/* :root {
    --primary-color: #0175C2;
    --secondary-color: #02569B;
    --accent-color: #13B9FD;
    --background: #f5f7fa;
    --card-bg: #ffffff;
    --text-color: #333333;
    --text-secondary: #666666;
    --header-bg: linear-gradient(135deg, #0175C2, #02569B);
    --card-shadow: 0 4px 15px rgba(0,0,0,0.08);
    --hover-shadow: 0 8px 25px rgba(0,0,0,0.12);
    --nav-bg: rgba(255, 255, 255, 0.9);
    --input-bg: #ffffff;
    --input-border: #e0e0e0;
    --footer-bg: #f0f0f0;
    --transition: all 0.3s ease;
  }
  
  [data-theme="dark"] {
    --primary-color: #13B9FD;
    --secondary-color: #0175C2;
    --accent-color: #0175C2;
    --background: #121212;
    --card-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --text-secondary: #b0b0b0;
    --header-bg: linear-gradient(135deg, #13B9FD, #0175C2);
    --card-shadow: 0 4px 15px rgba(0,0,0,0.3);
    --hover-shadow: 0 8px 25px rgba(0,0,0,0.4);
    --nav-bg: rgba(30, 30, 30, 0.9);
    --input-bg: #2d2d2d;
    --input-border: #444444;
    --footer-bg: #1a1a1a;
  }
  
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  body {
    font-family: 'Segoe UI', 'Roboto', sans-serif;
    background: var(--background);
    color: var(--text-color);
    transition: var(--transition);
    padding-top: 70px;
  } */

  :root {
    --primary-color: #0175C2;
    --secondary-color: #02569B;
    --accent-color: #13B9FD;
    --background: #f5f7fa;
    --card-bg: #ffffff;
    --text-color: #333333;
    --text-secondary: #666666;
    --header-bg: linear-gradient(135deg, #0175C2, #02569B);
    --card-shadow: 0 4px 15px rgba(0,0,0,0.08);
    --hover-shadow: 0 8px 25px rgba(0,0,0,0.12);
    --nav-bg: rgba(255, 255, 255, 0.9);
    --input-bg: #ffffff;
    --input-border: #e0e0e0;
    --footer-bg: #f0f0f0;
    --transition: all 0.3s ease;
    
    /* Card category colors */
    --beginner-color: #4CAF50;
    --intermediate-color: #FF9800;
    --advanced-color: #F44336;
  }
  
  [data-theme="dark"] {
    --primary-color: #13B9FD;
    --secondary-color: #0175C2;
    --accent-color: #0175C2;
    --background: #121212;
    --card-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --text-secondary: #b0b0b0;
    --header-bg: linear-gradient(135deg, #13B9FD, #0175C2);
    --card-shadow: 0 4px 15px rgba(0,0,0,0.3);
    --hover-shadow: 0 8px 25px rgba(0,0,0,0.4);
    --nav-bg: rgba(30, 30, 30, 0.9);
    --input-bg: #2d2d2d;
    --input-border: #444444;
    --footer-bg: #1a1a1a;
  }
  
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  body {
    font-family: 'Poppins', sans-serif;
    background: var(--background);
    color: var(--text-color);
    transition: var(--transition);
    padding-top: 70px;
    font-weight: 400;
  }
  
  /* Header Enhancement */
  header {
    background: var(--header-bg);
    color: #fff;
    padding: 4rem 1rem;
    text-align: center;
    border-radius: 0 0 30px 30px;
    margin-bottom: 2rem;
    box-shadow: 0 4px 20px rgba(0,0,0,0.15);
    position: relative;
    overflow: hidden;
  }
  
  header::before {
    content: '';
    position: absolute;
    top: -10%;
    right: -10%;
    width: 300px;
    height: 300px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 40% 60% 70% 30% / 40% 50% 60% 50%;
    z-index: 0;
  }
  
  header::after {
    content: '';
    position: absolute;
    bottom: -10%;
    left: -10%;
    width: 250px;
    height: 250px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 60% 40% 30% 70% / 60% 30% 70% 40%;
    z-index: 0;
  }
  
  header h1 {
    margin: 0 0 0.5rem;
    font-size: 2.8rem;
    font-weight: 700;
    position: relative;
    z-index: 1;
  }
  
  header p {
    font-size: 1.2rem;
    opacity: 0.9;
    max-width: 600px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
    font-weight: 300;
  }
  
