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

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.6;
            background: #2c5f41;
            color: #333;
            min-height: 100vh;
        }

         .container {
            max-width: 900px;
            margin: 0px auto;
            background: rgba(255, 255, 255, 0.95);
            /* border-radius: 20px; */
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
            overflow: hidden;
            /* backdrop-filter: blur(10px); */
        }

        .header {
            background: #2c3e50;
            color: white;
            padding: 40px 30px;
            text-align: center;
            position: relative;
            overflow: hidden;
        }

        .header h1 {
            font-size: 2.5em;
            margin-bottom: 10px;
            text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
        }

        .header p {
            font-size: 1.2em;
            opacity: 0.9;
        }

        .content-card {
            background: white;
            border-radius: 15px;
            padding: 30px;
            margin-bottom: 25px;
            box-shadow: 0 10px 30px rgba(0,0,0,0.1);
            transition: transform 0.3s ease;
        }

        .content-card:hover {
            transform: translateY(-5px);
        }

        .section-title {
            color: #5a67d8;
            font-size: 1.8em;
            margin-bottom: 20px;
            border-bottom: 3px solid #e2e8f0;
            padding-bottom: 10px;
        }

        .formula-box {
            background: #4a5d7a;
            color: white;
            padding: 20px;
            border-radius: 10px;
            margin: 20px 0;
            text-align: center;
            box-shadow: 0 5px 15px rgba(74, 93, 122, 0.3);
        }

        .formula {
            font-size: 1.3em;
            font-weight: bold;
            margin: 10px 0;
        }

        .tip-box {
            background: linear-gradient(135deg, #ffecd2 0%, #fcb69f 100%);
            padding: 15px;
            border-radius: 8px;
            margin: 15px 0;
            border-left: 4px solid #ff8a65;
        }

        .example-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(450px, 1fr));
            gap: 20px;
            margin-top: 20px;
        }

        .example {
            background: #f8fafc;
            border: 2px solid #e2e8f0;
            border-radius: 10px;
            padding: 20px;
            transition: all 0.3s ease;
        }

        .example:hover {
            border-color: #5a67d8;
            background: #f1f5f9;
        }

        .example-title {
            color: #2d3748;
            font-size: 1.2em;
            font-weight: bold;
            margin-bottom: 15px;
        }

        .step {
            margin: 10px 0;
            padding: 8px 12px;
            background: white;
            border-radius: 5px;
            border-left: 3px solid #38b2ac;
        }

        .answer {
            background: linear-gradient(135deg, #48bb78 0%, #38a169 100%);
            color: white;
            padding: 12px;
            border-radius: 8px;
            text-align: center;
            font-weight: bold;
            font-size: 1.1em;
            margin-top: 15px;
        }

        .highlight {
            background: #fed7d7;
            padding: 2px 6px;
            border-radius: 3px;
            font-weight: bold;
        }

        .interactive-section {
            background: linear-gradient(135deg, #e0e7ff 0%, #c7d2fe 100%);
            border-radius: 10px;
            padding: 20px;
            margin-top: 20px;
        }

        .calculator {
            background: white;
            padding: 20px;
            border-radius: 8px;
            margin-top: 15px;
        }

        .input-group {
            margin: 15px 0;
        }

        .input-group label {
            display: block;
            margin-bottom: 5px;
            font-weight: bold;
            color: #4a5568;
        }

        .input-group input, .input-group select {
            width: 100%;
            padding: 10px;
            border: 2px solid #e2e8f0;
            border-radius: 5px;
            font-size: 1em;
        }

        .input-group input:focus, .input-group select:focus {
            outline: none;
            border-color: #5a67d8;
        }

        .calculate-btn {
            background: linear-gradient(135deg, #5a67d8 0%, #667eea 100%);
            color: white;
            padding: 12px 24px;
            border: none;
            border-radius: 8px;
            font-size: 1.1em;
            cursor: pointer;
            transition: all 0.3s ease;
        }

        .calculate-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 5px 15px rgba(90, 103, 216, 0.4);
        }

