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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: #f5f5f5;
    color: #333;
}

.header {
    background: linear-gradient(135deg, #6b3fa0 0%, #5a2d8a 100%);
    color: white;
    padding: 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 15px;
}

.logo {
    height: 40px;
    width: auto;
}

.title {
    font-size: 20px;
    font-weight: 600;
}

.progress-info {
    font-size: 14px;
    opacity: 0.9;
}

.close-btn {
    background: none;
    border: none;
    color: white;
    font-size: 24px;
    cursor: pointer;
    padding: 5px;
}

.container {
    display: flex;
    height: calc(100vh - 80px);
}

.sidebar {
    width: 300px;
    background: white;
    border-right: 1px solid #e0e0e0;
    overflow-y: auto;
    padding: 20px;
}

.content-area {
    flex: 1;
    padding: 40px;
    overflow-y: auto;
    background: #fafafa;
}

.lesson-group {
    margin-bottom: 15px;
}

.group-header {
    background: #f5f5f5;
    padding: 12px 15px;
    font-weight: 600;
    color: #1a3a52;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-radius: 4px;
    user-select: none;
}

.group-header:hover {
    background: #efefef;
}

.group-header.expanded {
    background: #e8e8e8;
}

.group-toggle {
    font-size: 18px;
    transition: transform 0.2s;
}

.group-toggle.open {
    transform: rotate(90deg);
}

.lesson-item {
    padding: 12px 15px;
    margin-left: 10px;
    cursor: pointer;
    border-radius: 4px;
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 14px;
    color: #666;
    transition: all 0.2s;
    margin-top: 5px;
}

.lesson-item:hover {
    background: #f0f0f0;
    color: #1a3a52;
}

.lesson-item.active {
    background: #6b3fa0;
    color: white;
    font-weight: 500;
}

.lesson-icon {
    font-size: 16px;
}

.lesson-content {
    background: white;
    border-radius: 8px;
    padding: 40px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.lesson-title {
    font-size: 24px;
    font-weight: 600;
    color: #1a3a52;
    margin-bottom: 30px;
}

.lesson-media {
    margin-bottom: 30px;
}

.audio-player {
    width: 100%;
    margin-bottom: 20px;
}

.lesson-image {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin-bottom: 20px;
    display: block;
}

.lesson-text {
    font-size: 16px;
    line-height: 1.6;
    color: #555;
    margin-bottom: 20px;
}

.alphabet-display {
    font-size: 32px;
    font-weight: bold;
    text-align: center;
    line-height: 1.8;
    color: #1a3a52;
    margin-bottom: 30px;
}

.days-months-display {
    font-size: 18px;
    line-height: 2;
    color: #1a3a52;
}

.quiz-container {
    background: white;
    border-radius: 8px;
    padding: 40px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 2px solid #f0f0f0;
}

.quiz-title {
    font-size: 24px;
    font-weight: 600;
    color: #1a3a52;
}

.quiz-progress {
    font-size: 14px;
    color: #999;
}

.question-number {
    color: #1a3a52;
    font-weight: 600;
}

.quiz-question {
    margin-bottom: 30px;
}

.question-text {
    font-size: 18px;
    font-weight: 500;
    color: #1a3a52;
    margin-bottom: 20px;
}

.question-audio {
    margin-bottom: 20px;
    width: 100%;
}

.answer-options {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.answer-option {
    display: flex;
    align-items: center;
    padding: 15px 20px;
    border: 2px solid #e0e0e0;
    border-radius: 6px;
    cursor: pointer;
    transition: all 0.2s;
    background: white;
}

.answer-option:hover {
    border-color: #c4a747;
    background: #faf8f3;
}

.answer-option.selected {
    border-color: #c4a747;
    background: #fff9e6;
}

.answer-option input[type="radio"] {
    margin-right: 15px;
    cursor: pointer;
    width: 18px;
    height: 18px;
    accent-color: #c4a747;
}

.answer-text {
    font-size: 16px;
    color: #666;
}

.quiz-buttons {
    display: flex;
    gap: 15px;
    margin-top: 30px;
    padding-top: 20px;
    border-top: 2px solid #f0f0f0;
}

.btn {
    padding: 12px 30px;
    border: none;
    border-radius: 25px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-submit {
    background: #c4a747;
    color: white;
    flex: 1;
}

.btn-submit:hover:not(:disabled) {
    background: #b5962e;
    box-shadow: 0 2px 8px rgba(196, 167, 71, 0.3);
}

.btn-submit:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-skip {
    background: #f0f0f0;
    color: #666;
    flex: 1;
}

.btn-skip:hover {
    background: #e0e0e0;
}

.result-container {
    background: white;
    border-radius: 8px;
    padding: 60px 40px;
    text-align: center;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.result-title {
    font-size: 32px;
    font-weight: 700;
    color: #1a3a52;
    margin-bottom: 20px;
}

.result-score {
    font-size: 48px;
    font-weight: 700;
    color: #c4a747;
    margin-bottom: 10px;
}

.result-message {
    font-size: 18px;
    color: #666;
    margin-bottom: 40px;
    line-height: 1.6;
}

.result-details {
    background: #f5f5f5;
    padding: 20px;
    border-radius: 6px;
    margin-bottom: 40px;
    font-size: 14px;
    color: #666;
}

.result-button {
    padding: 15px 50px;
    background: #c4a747;
    color: white;
    border: none;
    border-radius: 25px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.result-button:hover {
    background: #b5962e;
    box-shadow: 0 2px 8px rgba(196, 167, 71, 0.3);
}

.hidden {
    display: none;
}

@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        max-height: 300px;
        border-right: none;
        border-bottom: 1px solid #e0e0e0;
    }

    .content-area {
        padding: 20px;
    }

    .lesson-content,
    .quiz-container,
    .result-container {
        padding: 20px;
    }

    .header {
        flex-direction: column;
        gap: 10px;
    }

    .header-left {
        width: 100%;
    }
}