  /* Card Design Improvements */
  .card {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 1.8rem;
    box-shadow: var(--card-shadow);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    height: 100%;
    position: relative;
    overflow: hidden;
    border-top: 4px solid var(--primary-color);
  }
  
  .card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url("data:image/svg+xml,%3Csvg width='100' height='100' viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M11 18c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm48 25c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm-43-7c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zm63 31c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM34 90c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zm56-76c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM12 86c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm28-65c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm23-11c2.76 0 5-2.24 5-5s-2.24-5-5-5-5 2.24-5 5 2.24 5 5 5zm-6 60c2.21 0 4-1.79 4-4s-1.79-4-4-4-4 1.79-4 4 1.79 4 4 4zm29 22c2.76 0 5-2.24 5-5s-2.24-5-5-5-5 2.24-5 5 2.24 5 5 5zM32 63c2.76 0 5-2.24 5-5s-2.24-5-5-5-5 2.24-5 5 2.24 5 5 5zm57-13c2.76 0 5-2.24 5-5s-2.24-5-5-5-5 2.24-5 5 2.24 5 5 5zm-9-21c1.105 0 2-.895 2-2s-.895-2-2-2-2 .895-2 2 .895 2 2 2zM60 91c1.105 0 2-.895 2-2s-.895-2-2-2-2 .895-2 2 .895 2 2 2zM35 41c1.105 0 2-.895 2-2s-.895-2-2-2-2 .895-2 2 .895 2 2 2zM12 60c1.105 0 2-.895 2-2s-.895-2-2-2-2 .895-2 2 .895 2 2 2z' fill='%23000000' fill-opacity='0.03' fill-rule='evenodd'/%3E%3C/svg%3E");
    opacity: 0.5;
    z-index: 0;
  }
  
  .card:hover {
    transform: translateY(-8px);
    box-shadow: var(--hover-shadow);
  }
  
  .card-content {
    position: relative;
    z-index: 1;
    flex-grow: 1;
  }
  
  .card h3 {
    margin: 0 0 1rem;
    font-size: 1.3rem;
    color: var(--primary-color);
    font-weight: 600;
    position: relative;
  }
  
  .card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1.2rem;
  }
  
  .card-tag {
    font-size: 0.7rem;
    background: rgba(1, 117, 194, 0.1);
    color: var(--primary-color);
    padding: 0.3rem 0.6rem;
    border-radius: 50px;
    font-weight: 500;
  }
  
  .card-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    margin-top: 1rem;
    padding: 0.5rem 0;
    transition: var(--transition);
    position: relative;
    z-index: 1;
  }
  
  .card-link:hover {
    color: var(--primary-color);
  }
  
  .card-link i {
    font-size: 0.8rem;
    transition: transform 0.2s ease;
  }
  
  .card-link:hover i {
    transform: translateX(5px);
  }
  
  /* Add difficulty level badges to cards */
  .card[data-level="beginner"] {
    border-top-color: var(--beginner-color);
  }
  
  .card[data-level="intermediate"] {
    border-top-color: var(--intermediate-color);
  }
  
  .card[data-level="advanced"] {
    border-top-color: var(--advanced-color);
  }
  
  
  
  nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.8rem 2rem;
    background: var(--nav-bg);
    backdrop-filter: blur(10px);
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    z-index: 1000;
    transition: var(--transition);
  }
  
  .logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 600;
    font-size: 1.2rem;
    color: var(--primary-color);
  }
  
