:root {
      --bg-color-light: #f8faff;
      --bg-color-dark: #0b0c10;
      --text-color-light: #111;
      --text-color-dark: #f8f8f2;
      --accent-color: #00ffd5;
      --feature-color: #ff4c60;
      --button-light-bg: #5c6a6e;
      --button-light-hover: #4c5658;
      --card-light: linear-gradient(145deg, #e0e8f0, #cfd8e8);
      --card-dark: linear-gradient(145deg, #1a1a2e, #16213e);
      --header-light: linear-gradient(135deg, #e0eafc, #cfdef3);
      --header-dark: linear-gradient(135deg, #141e30, #243b55);
      --border-radius: 14px;
    }

    body {
      margin: 0;
      font-family: 'Segoe UI', sans-serif;
      transition: background 0.3s, color 0.3s;
    }
    body.light-mode {
      background: var(--bg-color-light);
      color: var(--text-color-light);
    }
    body.dark-mode {
      background: var(--bg-color-dark);
      color: var(--text-color-dark);
    }

    header {
      padding: 1rem 2rem;
      display: flex;
      justify-content: space-between;
      align-items: center;
      background: var(--header-dark);
      color: white;
    }
    body.light-mode header {
      background: var(--header-light);
      color: black;
    }
    header h1 {
      margin: 0;
      font-size: 1.6rem;
    }
    nav {
      display: flex;
      gap: 1rem;
      align-items: center;
    }
    nav a,
    .bookmark-btn,
    .mode-toggle {
      text-decoration: none;
      background: var(--accent-color);
      border: none;
      padding: 0.5rem 1rem;
      border-radius: var(--border-radius);
      color: black;
      font-weight: bold;
      cursor: pointer;
      transition: background 0.2s ease, transform 0.1s;
    }
    nav a:hover,
    .bookmark-btn:hover,
    .mode-toggle:hover {
      background: #00c9aa;
    }

    .filter-section {
      margin: 1rem 2rem;
    }
    .filters-toggle {
      display: inline-flex;
      align-items: center;
      gap: 0.5rem;
      background: var(--accent-color);
      color: black;
      border: none;
      border-radius: var(--border-radius);
      padding: 0.5rem 1rem;
      font-size: 1.1rem;
      font-weight: bold;
      cursor: pointer;
      transition: background 0.2s ease, transform 0.1s;
    }
    .filters-toggle:hover {
      background: #00c9aa;
      transform: translateY(-1px);
    }
    .filters-toggle:focus {
      outline: 2px dashed var(--accent-color);
      outline-offset: 4px;
    }
    body.light-mode .filters-toggle {
      background: var(--button-light-bg);
      color: white;
    }
    body.light-mode .filters-toggle:hover {
      background: var(--button-light-hover);
      transform: translateY(-1px);
    }
    .filters-content.hidden {
      display: none;
    }

    .filters {
      display: flex;
      flex-wrap: wrap;
      gap: 1.5rem;
      padding: 1.5rem;
      background: var(--card-dark);
      border-radius: var(--border-radius);
      box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    }
    body.light-mode .filters {
      background: var(--card-light);
      box-shadow: 0 4px 12px rgba(0,0,0,0.05);
    }

    .filter-group {
      display: flex;
      flex-direction: column;
      min-width: 200px;
      flex: 1;
    }
    .filter-label {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      font-size: 1rem;
      margin-bottom: 0.5rem;
      color: var(--accent-color);
    }
    body.light-mode .filter-label {
      color: var(--text-color-light);
    }

    .filter-control {
      position: relative;
    }
    .filter-select {
      width: 100%;
      padding: 0.5rem 1rem;
      font-size: 0.95rem;
      border: 2px solid var(--accent-color);
      border-radius: var(--border-radius);
      appearance: none;
      background: transparent;
      color: black;
      cursor: pointer;
      transition: border-color 0.2s;
    }
    body.dark-mode .filter-select {
      color: #e2e2e2;
    }
    .filter-select:hover,
    .filter-select:focus {
      border-color: var(--feature-color);
      outline: none;
    }
    .filter-control::after {
      content: "\f0d7";
      font-family: "Font Awesome 6 Free";
      font-weight: 900;
      position: absolute;
      right: 1rem;
      top: 50%;
      transform: translateY(-50%);
      pointer-events: none;
      color: var(--accent-color);
    }

