:root {
        --primary-color: #4e54c8;
        --secondary-color: #8f94fb;
        --accent-color: #00d2ff;
        --success-color: #198754;
        --danger-color: #dc3545;
        --text-dark: #1a1d20;
        --text-light: #6c757d;
        --glass-bg: rgba(255, 255, 255, 0.95);
        --glass-border: 1px solid rgba(255, 255, 255, 0.2);
        --shadow-soft: 0 10px 30px rgba(0, 0, 0, 0.08);
        --radius-xl: 20px;
        --radius-md: 12px;
    }

    body {
        font-family: 'Be Vietnam Pro', sans-serif;
        background: #4e54c8;
        background: linear-gradient(135deg, #8f94fb 0%, #4e54c8 100%);
        min-height: 100vh;
        display: flex;
        flex-direction: column;
        color: var(--text-dark);
    }

    /* --- Navbar Styling --- */
    .navbar {
        background: rgba(255, 255, 255, 0.9);
        backdrop-filter: blur(10px);
        box-shadow: 0 2px 15px rgba(0,0,0,0.05);
        padding: 15px 0;
    }
    .navbar-brand {
        font-weight: 700;
        color: var(--primary-color) !important;
        font-size: 1.4rem;
    }
    .nav-link {
        font-weight: 500;
        color: var(--text-dark) !important;
        margin: 0 10px;
        transition: color 0.3s;
        cursor: pointer;
    }
    .nav-link:hover, .nav-link.active {
        color: var(--primary-color) !important;
    }
    .nav-btn-donate {
        background: var(--primary-color);
        color: white !important;
        padding: 8px 20px;
        border-radius: 20px;
        box-shadow: 0 4px 10px rgba(78, 84, 200, 0.3);
    }
    .nav-btn-donate:hover {
        background: var(--secondary-color);
        transform: translateY(-2px);
    }

    /* --- Main Content --- */
    .main-content {
        flex: 1;
        display: flex;
        align-items: flex-start;
        justify-content: center;
        padding: 40px 20px;
    }

    .content-wrapper {
        width: 100%;
        max-width: 800px;
        animation: fadeIn 0.5s ease-out;
    }

    .custom-card {
        background: var(--glass-bg);
        backdrop-filter: blur(10px);
        border-radius: var(--radius-xl);
        border: var(--glass-border);
        box-shadow: var(--shadow-soft);
        overflow: hidden;
        margin-bottom: 25px;
    }

    /* --- Score Page Specifics --- */
    /* 1. Circular Progress Chart */
    .score-circle-container {
        position: relative;
        width: 150px;
        height: 150px;
        margin: 0 auto;
    }
    .circular-chart {
        width: 100%;
        height: 100%;
        border-radius: 50%;
        background: conic-gradient(var(--primary-color) 0% 0%, #e0e0e0 0% 100%);
        display: flex;
        align-items: center;
        justify-content: center;
        box-shadow: inset 0 0 10px rgba(0,0,0,0.1);
        transition: background 1s ease-out;
    }
    .inner-circle {
        width: 80%;
        height: 80%;
        background-color: white;
        border-radius: 50%;
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        box-shadow: 0 5px 15px rgba(0,0,0,0.05);
    }
    .score-number { font-size: 2.5rem; font-weight: 800; line-height: 1; color: var(--primary-color); }
    .score-label { font-size: 0.8rem; color: var(--text-light); text-transform: uppercase; font-weight: 600; }

    /* 2. Question Item Styling */
    .question-item {
        border: 1px solid #eee;
        border-radius: 12px;
        margin-bottom: 20px;
        overflow: hidden;
        background: white;
        transition: all 0.3s;
    }
    
    .question-item.correct {
        border-color: #d1e7dd;
        background-color: #f8fffb;
    }
    .question-item.correct .q-header {
        background-color: rgba(25, 135, 84, 0.1);
        color: var(--success-color);
        border-bottom: 1px solid #d1e7dd;
    }
    
    .question-item.wrong {
        border-color: #f8d7da;
        background-color: #fff5f5;
    }
    .question-item.wrong .q-header {
        background-color: rgba(220, 53, 69, 0.1);
        color: var(--danger-color);
        border-bottom: 1px solid #f8d7da;
    }
    
    .q-header {
        padding: 10px 20px;
        font-weight: 700;
        display: flex;
        justify-content: space-between;
        align-items: center;
    }
    .q-body {
        padding: 20px;
        font-size: 1rem;
        line-height: 1.6;
    }
    .q-body img { max-width: 100%; height: auto; border-radius: 8px; margin: 10px 0; }
    
    /* --- Option List Styles --- */
    .option-list {
        margin-top: 15px;
        padding-top: 15px;
        border-top: 1px dashed rgba(0,0,0,0.1);
    }
    .option-item {
        display: flex;
        align-items: flex-start;
        margin-bottom: 8px;
        padding: 8px 12px;
        background-color: rgba(255, 255, 255, 0.6);
        border-radius: 6px;
        transition: background-color 0.2s;
    }
    .option-item:hover {
        background-color: rgba(255, 255, 255, 0.9);
    }
    .option-label {
        font-weight: 700;
        margin-right: 10px;
        min-width: 25px;
    }
    .option-content p { margin-bottom: 0; }
    
    /* Đổi màu nền option cho câu sai */
    .question-item.wrong .option-item {
        background-color: rgba(255, 255, 255, 0.4);
    }

    /* --- Common Styles --- */
    .exam-item {
        display: flex; justify-content: space-between; align-items: center;
        padding: 15px 20px; background: white; border-bottom: 1px solid #f0f0f0; gap: 15px;
    }
    .exam-item:hover { background-color: #f8f9fa; }
    .exam-name { font-weight: 500; display: flex; align-items: flex-start; gap: 10px; line-height: 1.4; }
    .exam-name i { color: var(--secondary-color); margin-top: 4px; }
    
    .exam-detail-btn {
        background-color: white; color: var(--primary-color);
        border: 1px solid var(--primary-color); padding: 8px 0;
        border-radius: 20px; font-size: 0.85rem; font-weight: 600;
        white-space: nowrap; min-width: 110px; text-align: center;
        flex-shrink: 0; cursor: pointer; transition: all 0.2s;
    }
    .exam-detail-btn:hover { background-color: var(--primary-color); color: white; }

    .page-section { display: none; }
    .page-section.active { display: block; animation: fadeInUp 0.4s ease-out; }
    @keyframes fadeInUp { from { opacity: 0; transform: translateY(20px); } to { opacity: 1; transform: translateY(0); } }
    
    .stat-box {
        text-align: center; padding: 15px;
        background: rgba(255,255,255,0.5); border-radius: 12px;
    }
    .stat-value { font-size: 1.2rem; font-weight: 700; }
    .stat-label { font-size: 0.8rem; color: #666; }