:root,
:root[data-theme="light"] {
  color-scheme: light;
  --bg: #f3f5f8;
  --panel: #ffffff;
  --panel-2: #eef2f7;
  --bg-elevated: #ffffff;
  --bg-elevated-2: #eef2f7;
  --line: #dde4ec;
  --line-strong: #c5d0dd;
  --text: #132033;
  --text-soft: #2d3f56;
  --text-strong: #0f1d31;
  --muted: #607086;
  --text-muted: #607086;
  --text-quiet: #44546a;
  --primary: #2f6fe8;
  --success: #188c5f;
  --warning: #a56a00;
  --danger: #d04949;
  --primary-soft: rgba(47, 111, 232, 0.12);
  --primary-outline: rgba(47, 111, 232, 0.26);
  --surface-soft: rgba(19, 32, 51, 0.025);
  --surface-strong: rgba(19, 32, 51, 0.04);
  --bg-hover: rgba(19, 32, 51, 0.04);
  --panel-glass: rgba(255, 255, 255, 0.94);
  --nav-glass: rgba(243, 245, 248, 0.9);
  --chip-bg: rgba(19, 32, 51, 0.05);
  --hero-radial: rgba(47, 111, 232, 0.12);
  --shadow-xs: 0 4px 12px rgba(18, 31, 53, 0.04);
  --shadow-sm: 0 8px 20px rgba(18, 31, 53, 0.06);
  --shadow-md: 0 14px 30px rgba(18, 31, 53, 0.08);
  --shadow-lg: 0 22px 46px rgba(18, 31, 53, 0.1);
  --radius-sm: 12px;
  --radius-md: 18px;
  --radius-lg: 24px;
  --radius-pill: 999px;

  /* Spacing tokens */
  --space-2xs: 2px;
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 12px;
  --space-lg: 16px;
  --space-xl: 24px;
  --space-2xl: 32px;
  --space-3xl: 48px;

  /* Typography tokens */
  --text-2xs: 10px;
  --text-xs: 11px;
  --text-sm: 12.5px;
  --text-base: 14px;
  --text-md: 15px;
  --text-lg: 17px;
  --text-xl: 20px;
  --text-2xl: 26px;
  --text-3xl: 34px;

  --leading-tight: 1.3;
  --leading-normal: 1.5;
  --leading-relaxed: 1.7;
  --leading-loose: 1.85;

  --tracking-tight: -0.01em;
  --tracking-normal: 0;
  --tracking-wide: 0.02em;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #07111f;
  --panel: #0d1726;
  --panel-2: #101d30;
  --bg-elevated: #0d1726;
  --bg-elevated-2: #101d30;
  --line: #1c2a3f;
  --line-strong: #2a3f5d;
  --text: #eef4ff;
  --text-soft: #c9d7ea;
  --text-strong: #ffffff;
  --muted: #8ea2c0;
  --text-muted: #8ea2c0;
  --text-quiet: #b4c3d8;
  --primary: #5ea2ff;
  --success: #49d18c;
  --warning: #ffcc66;
  --danger: #ff7b7b;
  --primary-soft: rgba(94, 162, 255, 0.14);
  --primary-outline: rgba(94, 162, 255, 0.35);
  --surface-soft: rgba(255, 255, 255, 0.025);
  --surface-strong: rgba(255, 255, 255, 0.04);
  --bg-hover: rgba(255, 255, 255, 0.05);
  --panel-glass: rgba(13, 23, 38, 0.94);
  --nav-glass: rgba(7, 17, 31, 0.9);
  --chip-bg: rgba(255, 255, 255, 0.05);
  --hero-radial: rgba(94, 162, 255, 0.16);
  --shadow-xs: 0 8px 18px rgba(0, 0, 0, 0.12);
  --shadow-sm: 0 12px 24px rgba(0, 0, 0, 0.15);
  --shadow-md: 0 18px 36px rgba(0, 0, 0, 0.18);
  --shadow-lg: 0 24px 48px rgba(0, 0, 0, 0.22);
}

html,
body {
  min-height: 100%;
}

html {
  background: var(--bg);
}

body {
  background:
    radial-gradient(circle at top, var(--hero-radial), transparent 26%),
    linear-gradient(180deg, color-mix(in srgb, var(--bg) 94%, #fff 6%) 0%, var(--bg) 100%);
  color: var(--text);
  transition:
    background 0.22s ease,
    color 0.22s ease;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    linear-gradient(180deg, transparent 0%, rgba(255, 255, 255, 0.02) 100%),
    linear-gradient(90deg, transparent 0%, rgba(255, 255, 255, 0.018) 48%, transparent 100%);
  mix-blend-mode: soft-light;
  opacity: 0.7;
}

::selection {
  background: var(--primary-soft);
  color: var(--text-strong);
}

a,
button {
  -webkit-tap-highlight-color: transparent;
}

a:focus-visible,
button:focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 22%, transparent);
}

.page-shell {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: 18px;
  padding: 10px var(--space-md);
  border: 1px solid color-mix(in srgb, var(--line) 84%, transparent);
  border-radius: var(--radius-lg);
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--panel) 92%, transparent), color-mix(in srgb, var(--panel-2) 86%, transparent)),
    var(--panel-glass);
  box-shadow: var(--shadow-sm);
  backdrop-filter: blur(18px);
}

