/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    color: #333;
}

/* Navigation */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem 0;
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: bold;
    color: #764ba2;
}

.nav-links {
    display: flex;
    gap: 2rem;
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: #333;
    font-weight: 500;
    transition: color 0.3s;
}

.nav-links a:hover {
    color: #667eea;
}

/* Premium Button */
.premium-btn {
    background: linear-gradient(135deg, #ffd700, #ffed4e);
    color: #333;
    border: none;
    padding: 12px 24px;
    border-radius: 8px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
    box-shadow: 0 4px 15px rgba(255, 215, 0, 0.3);
}

.premium-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(255, 215, 0, 0.4);
}

/* Main Container */
.main-container {
    max-width: 800px;
    margin: 2rem auto;
    padding: 0 2rem;
}

.flashcard-app {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 20px;
    padding: 3rem;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
    text-align: center;
}

.flashcard-app h1 {
    color: #764ba2;
    margin-bottom: 2rem;
    font-size: 2.5rem;
}

/* Flashcard */
.flashcard {
    width: 300px;
    height: 200px;
    margin: 2rem auto;
    perspective: 1000px;
    cursor: pointer;
}

.flashcard-front, .flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 15px;
    font-size: 1.5rem;
    font-weight: bold;
    padding: 2rem;
    transition: transform 0.6s;
}

.flashcard-front {
    background: #f8f9fa;
    color: #495057;
    border: 3px solid #667eea;
}

.flashcard-back {
    background: #667eea;
    color: white;
    transform: rotateY(180deg);
}

.flashcard.flipped .flashcard-front {
    transform: rotateY(180deg);
}

.flashcard.flipped .flashcard-back {
    transform: rotateY(0deg);
}

/* Flashcard Controls */
.flashcard-controls {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-top: 2rem;
}

.flashcard-controls button {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    background: #764ba2;
    color: white;
    font-weight: bold;
    cursor: pointer;
    transition: background 0.3s;
}

.flashcard-controls button:hover {
    background: #5a387c;
}

/* Premium Upsell */
.premium-upsell {
    margin-top: 2rem;
}

.upsell-card {
    background: linear-gradient(135deg, #fff, #f8f9fa);
    border: 2px solid #ffd700;
    border-radius: 15px;
    padding: 2rem;
    text-align: center;
}

.upsell-card h2 {
    color: #764ba2;
    margin-bottom: 1rem;
}

.features-list {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
    margin: 2rem 0;
    text-align: left;
}

.feature {
    padding: 0.5rem;
    font-weight: 500;
}

/* Pricing */
.pricing-box {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin: 2rem 0;
}

.price-option {
    background: white;
    border: 2px solid #e9ecef;
    border-radius: 12px;
    padding: 2rem;
    text-align: center;
    transition: all 0.3s;
}

.price-option.featured {
    border-color: #667eea;
    box-shadow: 0 5px 20px rgba(102, 126, 234, 0.2);
    transform: scale(1.05);
}

.price-option h3 {
    color: #333;
    margin-bottom: 1rem;
}

.price {
    font-size: 2.5rem;
    font-weight: bold;
    color: #764ba2;
    margin: 1rem 0;
}

.price span {
    font-size: 1rem;
    color: #666;
}

.subscribe-btn {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 8px;
    font-weight: bold;
    cursor: pointer;
    width: 100%;
    transition: all 0.3s;
    margin-top: 1rem;
}

.subscribe-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    backdrop-filter: blur(5px);
}

.modal-content {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: white;
    border-radius: 15px;
    width: 90%;
    max-width: 500px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 2rem 2rem 1rem;
    border-bottom: 1px solid #e9ecef;
}

.modal-header h2 {
    color: #764ba2;
}

.close-btn {
    background: none;
    border: none;
    font-size: 2rem;
    cursor: pointer;
    color: #666;
    padding: 0;
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.close-btn:hover {
    color: #333;
}

.modal-body {
    padding: 2rem;
}

.price-display {
    font-size: 2rem;
    font-weight: bold;
    color: #764ba2;
    margin-bottom: 0.5rem;
}

.subscription-info {
    color: #666;
    margin-bottom: 2rem;
}

.email-input {
    text-align: left;
    margin-bottom: 2rem;
}

.email-input label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: #333;
}

.email-input input {
    width: 100%;
    padding: 12px;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.3s;
}

.email-input input:focus {
    outline: none;
    border-color: #667eea;
}

.pay-button {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    padding: 18px 30px;
    border-radius: 10px;
    font-size: 1.1rem;
    font-weight: bold;
    cursor: pointer;
    width: 100%;
    transition: all 0.3s;
    margin-bottom: 1rem;
}

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

.secure-notice {
    color: #666;
    font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .features-list {
        grid-template-columns: 1fr;
    }
    
    .pricing-box {
        flex-direction: column;
        align-items: center;
    }
    
    .price-option.featured {
        transform: none;
    }
    
    .modal-content {
        width: 95%;
        margin: 1rem;
    }
} 
/* Lesson Selector */
.lesson-selector {
    margin-bottom: 2rem;
    text-align: center;
}

.lesson-selector label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: bold;
    color: #764ba2;
    font-size: 1.1rem;
}

.lesson-selector select {
    padding: 12px 20px;
    border: 2px solid #667eea;
    border-radius: 8px;
    font-size: 1rem;
    width: 100%;
    max-width: 400px;
    background: white;
    cursor: pointer;
}

.lesson-selector select:focus {
    outline: none;
    border-color: #764ba2;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

/* Progress */
.progress {
    font-weight: bold;
    color: #667eea;
    margin-bottom: 1rem;
    font-size: 1.1rem;
}