8;
  --line: #2c3342;
  --line-strong: #3a4256;
  --accent: #8ba4ff;
  --accent-ink: #12151d;
  --accent-soft: #263156;
  --code-bg: #0e1119;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 6px 20px rgba(0, 0, 0, 0.35);
  --shadow-lg: 0 14px 40px rgba(0, 0, 0, 0.45);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background-color: var(--bg);
  background-image: var(--bg-accent);
  background-repeat: no-repeat;
  color: var(--ink);
  font-family: var(--sans);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 {
  line-height: 1.35;
  letter-spacing: 0.01em;
}

code { font-family: var(--mono); }

a { color: var(--accent); }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip-link {
  position: absolute;
  left: -999px;
}
.skip-link:focus {
  left: 12px; top: 12px;
  z-index: 10;
  background: var(--surface);
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  box-shadow: var(--shadow-md);
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

/* 動きを減らす設定の人には、アニメーションを出さない */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}