.page-shell.compact {
  margin-bottom: 14px;
}

.nav {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  overflow-x: auto;
  padding: var(--space-xs);
  border: 1px solid color-mix(in srgb, var(--line) 72%, transparent);
  border-radius: var(--radius-pill);
  background: color-mix(in srgb, var(--nav-glass) 94%, transparent);
  box-shadow: inset 0 1px 0 color-mix(in srgb, #fff 12%, transparent);
  backdrop-filter: blur(18px);
}

.nav::-webkit-scrollbar {
  display: none;
}

.nav-brand,
.nav-link,
.back-link,
.theme-toggle {
  text-decoration: none;
}

.nav-brand,
.nav-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  white-space: nowrap;
  min-height: 42px;
  padding: 0 var(--space-lg);
  border-radius: var(--radius-pill);
  font-size: 13px;
  font-weight: 650;
  transition:
    border-color 0.16s ease,
    background 0.16s ease,
    color 0.16s ease,
    transform 0.16s ease,
    box-shadow 0.16s ease;
}

.nav-brand {
  background: linear-gradient(180deg, color-mix(in srgb, var(--primary) 18%, transparent), color-mix(in srgb, var(--primary) 10%, transparent));
  border: 1px solid var(--primary-outline);
  color: var(--primary);
  font-weight: 800;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.nav-link {
  border: 1px solid transparent;
  background: transparent;
  color: var(--muted);
}

.nav-link:hover,
.back-link:hover,
.theme-toggle:hover {
  border-color: color-mix(in srgb, var(--line-strong) 82%, transparent);
  color: var(--text);
  transform: translateY(-1px);
}

.nav-link.active {
  background: linear-gradient(180deg, color-mix(in srgb, var(--primary) 84%, #fff 16%), var(--primary));
  color: #fff;
  box-shadow: var(--shadow-xs);
}

.nav-link.disabled {
  opacity: 0.48;
  cursor: not-allowed;
}

.back-link {
  appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  min-height: 42px;
  padding: 0 var(--space-lg);
  border: 1px solid color-mix(in srgb, var(--line) 84%, transparent);
  border-radius: var(--radius-pill);
  background:
    linear-gradient(180deg, color-mix(in srgb, var(--panel) 94%, transparent), color-mix(in srgb, var(--panel-2) 88%, transparent)),
    var(--panel);
  color: var(--muted);
  box-shadow: var(--shadow-xs);
  cursor: pointer;
  transition:
    border-color 0.16s ease,
    background 0.16s ease,
    color 0.16s ease,
    transform 0.16s ease,
    box-shadow 0.16s ease;
}

.theme-toggle {
  appearance: none;
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  padding: 0;
  border: 1px solid color-mix(in srgb, var(--line) 72%, transparent);
  border-radius: 999px;
  background: color-mix(in srgb, var(--panel) 92%, transparent);
  color: var(--muted);
  cursor: pointer;
  transition:
    border-color 0.2s ease,
    background 0.2s ease,
    transform 0.2s ease;
}

.theme-toggle:hover {
  border-color: var(--line-strong);
  background: var(--panel);
  transform: scale(1.08);
}

.theme-toggle:active {
  transform: scale(0.95);
}

/* Sun icon (light mode) */
.theme-toggle__icon {
  display: block;
  width: 16px;
  height: 16px;
  border-radius: 999px;
  background: var(--muted);
  position: relative;
  transition: all 0.3s ease;
}

/* Moon shape (dark mode) */
:root[data-theme="dark"] .theme-toggle__icon {
  background: transparent;
  box-shadow: inset -6px -2px 0 0 var(--text-muted);
  width: 14px;
  height: 14px;
}

@media (max-width: 900px) {
  .page-shell {
    flex-direction: column;
    align-items: stretch;
  }

  .back-link {
    width: 100%;
  }
}

@media (max-width: 720px) {
  .page-shell {
    padding: var(--space-sm);
    border-radius: 20px;
  }

  .nav-brand,
  .nav-link,
  .back-link {
    min-height: 40px;
    font-size: 12px;
  }
}

/* ── 520px: compact nav for small phones ── */
@media (max-width: 520px) {
  .page-shell {
    padding: var(--space-xs);
    gap: var(--space-xs);
    border-radius: 14px;
  }

  .page-shell .nav {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: none;
    flex-wrap: nowrap;
  }

  .page-shell .nav::-webkit-scrollbar {
    display: none;
  }

  .nav-brand {
    font-size: var(--text-xs);
    padding: var(--space-xs) var(--space-sm);
  }

  .nav-link {
    font-size: var(--text-xs);
    padding: var(--space-xs) var(--space-sm);
    white-space: nowrap;
  }

  .nav-brand,
  .nav-link,
  .back-link {
    min-height: 44px;
  }
}

/* ── Current page highlight via aria-current ── */
.nav-link[aria-current="page"] {
  background: linear-gradient(180deg, color-mix(in srgb, var(--primary) 84%, #fff 16%), var(--primary));
  color: #fff;
  border-color: var(--primary);
}