* {
    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;
    padding: 20px;
}

.container {
    max-width: 800px;
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 30px;
    color: white;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.card-counter {
    font-size: 1.2rem;
    background: rgba(255,255,255,0.2);
    padding: 10px 20px;
    border-radius: 25px;
    display: inline-block;
    backdrop-filter: blur(10px);
}

.flashcard-container {
    perspective: 1000px;
    margin-bottom: 30px;
    display: flex;
    justify-content: center;
}

.flashcard {
    width: 100%;
    max-width: 500px;
    height: 300px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s;
    cursor: pointer;
}

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

.card-front, .card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.3);
    background: white;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.card-back {
    transform: rotateY(180deg);
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    color: white;
}

.card-content {
    text-align: center;
    width: 100%;
}

.card-content h2 {
    margin-bottom: 20px;
    font-size: 1.5rem;
    color: #333;
}

.card-back .card-content h2 {
    color: white;
}

.card-content p {
    font-size: 1.1rem;
    line-height: 1.6;
    color: #555;
}

.card-back .card-content p {
    color: white;
}

.controls {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.nav-btn, .flip-btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s;
}

.nav-btn {
    background: #4CAF50;
    color: white;
}

.nav-btn:hover {
    background: #45a049;
    transform: translateY(-2px);
}

.nav-btn:disabled {
    background: #ccc;
    cursor: not-allowed;
    transform: none;
}

.flip-btn {
    background: #2196F3;
    color: white;
}

.flip-btn:hover {
    background: #1976D2;
    transform: translateY(-2px);
}

.action-buttons {
    display: flex;
    justify-content: center;
    gap: 15px;
    flex-wrap: wrap;
}

.action-btn {
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: all 0.3s;
    background: rgba(255,255,255,0.2);
    color: white;
    backdrop-filter: blur(10px);
}

.action-btn:hover {
    background: rgba(255,255,255,0.3);
    transform: translateY(-2px);
}

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

.modal-content {
    background-color: white;
    margin: 5% auto;
    padding: 0;
    border-radius: 15px;
    width: 90%;
    max-width: 500px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
    animation: modalSlideIn 0.3s ease-out;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(-50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-header {
    padding: 20px;
    border-bottom: 1px solid #eee;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h2 {
    color: #333;
    margin: 0;
}

.close {
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    color: #aaa;
    line-height: 1;
}

.close:hover {
    color: #333;
}

.modal-body {
    padding: 20px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
    color: #333;
}

.form-group textarea {
    width: 100%;
    padding: 12px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 1rem;
    resize: vertical;
    transition: border-color 0.3s;
}

.form-group textarea:focus {
    outline: none;
    border-color: #2196F3;
}

.modal-footer {
    padding: 20px;
    border-top: 1px solid #eee;
    display: flex;
    justify-content: flex-end;
    gap: 10px;
}

.btn-primary, .btn-secondary {
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s;
}

.btn-primary {
    background: #2196F3;
    color: white;
}

.btn-primary:hover {
    background: #1976D2;
}

.btn-secondary {
    background: #f5f5f5;
    color: #333;
}

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

/* Responsive Design */
@media (max-width: 600px) {
    header h1 {
        font-size: 2rem;
    }
    
    .flashcard {
        height: 250px;
    }
    
    .card-content h2 {
        font-size: 1.3rem;
    }
    
    .card-content p {
        font-size: 1rem;
    }
    
    .controls {
        flex-direction: column;
        align-items: center;
    }
    
    .nav-btn, .flip-btn {
        width: 100%;
        max-width: 200px;
    }
}