  .logo i {
    font-size: 1.5rem;
  }
  
  .theme-toggle {
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 1.2rem;
    cursor: pointer;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
  }
  
  .theme-toggle:hover {
    background: rgba(0,0,0,0.05);
  }
  
  [data-theme="dark"] .theme-toggle:hover {
    background: rgba(255,255,255,0.1);
  }
  
  header {
    background: var(--header-bg);
    color: #fff;
    padding: 3rem 1rem;
    text-align: center;
    border-radius: 0 0 20px 20px;
    margin-bottom: 2rem;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
  }
  
  header h1 {
    margin: 0 0 0.5rem;
    font-size: 2.5rem;
    font-weight: 700;
  }
  
  header p {
    font-size: 1.1rem;
    opacity: 0.9;
    max-width: 600px;
    margin: 0 auto;
  }
  
  .search-container {
    max-width: 800px;
    margin: 0 auto 2rem;
    padding: 0 1rem;
    position: relative;
  }
  
  .search-container input {
    width: 100%;
    padding: 1rem 1.5rem;
    border: 1px solid var(--input-border);
    border-radius: 50px;
    font-size: 1rem;
    background: var(--input-bg);
    color: var(--text-color);
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    transition: var(--transition);
  }
  
  .search-container i {
    position: absolute;
    right: 1.8rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
  }
  
  .search-container input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(1, 117, 194, 0.2);
  }
  
  .filters {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    max-width: 800px;
    margin: 0 auto 1.5rem;
    padding: 0 1rem;
  }
  
  .filter-btn {
    background: var(--card-bg);
    border: 1px solid var(--input-border);
    border-radius: 50px;
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-color);
  }
  
  .filter-btn:hover, .filter-btn.active {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
  }
  
  .grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
    max-width: 1200px;
    margin: 0 auto 3rem;
    padding: 0 1rem;
  }
  
  .card {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 1.5rem;
    box-shadow: var(--card-shadow);
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    height: 100%;
    position: relative;
    overflow: hidden;
  }
  
  .card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--primary-color);
    opacity: 0;
    transition: var(--transition);
  }
  
  .card:hover {
    transform: translateY(-5px);
    box-shadow: var(--hover-shadow);
  }
  
  .card:hover::before {
    opacity: 1;
  }
  
  .card h3 {
    margin: 0 0 0.8rem;
    font-size: 1.2rem;
    color: var(--primary-color);
    transition: var(--transition);
  }
  
  .card-content {
    flex-grow: 1;
  }
  
  .card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
  }
  
  .card-tag {
    font-size: 0.7rem;
    background: rgba(1, 117, 194, 0.1);
    color: var(--primary-color);
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
  }
  
  .card-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    margin-top: 1rem;
    padding: 0.5rem 0;
    transition: var(--transition);
  }
  
  .card-link:hover {
    color: var(--primary-color);
  }
  
  .card-link i {
    font-size: 0.8rem;
    transition: transform 0.2s ease;
  }
  
  .card-link:hover i {
    transform: translateX(3px);
  }
  
  .no-results {
    text-align: center;
    grid-column: 1 / -1;
    padding: 3rem;
    color: var(--text-secondary);
  }
  
  footer {
    text-align: center;
    padding: 2rem 1rem;
    font-size: 0.9rem;
    background: var(--footer-bg);
    color: var(--text-color);
    border-top: 1px solid var(--input-border);
  }
  
  .back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 45px;
    height: 45px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: 0 2px 10px rgba(0,0,0,0.2);
    opacity: 0;
    visibility: hidden;
    transition: var(--transition);
  }
  
  .back-to-top.visible {
    opacity: 1;
    visibility: visible;
  }
  
  @media (max-width: 768px) {
    header h1 {
      font-size: 2rem;
    }
    
    .grid {
      grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    }
  }
  
  /* Animation */
  @keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
  }
  
  .card {
    animation: fadeIn 0.3s ease forwards;
  }