body {
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.nav-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    padding: 1rem 2rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
}

.home-btn {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 0.5rem;
    transition: all 0.3s ease;
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.home-btn:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
    text-decoration: none;
    color: white;
}

.game-title {
    color: white;
    margin: 0;
    font-size: 1.8rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.game-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem;
    width: 100%;
    box-sizing: border-box;
}

.status-bar {
    display: flex;
    justify-content: space-around;
    background: rgba(255, 255, 255, 0.9);
    padding: 1rem;
    border-radius: 1rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.stat-item {
    text-align: center;
}

.stat-label {
    display: block;
    font-size: 0.9rem;
    color: #666;
    margin-bottom: 0.25rem;
}

.stat-value {
    display: block;
    font-size: 1.5rem;
    font-weight: bold;
    color: #333;
}

#timer {
    color: #e74c3c;
}

#score {
    color: #27ae60;
}

#streak {
    color: #f39c12;
}

.game-area {
    flex: 1;
    display: flex;
    flex-direction: column;
    position: relative;
}

.question-display {
    background: white;
    border-radius: 1rem;
    padding: 3rem 2rem;
    text-align: center;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
    margin-bottom: 2rem;
}

.question {
    font-size: 2.5rem;
    font-weight: bold;
    color: #333;
    margin-bottom: 2rem;
    min-height: 3rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.answer-section {
    display: flex;
    gap: 1rem;
    justify-content: center;
    align-items: center;
    margin-bottom: 1rem;
}

#answer-input {
    font-size: 1.5rem;
    padding: 0.75rem 1rem;
    border: 2px solid #ddd;
    border-radius: 0.5rem;
    width: 200px;
    text-align: center;
    transition: border-color 0.3s ease;
}

#answer-input:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 10px rgba(102, 126, 234, 0.3);
}

.submit-btn {
    font-size: 1.5rem;
    padding: 0.75rem 1rem;
    background: #27ae60;
    color: white;
    border: none;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
    min-width: 50px;
}

.submit-btn:hover:not(:disabled) {
    background: #219a52;
    transform: translateY(-2px);
}

.submit-btn:disabled {
    background: #bdc3c7;
    cursor: not-allowed;
}

.feedback {
    font-size: 1.2rem;
    font-weight: bold;
    min-height: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
}

.feedback.correct {
    color: #27ae60;
}

.feedback.incorrect {
    color: #e74c3c;
}

.start-screen, .game-over-screen {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: white;
    border-radius: 1rem;
    padding: 3rem 2rem;
    text-align: center;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.start-screen h3, .game-over-screen h3 {
    color: #333;
    font-size: 2rem;
    margin-bottom: 1rem;
}

.start-screen p {
    color: #666;
    font-size: 1.2rem;
    margin-bottom: 2rem;
}

.difficulty-selector {
    margin-bottom: 2rem;
}

.difficulty-selector label {
    display: block;
    margin-bottom: 0.5rem;
    color: #333;
    font-weight: bold;
}

.difficulty-selector select {
    font-size: 1.1rem;
    padding: 0.5rem 1rem;
    border: 2px solid #ddd;
    border-radius: 0.5rem;
    background: white;
}

.start-btn, .play-again-btn {
    font-size: 1.3rem;
    padding: 1rem 2rem;
    background: #667eea;
    color: white;
    border: none;
    border-radius: 0.5rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.start-btn:hover, .play-again-btn:hover {
    background: #5a67d8;
    transform: translateY(-2px);
}

.final-stats {
    background: #f8f9fa;
    padding: 2rem;
    border-radius: 0.5rem;
    margin-bottom: 2rem;
    border-left: 4px solid #667eea;
}

.final-stats h4 {
    margin: 0 0 1rem 0;
    color: #333;
}

.final-stats p {
    margin: 0.5rem 0;
    color: #666;
}

.progress-container {
    height: 10px;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 5px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, #27ae60, #2ecc71);
    width: 0%;
    transition: width 0.1s ease;
}

.hidden {
    display: none !important;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    .nav-header {
        padding: 0.75rem 1rem;
    }
    
    .game-title {
        font-size: 1.4rem;
    }
    
    .game-container {
        padding: 1rem;
    }
    
    .status-bar {
        padding: 0.75rem;
    }
    
    .stat-value {
        font-size: 1.2rem;
    }
    
    .question {
        font-size: 2rem;
        margin-bottom: 1.5rem;
    }
    
    .question-display {
        padding: 2rem 1rem;
    }
    
    .answer-section {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    #answer-input {
        width: 100%;
        max-width: 250px;
    }
}

@media (max-width: 480px) {
    .nav-header {
        padding: 0.5rem;
    }
    
    .game-title {
        font-size: 1.2rem;
    }
    
    .game-container {
        padding: 0.5rem;
    }
    
    .question {
        font-size: 1.5rem;
    }
    
    .question-display {
        padding: 1.5rem 0.75rem;
    }
    
    #answer-input {
        font-size: 1.2rem;
        padding: 0.5rem;
    }
    
    .submit-btn {
        font-size: 1.2rem;
        padding: 0.5rem 0.75rem;
    }
}