        .result {
            margin-top: 15px;
            padding: 15px;
            background: #f0fff4;
            border: 2px solid #68d391;
            border-radius: 8px;
            display: none;
        }

        .fraction {
            display: inline-block;
            text-align: center;
            vertical-align: middle;
        }

        .numerator {
            display: block;
            border-bottom: 1px solid;
            padding-bottom: 2px;
        }

        .denominator {
            display: block;
            padding-top: 2px;
        }

        /* Quiz Styles */
        .quiz-container {
            background: rgba(255, 255, 255, 0.95);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            box-shadow: 0 20px 40px rgba(0, 0, 0, 0.1);
            padding: 40px;
            max-width: 700px;
            margin: 40px auto;
            animation: slideUp 0.6s ease-out;
        }

        @keyframes slideUp {
            from {
                opacity: 0;
                transform: translateY(30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }

        .quiz-title {
            text-align: center;
            color: #333;
            margin-bottom: 30px;
            font-size: 2.2em;
            background: linear-gradient(45deg, #4ade80, #22d3ee);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
        }

        .progress-bar {
            background: #e0e0e0;
            height: 8px;
            border-radius: 4px;
            margin-bottom: 30px;
            overflow: hidden;
        }

        .progress-fill {
            background: linear-gradient(90deg, #667eea, #764ba2);
            height: 100%;
            width: 0%;
            transition: width 0.3s ease;
            border-radius: 4px;
        }

        .question-container {
            margin-bottom: 30px;
            padding: 25px;
            background: #f8f9ff;
            border-radius: 15px;
            border-left: 5px solid #667eea;
        }

        .question {
            font-size: 1.2em;
            margin-bottom: 20px;
            color: #333;
            font-weight: 500;
        }

        .options {
            display: grid;
            gap: 12px;
        }

        .option {
            background: white;
            border: 2px solid #e0e0e0;
            border-radius: 10px;
            padding: 15px 20px;
            cursor: pointer;
            transition: all 0.3s ease;
            font-size: 1em;
            display: flex;
            align-items: center;
        }

        .option:hover {
            border-color: #667eea;
            background: #f0f4ff;
            transform: translateX(5px);
        }

        .option.selected {
            border-color: #667eea;
            background: #e8f0ff;
        }

        .option.correct {
            border-color: #4caf50;
            background: #e8f5e8;
            color: #2e7d32;
        }

        .option.incorrect {
            border-color: #f44336;
            background: #ffebee;
            color: #c62828;
        }

        .submit-btn {
            background: linear-gradient(45deg, #667eea, #764ba2);
            color: white;
            border: none;
            padding: 15px 30px;
            font-size: 1.1em;
            border-radius: 25px;
            cursor: pointer;
            transition: all 0.3s ease;
            display: block;
            margin: 30px auto;
            box-shadow: 0 5px 15px rgba(102, 126, 234, 0.3);
        }

        .submit-btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
        }

        .submit-btn:disabled {
            background: #ccc;
            cursor: not-allowed;
            transform: none;
            box-shadow: none;
        }

        .feedback {
            margin-top: 15px;
            padding: 15px;
            border-radius: 10px;
            font-weight: 500;
            text-align: center;
        }

        .feedback.correct {
            background: #e8f5e8;
            color: #2e7d32;
            border: 1px solid #4caf50;
        }

        .feedback.incorrect {
            background: #ffebee;
            color: #c62828;
            border: 1px solid #f44336;
        }

        .score-container {
            text-align: center;
            margin-top: 30px;
            padding: 25px;
            background: linear-gradient(45deg, #667eea, #764ba2);
            color: white;
            border-radius: 15px;
        }

        .score {
            font-size: 2em;
            font-weight: bold;
            margin-bottom: 10px;
        }

        .reset-btn {
            background: white;
            color: #667eea;
            border: 2px solid white;
            padding: 12px 25px;
            font-size: 1em;
            border-radius: 20px;
            cursor: pointer;
            margin-top: 15px;
            transition: all 0.3s ease;
        }

        .reset-btn:hover {
            background: transparent;
            color: white;
        }

        .hidden {
            display: none;
        }