    .filter-checkbox-group {
      display: flex;
      flex-direction: column;
      gap: 0.5rem;
      padding: 0;
      margin: 0;
      border: none;
    }
    .custom-checkbox {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      position: relative;
      padding-left: 1.5rem;
      font-size: 0.95rem;
      cursor: pointer;
      user-select: none;
    }
    .custom-checkbox input {
      position: absolute;
      left: 0;
      top: 0;
      width: 1rem;
      height: 1rem;
      margin: 0;
      opacity: 0;
      cursor: pointer;
    }
    .custom-checkbox span::before {
      content: "";
      position: absolute;
      left: -1.5rem;
      top: 0;
      width: 1rem;
      height: 1rem;
      border: 2px solid var(--accent-color);
      border-radius: 4px;
      background: transparent;
      transition: background 0.2s, border-color 0.2s;
    }
    .custom-checkbox input:checked + span::before {
      background: var(--feature-color);
      border-color: var(--feature-color);
    }

    /* Grid: max 4 columns */
    .site-list {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 2rem;
      padding: 2.5rem;
    }
    /* Responsive fallback */
    @media (max-width: 1200px) {
      .site-list {
        grid-template-columns: repeat(3, 1fr);
      }
    }
    @media (max-width: 900px) {
      .site-list {
        grid-template-columns: repeat(2, 1fr);
      }
    }
    @media (max-width: 600px) {
      .site-list {
        grid-template-columns: repeat(1, 1fr);
      }
    }

    .site-card {
      position: relative;
      max-width: 400px;
      margin: 0 auto;
      padding: 1.75rem;
      border-radius: var(--border-radius);
      background: var(--card-dark);
      box-shadow: 0 0 12px rgba(0,255,213,0.3);
      transition: transform 0.2s;
    }
    body.light-mode .site-card {
      background: var(--card-light);
      box-shadow: 0 0 10px rgba(0,0,0,0.1);
    }
    .site-card:hover {
      transform: scale(1.02);
    }

    /* Popular badge styling */
    .badge-popular {
      position: absolute;
      top: 10px;
      right: 10px;
      background: gold;
      color: black;
      font-size: 0.75rem;
      font-weight: bold;
      padding: 0.3rem 0.6rem;
      border-radius: var(--border-radius);
      box-shadow: 0 2px 4px rgba(0,0,0,0.2);
    }

    .site-card h3 {
      margin-top: 0;
      font-size: 1.5rem;
      line-height: 1.2;
      color: var(--accent-color);
    }
    body.light-mode .site-card h3 {
      color: #333;
    }
    .site-description {
      font-size: 1rem;
      line-height: 1.4;
      margin: 0.75rem 0 1.25rem;
    }
    .features {
      display: flex;
      gap: 0.5rem;
      flex-wrap: wrap;
    }
    .feature-icon {
      background: var(--feature-color);
      padding: 0.4rem 0.6rem;
      border-radius: 6px;
      font-size: 0.85rem;
      color: white;
    }

    .cta-button {
      display: inline-block;
      margin-top: 1rem;
      padding: 0.9rem 1.5rem;
      font-size: 1rem;
      border: none;
      border-radius: var(--border-radius);
      background: var(--accent-color);
      color: black;
      font-weight: bold;
      text-decoration: none;
      box-shadow: 0 2px 6px rgba(0,0,0,0.2);
      transition: background 0.2s ease, transform 0.1s, box-shadow 0.2s;
    }
    .cta-button:hover {
      transform: translateY(-2px);
      box-shadow: 0 4px 12px rgba(0,0,0,0.2);
    }
    body.light-mode .cta-button {
      background: var(--button-light-bg);
      color: white;
      box-shadow: 0 2px 6px rgba(0,0,0,0.1);
    }
    body.light-mode .cta-button:hover {
      background: var(--button-light-hover);
      box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    }

    footer {
      text-align: center;
      padding: 2rem 1rem;
      background: var(--header-dark);
      color: white;
    }
    body.light-mode footer {
      background: var(--header-light);
      color: black;
    }