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

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.6;
            padding: 2rem;
            background-color: #f0f0f0;
            color: #333;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
        }

        h1 {
            color: #2c3e50;
            text-align: center;
            margin-bottom: 2rem;
            font-size: 2.5rem;
            text-transform: uppercase;
            letter-spacing: 2px;
            position: relative;
            padding-bottom: 1rem;
        }

        h1::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 50%;
            transform: translateX(-50%);
            width: 100px;
            height: 4px;
            background: linear-gradient(to right, #3498db, #2ecc71);
        }

        .unit-section {
            background-color: white;
            padding: 2rem;
            margin-bottom: 2rem;
            border-radius: 15px;
            box-shadow: 0 4px 15px rgba(0,0,0,0.1);
            transition: all 0.3s ease;
            position: relative;
            overflow: hidden;
        }

        .unit-section::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 4px;
            background: linear-gradient(to right, #3498db, #2ecc71);
            transform: scaleX(0);
            transition: transform 0.3s ease;
        }

        .unit-section:hover {
            transform: translateY(-5px);
        }

        .unit-section:hover::before {
            transform: scaleX(1);
        }

        .unit-section h2 {
            color: #2c3e50;
            margin-bottom: 1rem;
            font-size: 1.8rem;
        }

        .theory-section {
            background-color: #f8f9fa;
            padding: 1.5rem;
            border-radius: 10px;
            margin: 1rem 0;
            border-left: 4px solid #2ecc71;
        }

        .code-example {
            background-color: #2c3e50;
            color: #ecf0f1;
            padding: 1.5rem;
            border-radius: 10px;
            margin: 1rem 0;
            font-family: 'Courier New', monospace;
            overflow-x: auto;
            position: relative;
        }

        .code-example::before {
            content: 'Code Example';
            position: absolute;
            top: -12px;
            left: 20px;
            background-color: #2c3e50;
            padding: 0 10px;
            font-size: 0.8rem;
            color: #3498db;
        }

        .demo-box {
            background: linear-gradient(135deg, #3498db, #2ecc71);
            color: white;
            padding: 1.5rem;
            margin: 1rem 0;
            border-radius: 10px;
            text-align: center;
            cursor: pointer;
            transition: transform 0.3s ease;
        }

        .demo-box:hover {
            transform: scale(1.02);
        }

        .back-button {
            display: inline-block;
            padding: 1rem 2rem;
            background: linear-gradient(135deg, #3498db, #2ecc71);
            color: white;
            text-decoration: none;
            border-radius: 25px;
            margin-top: 2rem;
            transition: all 0.3s ease;
            box-shadow: 0 4px 15px rgba(0,0,0,0.2);
        }

        .back-button:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(0,0,0,0.2);
        }

        .viewport-demo {
            height: 50vh;
            background: linear-gradient(45deg, #2ecc71, #3498db);
            color: white;
            display: flex;
            align-items: center;
            justify-content: center;
            margin: 1rem 0;
            border-radius: 15px;
            font-size: 1.2rem;
            transition: all 0.3s ease;
        }

        .viewport-demo:hover {
            transform: scale(1.01);
        }

        .interactive-note {
            font-style: italic;
            color: #7f8c8d;
            text-align: center;
            margin-top: 1rem;
        }

         .pixel-demo-box {
            width: 200px;
            height: 100px;
        }

        .percentage-demo-box {
            width: 50%;
        }

        .rem-text {
            font-size: 2rem;
        }

        .em-parent {
            font-size: 20px;
        }

        .em-child {
            font-size: 1.5em;
        }

        .viewport-demo {
            height: 50vh;
            width: 50vw;
        }