:root {
    --primary-color: #2980b9;
    --primary-hover: #3498db;
    --success-color: #27ae60;
    --danger-color: #e74c3c;
    --text-color: #2c3e50;
    --bg-color: #ffffff;
    --light-bg: #ecf0f1;
    --border-color: #bdc3c7;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--light-bg);
    color: var(--text-color);
    line-height: 1.6;
}

.screen {
    display: none;
    min-height: 100vh;
    padding: 20px;
}

.screen.active {
    display: flex;
}

.container {
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
}

/* Typography */
h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    text-align: center;
    margin-bottom: 1rem;
}

h2 {
    font-size: 1.8rem;
    text-align: center;
    color: #7f8c8d;
    margin-bottom: 2rem;
}

h3 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* Buttons */
.btn {
    padding: 15px 30px;
    font-size: 1.1rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 600;
    display: block;
    margin: 0 auto;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
}

.btn-secondary {
    background: #95a5a6;
    color: white;
}

.btn-secondary:hover {
    background: #7f8c8d;
}

.btn-danger {
    background: var(--danger-color);
    color: white;
}

.btn-danger:hover {
    background: #c0392b;
}

/* Info Box */
.info-box {
    background: var(--light-bg);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    padding: 25px;
    margin: 30px 0;
}

.info-box p {
    margin-bottom: 10px;
}

.info-box ul {
    margin: 15px 0;
    padding-left: 25px;
}

.info-box li {
    margin: 8px 0;
}

/* User Stats */
.user-stats {
    text-align: center;
    margin: 20px 0;
    color: #7f8c8d;
}

.user-stats p {
    margin: 5px 0;
}

/* Profile Buttons */
.profile-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-top: 20px;
}

.profile-buttons .btn {
    flex: 1;
    max-width: 250px;
}

/* Progress Bar */
.progress-bar {
    position: relative;
    width: 100%;
    height: 40px;
    background: #e0e0e0;
    border-radius: 20px;
    overflow: hidden;
    margin-bottom: 30px;
}

.progress-fill {
    height: 100%;
    background: var(--primary-color);
    transition: width 0.3s;
    border-radius: 20px;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-weight: 600;
    text-shadow: 1px 1px 2px rgba(0,0,0,0.3);
}

/* Question Container */
.question-container {
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.question-text {
    font-size: 1.2rem;
    margin-bottom: 30px;
    line-height: 1.6;
}

.question-text-small {
    font-size: 1rem;
    color: #7f8c8d;
    margin-bottom: 20px;
}

/* Answers */
.answers-container {
    margin-bottom: 30px;
}

.answer-option {
    background: white;
    border: 3px solid var(--border-color);
    border-radius: 10px;
    padding: 20px;
    margin-bottom: 15px;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
    padding-left: 60px;
}

.answer-option:hover {
    background: var(--light-bg);
    border-color: var(--primary-color);
}

.answer-option.selected {
    background: #d6eaf8;
    border-color: var(--primary-color);
}

.answer-option.correct {
    background: #d5f4e6;
    border-color: var(--success-color);
    border-width: 4px;
}

.answer-option.wrong {
    background: #fadbd8;
    border-color: var(--danger-color);
    border-width: 4px;
}

.answer-radio {
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    background: white;
}

.answer-option.selected .answer-radio {
    border-color: var(--primary-color);
}

.answer-option.selected .answer-radio::after {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: var(--primary-color);
}

.answer-icon {
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    width: 24px;
    height: 24px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 16px;
}

.answer-icon.correct {
    background: var(--success-color);
    color: white;
}

.answer-icon.wrong {
    background: var(--danger-color);
    color: white;
}

/* Feedback Screen */
.feedback-header {
    text-align: center;
    margin-bottom: 30px;
    font-size: 2rem;
}

.feedback-header.correct {
    color: var(--success-color);
}

.feedback-header.wrong {
    color: var(--danger-color);
}

/* Results Screen */
.results-box {
    background: white;
    border-radius: 15px;
    padding: 50px;
    text-align: center;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
    max-width: 600px;
    margin: 50px auto;
}

.result-status {
    font-size: 3rem;
    margin-bottom: 30px;
}

.result-status.passed {
    color: var(--success-color);
}

.result-status.failed {
    color: var(--danger-color);
}

.result-score {
    font-size: 1.8rem;
    margin-bottom: 15px;
}

.result-percentage {
    font-size: 1.5rem;
    color: #7f8c8d;
    margin-bottom: 10px;
}

.result-info {
    font-size: 0.9rem;
    color: #95a5a6;
    margin-bottom: 30px;
}

.result-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
}

.result-buttons .btn {
    flex: 1;
    max-width: 200px;
}

/* Popup */
.popup {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1000;
}

.popup.active {
    display: block;
}

.popup-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
}

.popup-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: white;
    border-radius: 15px;
    padding: 40px;
    max-width: 600px;
    width: 90%;
    max-height: 80vh;
    overflow-y: auto;
}

.stats-content {
    margin: 30px 0;
    text-align: left;
}

.stats-content p {
    margin: 15px 0;
    font-size: 1.1rem;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.3rem;
    }
    
    .question-container {
        padding: 20px;
    }
    
    .answer-option {
        padding: 15px 15px 15px 50px;
    }
    
    .results-box {
        padding: 30px 20px;
    }
    
    .result-status {
        font-size: 2rem;
    }
    
    .profile-buttons {
        flex-direction: column;
    }
    
    .profile-buttons .btn {
        max-width: 100%;
    }
    
    .result-buttons {
        flex-direction: column;
    }
    
    .result-buttons .btn {
        max-width: 100%;
    }
}

/* Loading State */
.loading {
    text-align: center;
    padding: 50px;
    font-size: 1.2rem;
    color: #7f8c8d;
}