:root, [data-theme="dark"] {
  --color-bg: #0f0f0f;
  --color-bg-raised: #111;
  --color-bg-surface: #1a1a1a;
  --color-bg-hover: #222;

  --color-border: #222;
  --color-border-strong: #333;

  --color-text-primary: #f0f0f0;
  --color-text-body: #e0e0e0;
  --color-text-heading: #eee;
  --color-text-secondary: #ccc;
  --color-text-muted: #bbb;
  --color-text-faint: #999;

  --color-accent-green: #4a4;
  --color-accent-yellow: #c90;
  --color-accent-red: #a44;
  --color-accent-note: #c4a8e6;

  --color-nav-bg: rgba(15, 15, 15, 0.95);
  --color-input-bg: #0f0f0f;
  --color-btn-bg: #f0f0f0;
  --color-btn-text: #0f0f0f;
  --color-btn-hover: #ddd;
  --color-card-bg: #161616;
  --color-card-header-bg: #1a1a1a;
  --color-gradient-start: #1a1a2e;
  --color-gradient-end: #16213e;
  --color-spinner-track: #222;
  --color-spinner-head: #fff;
  --color-heading-gradient: linear-gradient(135deg, #fff 0%, #888 100%);
}

[data-theme="light"] {
  --color-bg: #f8f8f8;
  --color-bg-raised: #f0f0f0;
  --color-bg-surface: #e8e8e8;
  --color-bg-hover: #ddd;

  --color-border: #ddd;
  --color-border-strong: #ccc;

  --color-text-primary: #111;
  --color-text-body: #222;
  --color-text-heading: #111;
  --color-text-secondary: #444;
  --color-text-muted: #666;
  --color-text-faint: #888;

  --color-accent-green: #2a7a2a;
  --color-accent-yellow: #b8860b;
  --color-accent-red: #c33;
  --color-accent-note: #7b5ea7;

  --color-nav-bg: rgba(248, 248, 248, 0.95);
  --color-input-bg: #fff;
  --color-btn-bg: #111;
  --color-btn-text: #f0f0f0;
  --color-btn-hover: #333;
  --color-card-bg: #fff;
  --color-card-header-bg: #f0f0f0;
  --color-gradient-start: #e8ecf4;
  --color-gradient-end: #dde4f0;
  --color-spinner-track: #ddd;
  --color-spinner-head: #111;
  --color-heading-gradient: linear-gradient(135deg, #111 0%, #666 100%);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--color-bg);
  color: var(--color-text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Nav */
nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background: var(--color-nav-bg);
  border-bottom: 1px solid var(--color-border-strong);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-brand-group {
  display: flex;
  align-items: center;
}

.nav-brand {
  text-decoration: none;
  display: flex;
  align-items: center;
}

.nav-logo {
  height: 50px;
  width: auto;
}

[data-theme="light"] .nav-logo {
  filter: invert(1);
}

.nav-divider {
  color: var(--color-text-muted);
  font-size: 1.5rem;
  font-weight: 200;
  margin: 0 0.5rem;
  opacity: 0.4;
  user-select: none;
}

.nav-brand-sub {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  font-size: 1.375rem;
  font-weight: 700;
  color: var(--color-text-heading);
}

.nav-logo-sub {
  height: 40px;
  width: auto;
}

[data-theme="light"] .nav-logo-sub {
  filter: invert(1);
}

.nav-links {
  display: flex;
  gap: 2rem;
  list-style: none;
}

.nav-links a {
  color: var(--color-text-body);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s;
}

.nav-links a:hover { color: var(--color-text-primary); }

/* Dropdown */
.dropdown {
  position: relative;
}

.dropdown > span {
  color: var(--color-text-heading);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: color 0.2s;
}

.dropdown:hover > span { color: var(--color-text-primary); }

.dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  right: 0;
  background: var(--color-bg-surface);
  border: 1px solid var(--color-border-strong);
  border-radius: 6px;
  padding: 0.5rem 0;
  min-width: 140px;
  padding-top: 0.5rem;
}

.dropdown:hover .dropdown-menu { display: block; }

.dropdown-menu a {
  display: block;
  padding: 0.4rem 1rem;
  color: var(--color-text-body);
  text-decoration: none;
  font-size: 0.85rem;
}

.dropdown-menu a:hover {
  color: var(--color-text-primary);
  background: var(--color-bg-hover);
}

.dropdown-heading {
  font-weight: 600;
  color: var(--color-text-primary) !important;
  font-size: 0.9rem !important;
  border-bottom: 1px solid var(--color-border-strong);
  padding-bottom: 0.5rem !important;
  margin-bottom: 0.25rem;
}

/* Mobile sub-links */
.mobile-label {
  color: var(--color-text-primary) !important;
  font-size: 1rem;
  font-weight: 600;
  text-decoration: none;
  padding: 0.5rem 0 0;
}

.mobile-sub {
  padding-left: 1rem !important;
}

/* Hamburger */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text-primary);
  border-radius: 2px;
  transition: 0.3s;
}

/* Mobile menu */
.mobile-menu {
  display: none;
  flex-direction: column;
  background: var(--color-bg-raised);
  border-bottom: 1px solid var(--color-border);
  padding: 1rem 2rem;
  gap: 1rem;
}

.mobile-menu.open { display: flex; }

.mobile-menu a {
  color: var(--color-text-body);
  text-decoration: none;
  font-size: 1rem;
  padding: 0.25rem 0;
}

.mobile-menu a:hover { color: var(--color-text-primary); }

/* Footer */
footer {
  padding: 3rem 2rem 1.5rem;
  color: var(--color-text-faint);
  font-size: 0.85rem;
  border-top: 1px solid var(--color-border-strong);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 2rem;
  max-width: 740px;
  margin: 0 auto 2rem;
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.footer-col h4 {
  color: var(--color-text-body);
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.footer-col a {
  color: var(--color-text-faint);
  text-decoration: none;
  font-size: 0.8rem;
  transition: color 0.2s;
}

.footer-col a:hover {
  color: var(--color-text-body);
}

.footer-bottom {
  text-align: center;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border-strong);
  color: var(--color-text-muted);
  font-size: 0.8rem;
}

@media (max-width: 600px) {
  .nav-links { display: none; }
  .hamburger { display: flex; }
  .footer-grid { grid-template-columns: repeat(2, 1fr); }
}