:root {
  color-scheme: dark;
  --bg: #071015;
  --fg: #eef7f8;
  --muted: #8fa2ae;
  --accent: #78f6cf;
  --card: #0b171e;
  --border: rgba(169, 201, 214, 0.16);
  --border-strong: rgba(169, 201, 214, 0.28);
  --canvas-deep: #040a0e;
  --surface-raised: #10212a;
  --faint: #708690;
  --blue: #5aa9ff;
  --page-width: 1480px;
  --page-x: clamp(24px, 5vw, 76px);
  --font: Inter, "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Yu Gothic",
    system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
}

html {
  scroll-behavior: smooth;
}

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

body.app-page {
  min-width: 320px;
  min-height: 100vh;
  background:
    radial-gradient(circle at 78% 16%, rgba(90, 169, 255, 0.12), transparent 24%),
    radial-gradient(circle at 54% 54%, rgba(120, 246, 207, 0.055), transparent 30%),
    linear-gradient(145deg, var(--canvas-deep), var(--bg) 48%, #08131a);
  color: var(--fg);
  font-family: var(--font);
  -webkit-font-smoothing: antialiased;
}

body.app-page::before {
  position: fixed;
  z-index: -1;
  inset: 0;
  background-image:
    linear-gradient(rgba(153, 190, 203, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(153, 190, 203, 0.035) 1px, transparent 1px);
  background-size: 54px 54px;
  content: "";
  pointer-events: none;
  mask-image: linear-gradient(to bottom, #000, rgba(0, 0, 0, 0.45) 72%, transparent);
}

body.app-page ::selection {
  background: rgba(120, 246, 207, 0.24);
  color: var(--fg);
}

.app-site-header {
  position: sticky;
  z-index: 1000;
  top: 0;
  flex: 0 0 auto;
  padding: 0;
  border-bottom: 1px solid var(--border);
  background: rgba(5, 12, 17, 0.86);
  backdrop-filter: blur(18px) saturate(140%);
}

.app-site-header__inner {
  display: flex;
  width: min(100%, var(--page-width));
  min-height: 82px;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  margin-inline: auto;
  padding-inline: var(--page-x);
}

.app-brand {
  display: inline-flex;
  align-items: center;
  gap: 13px;
  width: max-content;
  color: var(--fg);
  font-size: 14px;
  font-weight: 650;
  letter-spacing: 0.03em;
  text-decoration: none;
}

.app-brand-mark {
  display: grid;
  width: 34px;
  height: 34px;
  flex: 0 0 auto;
  place-items: center;
  border: 1px solid rgba(120, 246, 207, 0.56);
  border-radius: 50%;
  box-shadow: 0 0 28px rgba(120, 246, 207, 0.1);
  color: var(--accent);
  font-size: 10px;
  font-weight: 700;
}

.app-brand small {
  margin-left: 5px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 450;
}

.app-site-header .back-link {
  display: inline-flex;
  min-height: 44px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin: 0;
  padding: 9px 15px;
  border: 1px solid var(--border-strong);
  border-radius: 0;
  background: transparent;
  color: var(--fg);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.035em;
  line-height: 1.4;
  text-decoration: none;
  transition:
    border-color 180ms ease,
    background-color 180ms ease,
    color 180ms ease,
    transform 180ms ease;
}

.app-site-header .back-link:hover,
.app-site-header .back-link:focus-visible {
  border-color: var(--accent);
  background: rgba(120, 246, 207, 0.08);
  color: var(--accent);
  text-decoration: none;
  transform: translateY(-2px);
}

.app-main {
  width: min(var(--maxw, 1100px), calc(100% - (var(--page-x) * 2)));
  max-width: none;
  margin-inline: auto;
  padding: 58px 0 80px;
}

.app-intro {
  margin-bottom: 36px;
  padding-bottom: 30px;
  border-bottom: 1px solid var(--border-strong);
}

.app-kicker {
  margin: 0 0 14px;
  color: var(--accent);
  font-size: 10px;
  font-weight: 650;
  letter-spacing: 0.18em;
  line-height: 1;
  text-transform: uppercase;
}

.app-intro h1 {
  margin: 0;
  color: var(--fg);
  font-size: clamp(34px, 4vw, 52px);
  font-weight: 610;
  letter-spacing: -0.045em;
  line-height: 1.18;
}

