/* ============================================================
   base.css — リセット・デザイントークン・タイポグラフィ
   ============================================================ */

:root {
  /* neutral / navy base */
  --c-navy-900: #0f1b30;
  --c-navy-800: #16223b;
  --c-navy-700: #1f2f4d;
  --c-navy-600: #2c4269;
  --c-navy-100: #eef1f7;
  --c-navy-50:  #f6f8fb;

  --c-white: #ffffff;
  --c-ink: #16223b;
  --c-ink-soft: #4a5568;
  --c-border: #dde3ee;
  --c-border-soft: #e9edf5;

  /* accent */
  --c-accent: #d9542f;
  --c-accent-dark: #b8431f;
  --c-accent-soft: #fdece3;

  /* semantic */
  --c-break-bg: #eef0f3;
  --c-break-ink: #8a93a3;
  --c-featured-bg: #fff8ea;
  --c-featured-border: #e8b93a;
  --c-keynote: #6a3fb0;
  --c-sponsor: #1c7a5e;
  --c-pitch: #b8431f;
  --c-media: #1a5fb4;
  --c-original: #2c4269;

  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 14px;

  --shadow-sm: 0 1px 3px rgba(15, 27, 48, 0.08);
  --shadow-md: 0 4px 16px rgba(15, 27, 48, 0.12);
  --shadow-lg: 0 12px 32px rgba(15, 27, 48, 0.18);

  --font-sans: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Hiragino Kaku Gothic ProN",
    "Yu Gothic", "Noto Sans JP", "Segoe UI", Roboto, sans-serif;

  color-scheme: light;
}

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

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

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.65;
  color: var(--c-ink);
  background: var(--c-navy-50);
  min-height: 100dvh;
}

h1, h2, h3, h4, dt, dd { margin: 0; }
p { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
button { font: inherit; color: inherit; }
input { font: inherit; }
a { color: var(--c-accent-dark); }

img { max-width: 100%; display: block; }

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}

/* focus visibility */
a:focus-visible,
button:focus-visible,
input:focus-visible,
[tabindex]:focus-visible {
  outline: 3px solid var(--c-accent);
  outline-offset: 2px;
}

/* ============ internal warning banner ============ */
.internal-banner {
  background: var(--c-accent);
  color: #fff;
  padding: 10px 16px;
  font-size: 13px;
  line-height: 1.5;
  text-align: center;
}
.internal-banner strong {
  display: inline-block;
  background: rgba(0,0,0,0.18);
  padding: 1px 8px;
  border-radius: var(--radius-sm);
  margin-right: 8px;
  font-weight: 700;
}

/* ============ site header ============ */
.site-header {
  background: var(--c-navy-900);
  color: #fff;
  position: sticky;
  top: 0;
  z-index: 40;
  box-shadow: var(--shadow-sm);
}
.site-header__inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 12px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}
.site-header__brand {
  display: flex;
  align-items: baseline;
  gap: 12px;
  flex-wrap: wrap;
}
.site-header__logo {
  font-weight: 800;
  font-size: 18px;
  letter-spacing: 0.02em;
}
.site-header__sub {
  font-size: 12px;
  color: #b7c2da;
}
.site-header__meta {
  display: flex;
  align-items: center;
  gap: 14px;
  font-size: 12px;
  color: #b7c2da;
}

.lang-toggle {
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.25);
  color: #fff;
  padding: 5px 10px;
  border-radius: 999px;
  cursor: pointer;
  font-size: 12px;
  font-weight: 600;
}
.lang-toggle[aria-pressed="true"] .lang-toggle__ja { opacity: 0.45; }
.lang-toggle[aria-pressed="false"] .lang-toggle__en { opacity: 0.45; }

/* ============ intro ============ */
.intro {
  max-width: 900px;
  margin: 0 auto;
  padding: 36px 20px 8px;
}
.intro__title {
  font-size: clamp(22px, 3.4vw, 30px);
  font-weight: 800;
  color: var(--c-navy-900);
  margin-bottom: 14px;
}
.intro__lead {
  font-size: 15px;
  color: var(--c-ink-soft);
  margin-bottom: 10px;
}
.intro__note {
  font-size: 13px;
  color: var(--c-ink-soft);
  background: var(--c-navy-100);
  border-radius: var(--radius-md);
  padding: 10px 14px;
}

/* ============ footer ============ */
.site-footer {
  text-align: center;
  padding: 32px 20px 48px;
  font-size: 12px;
  color: #97a2b8;
}