* {margin:0; padding:0; box-sizing:border-box;}
    body {
      font-family:'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      line-height:1.6;
      color:#302f2f;
      background:linear-gradient(135deg,#667eea 0%, #764ba2 100%);
      min-height:100vh;
      padding:20px; 
    } 
    .container {
      max-width:900px;
      margin:0 auto;
      background:rgba(255,255,255,0.95);
      border-radius:20px;
      box-shadow:0 20px 40px rgba(0,0,0,0.1);
      backdrop-filter:blur(10px);
      overflow:hidden;
      padding:20px;
    }
    .back-button {
      background:linear-gradient(45deg,#3498db,#2980b9);
      color:white;
      padding:12px 25px;
      border-radius:25px;
      text-decoration:none;
      margin-bottom:30px;
      display:inline-block;
    }
    .header {text-align:center; color:rgb(67,64,64);}
    .header h1 {
      font-size:3em;
      margin-bottom:10px;
      text-shadow:2px 2px 4px rgba(29,16,44,0.3);
    }
    .header p {font-size:1.2em; opacity:0.9;}
    .content {padding:40px;}
    .section {
      margin-bottom:40px;
      padding:30px;
      background:rgba(251,251,251,0.97);
      border-radius:15px;
      border-left:5px solid #4105d7;
      transition:transform 0.3s ease;
    }
    .section:hover {
      transform:translateY(-5px);
      box-shadow:0 10px 20px rgba(0,0,0,0.1);
    }
    .section h2 {
      color:#2c3e50;
      margin-bottom:20px;
      font-size:2em;
      display:flex;
      align-items:center;
      gap:10px;
    }
    .icon {
      width:30px;
      height:30px;
      border-radius:50%;
      display:inline-flex;
      align-items:center;
      justify-content:center;
    }
    .examples-grid {
      display:grid;
      grid-template-columns:repeat(auto-fit,minmax(300px,1fr));
      gap:20px;
      margin:20px 0;
    }
    .example-card {
      background:linear-gradient(135deg,#f6f6f6 0%,#ffffff 100%);
      padding:20px;
      border-radius:10px;
      box-shadow:0 5px 15px rgba(0,0,0,0.1);
    }
    .example-card h4 {color:#2c3e50; margin-bottom:10px;}
    .example-card p {margin:5px 0; font-size:1.1em;}
    .key-points {
      background:linear-gradient(135deg,#ffecd2 0%,#fcb69f 100%);
      padding:30px;
      border-radius:15px;
      margin:20px 0;
    }
    .key-points li {
      margin:15px 0;
      padding:15px;
      background:rgba(255,255,255,0.5);
      border-radius:8px;
      border-left:4px solid #ff6b6b;
      font-weight:500;
    }
    .activity {
      background:linear-gradient(135deg,#d299c2 0%,#fef9d7 100%);
      padding:30px;
      border-radius:15px;
      margin:20px 0;
    }
    .question {
      background:rgba(255,255,255,0.7);
      padding:15px;
      margin:15px 0;
      border-radius:8px;
      border-left:4px solid #9b59b6;
    }
    .option-btn {
      display:block;
      width:100%;
      margin:8px 0;
      padding:12px;
      border-radius:8px;
      border:none;
      cursor:pointer;
      background:#cce5ff; /* fondo azul claro */
      font-size:1em;
      font-weight:500;
      transition:0.2s;
    }
    .option-btn:hover {background:#99ccff;}
    .result {
      margin:10px 0;
      padding:10px;
      border-radius:5px;
      font-weight:bold;
    }
    .correct {
      background:#d4edda;
      color:#155724;
      border:1px solid #c3e6cb;
    }
    .incorrect {
      background:#f8d7da;
      color:#721c24;
      border:1px solid #f5c6cb;
    }