.app-intro .badge {
  display: inline-flex;
  margin-top: 18px;
  padding: 7px 10px;
  border: 1px solid var(--border-strong);
  border-radius: 0;
  background: rgba(90, 169, 255, 0.055);
  color: var(--muted);
  font-size: 10px;
  font-weight: 650;
  letter-spacing: 0.09em;
}

body.app-page .card,
body.app-page .section,
body.app-page .leaderboard-container {
  border-color: var(--border-strong);
  border-radius: 0;
  background:
    radial-gradient(circle at 90% 0, rgba(90, 169, 255, 0.08), transparent 28%),
    linear-gradient(140deg, rgba(11, 23, 30, 0.98), rgba(7, 16, 21, 0.98));
  box-shadow: 0 24px 64px rgba(0, 0, 0, 0.16);
}

body.app-page .section,
body.app-page .card {
  padding: clamp(20px, 3vw, 30px);
}

body.app-page input,
body.app-page select,
body.app-page textarea,
body.app-page button,
body.app-page .ghost {
  border-color: var(--border-strong);
}

body.app-page input,
body.app-page select,
body.app-page textarea {
  background-color: rgba(4, 10, 14, 0.74);
}

body.app-page button.primary,
body.app-page .mode-tab.active,
body.app-page .seg input:checked + label {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--canvas-deep);
}

body.app-page button:hover,
body.app-page button:focus-visible {
  border-color: var(--accent);
}

body.app-page .app-about {
  margin-top: 48px;
  padding-top: 36px;
  border-top: 1px solid var(--border-strong);
  color: var(--muted);
  font-size: 14px;
  line-height: 1.8;
}

body.app-page .section.app-about {
  padding-inline: 0;
  border-right: 0;
  border-bottom: 0;
  border-left: 0;
  background: transparent;
  box-shadow: none;
}

body.app-page .app-about h2 {
  margin: 30px 0 12px;
  color: var(--fg);
  font-size: 18px;
  font-weight: 610;
  letter-spacing: -0.02em;
}

body.app-page .app-about h2:first-child {
  margin-top: 0;
}

body.app-page > footer {
  width: 100%;
  margin-top: 0 !important;
  padding: 38px var(--page-x) 54px !important;
  border-top: 1px solid var(--border) !important;
  color: var(--faint) !important;
  font-size: 12px !important;
  text-align: left !important;
}

body.app-page > footer p {
  width: min(100%, var(--page-width));
  margin-inline: auto !important;
}

body.app-page > footer a {
  color: var(--muted) !important;
}

body.app-page :focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 4px;
}

.app-header-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.pong-page .app-site-header .back-link {
  margin-right: 4px;
}

.pong-page .game-container {
  min-height: 0;
}

.ranking-page main {
  padding: 50px var(--page-x) 72px;
}

.ranking-page main > .wrap {
  max-width: 800px;
  padding: 0;
}

.ranking-page .title-section {
  padding-top: 0;
}

.ranking-page .title-section::before {
  display: block;
  margin-bottom: 14px;
  color: var(--accent);
  content: "POPONG / LEADERBOARD";
  font-family: var(--font);
  font-size: 10px;
  font-weight: 650;
  letter-spacing: 0.18em;
  line-height: 1;
}

.ranking-page .title-section h1 {
  color: var(--fg);
  font-size: clamp(36px, 5vw, 52px);
  font-weight: 610;
  letter-spacing: -0.035em;
}

.ranking-page .leaderboard-header {
  background: var(--accent);
  color: var(--canvas-deep);
}

.ranking-page > .app-about {
  width: min(800px, calc(100% - (var(--page-x) * 2)));
  max-width: none !important;
  margin: 0 auto 72px !important;
  padding: 36px 0 0 !important;
}

@media (max-width: 720px) {
  :root {
    --page-x: 20px;
  }

  body.app-page::before {
    background-size: 42px 42px;
  }

  .app-site-header__inner {
    min-height: 68px;
  }

  .app-brand {
    gap: 10px;
    font-size: 13px;
  }

  .app-brand-mark {
    width: 31px;
    height: 31px;
  }

  .app-brand small {
    display: none;
  }

  .app-site-header .back-link {
    padding-inline: 12px;
  }

  .app-site-header .back-link-label {
    display: none;
  }

  .app-main {
    padding-block: 42px 60px;
  }

  .app-intro {
    margin-bottom: 28px;
    padding-bottom: 24px;
  }

  .app-intro h1 {
    font-size: clamp(28px, 9vw, 40px);
  }

  body.app-page .app-about {
    margin-top: 40px;
    padding-top: 30px;
  }

  .ranking-page main {
    padding-block: 42px 60px;
  }

  .ranking-page > .app-about {
    margin-bottom: 60px !important;
  }

  .pong-page .app-site-header__inner {
    flex-wrap: wrap;
    gap: 10px;
  }

  .pong-page .app-header-actions {
    gap: 8px;
    margin-left: auto;
  }

  .pong-page .app-brand > span:last-child {
    display: none;
  }
}