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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    overflow-x: hidden;
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    padding-bottom: 80px;
}

#app {
    flex: 1;
    padding: 20px;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
}

.screen {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

.screen.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.screen-header {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 20px;
    padding: 25px;
    margin-bottom: 25px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.screen-header h1 {
    font-size: 2rem;
    font-weight: 700;
    color: #333;
    margin-bottom: 15px;
    text-align: center;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(100px, 1fr));
    gap: 15px;
    margin-top: 20px;
}

.stat-card {
    background: linear-gradient(135deg, #FF6B6B, #ee5a52);
    color: white;
    padding: 20px;
    border-radius: 15px;
    text-align: center;
    box-shadow: 0 4px 15px rgba(255, 107, 107, 0.3);
}

.stat-number {
    font-size: 2rem;
    font-weight: bold;
    margin-bottom: 5px;
}

.stat-label {
    font-size: 0.9rem;
    opacity: 0.9;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    background: rgba(255, 255, 255, 0.9);
    padding: 20px;
    border-radius: 15px;
    backdrop-filter: blur(10px);
}

.section-header h2 {
    color: #333;
    font-size: 1.5rem;
}

.btn-primary {
    background: linear-gradient(135deg, #FF6B6B, #ee5a52);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 25px;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(255, 107, 107, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(255, 107, 107, 0.4);
}

.btn-secondary {
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 25px;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(78, 205, 196, 0.3);
}

.btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(78, 205, 196, 0.4);
}

.btn-icon {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    padding: 10px;
    border-radius: 50%;
    cursor: pointer;
    color: white;
    transition: all 0.3s ease;
}

.btn-icon:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: scale(1.1);
}

.decks-container, .recent-activity {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 20px;
    padding: 25px;
    margin-bottom: 25px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.decks-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.deck-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 25px;
    border-radius: 15px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.deck-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
}

.deck-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 10px;
}

.deck-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 15px;
    font-size: 0.9rem;
    opacity: 0.9;
}

.deck-actions {
    display: flex;
    gap: 10px;
    margin-top: 15px;
}

.deck-actions button {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    padding: 8px 12px;
    border-radius: 20px;
    color: white;
    cursor: pointer;
    font-size: 0.8rem;
    transition: all 0.3s ease;
}

.deck-actions button:hover {
    background: rgba(255, 255, 255, 0.3);
}

.empty-state {
    grid-column: 1 / -1;
    text-align: center;
    padding: 60px 20px;
    color: #666;
}

.empty-state i {
    font-size: 4rem;
    margin-bottom: 20px;
    opacity: 0.5;
}

.empty-state p {
    font-size: 1.1rem;
    margin-bottom: 20px;
}

.deck-form, .card-form {
    background: rgba(255, 255, 255, 0.95);
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    margin-bottom: 25px;
}

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

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

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid #e1e5e9;
    border-radius: 10px;
    font-size: 1rem;
    transition: all 0.3s ease;
    background: white;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: #FF6B6B;
    box-shadow: 0 0 0 3px rgba(255, 107, 107, 0.1);
}

.form-group textarea {
    min-height: 100px;
    resize: vertical;
}

.cards-section {
    background: rgba(255, 255, 255, 0.95);
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    margin-top: 25px;
}

.form-actions {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
}

.cards-preview {
    margin-top: 25px;
    padding-top: 25px;
    border-top: 2px solid #f0f0f0;
}

.cards-list {
    display: grid;
    gap: 15px;
    margin-top: 15px;
}

.card-preview {
    background: #f8f9fa;
    padding: 15px;
    border-radius: 10px;
    border-left: 4px solid #FF6B6B;
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

.card-content-preview {
    flex: 1;
}

.card-front-preview {
    font-weight: 600;
    margin-bottom: 5px;
    color: #333;
}

.card-back-preview {
    color: #666;
    font-size: 0.9rem;
}

.card-actions {
    display: flex;
    gap: 8px;
}

.card-actions button {
    background: none;
    border: none;
    color: #666;
    cursor: pointer;
    padding: 5px;
    border-radius: 5px;
    transition: all 0.3s ease;
}

.card-actions button:hover {
    background: #e9ecef;
    color: #333;
}

.review-selection {
    background: rgba(255, 255, 255, 0.95);
    padding: 30px;
    border-radius: 20px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    text-align: center;
}

.review-decks-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 20px;
    margin-top: 25px;
}

.review-deck-card {
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    color: white;
    padding: 25px;
    border-radius: 15px;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: left;
}

.review-deck-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
}

.review-session {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 20px;
    padding: 30px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.review-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
}

.review-progress {
    display: flex;
    align-items: center;
    gap: 15px;
    flex: 1;
    margin-left: 20px;
}

.progress-bar {
    flex: 1;
    height: 8px;
    background: #e1e5e9;
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #FF6B6B, #4ECDC4);
    border-radius: 4px;
    transition: width 0.3s ease;
    width: 0%;
}

#progress-text {
    font-weight: 600;
    color: #333;
    min-width: 60px;
}

.flashcard-container {
    display: flex;
    justify-content: center;
    margin: 40px 0;
}

.flashcard {
    width: 100%;
    max-width: 500px;
    height: 300px;
    perspective: 1000px;
    position: relative;
}

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 20px;
    padding: 30px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    transition: transform 0.6s ease;
}

.flashcard-front {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.flashcard-back {
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    color: white;
    transform: rotateY(180deg);
}

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

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

.card-content {
    font-size: 1.2rem;
    line-height: 1.5;
    margin-bottom: 20px;
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

.rating-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-top: 20px;
}

.rating-btn {
    background: rgba(255, 255, 255, 0.2);
    border: none;
    padding: 15px 20px;
    border-radius: 15px;
    color: white;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    transition: all 0.3s ease;
    min-width: 80px;
}

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

.rating-btn i {
    font-size: 1.2rem;
}

.rating-btn span {
    font-size: 0.9rem;
    font-weight: 600;
}

.review-complete {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 20px;
    padding: 50px 30px;
    text-align: center;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.completion-animation {
    font-size: 4rem;
    margin-bottom: 20px;
    animation: bounce 1s ease-in-out;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-20px); }
    60% { transform: translateY(-10px); }
}

.completion-stats {
    display: flex;
    justify-content: center;
    gap: 40px;
    margin: 30px 0;
}

.stat {
    text-align: center;
}

.stat-value {
    display: block;
    font-size: 2rem;
    font-weight: bold;
    color: #FF6B6B;
    margin-bottom: 5px;
}

.stat-label {
    font-size: 0.9rem;
    color: #666;
}

.community-tabs {
    display: flex;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 15px;
    padding: 5px;
    margin-bottom: 25px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.tab-btn {
    flex: 1;
    background: none;
    border: none;
    padding: 15px 20px;
    border-radius: 10px;
    cursor: pointer;
    font-weight: 600;
    transition: all 0.3s ease;
    color: #666;
}

.tab-btn.active {
    background: linear-gradient(135deg, #FF6B6B, #ee5a52);
    color: white;
    box-shadow: 0 4px 15px rgba(255, 107, 107, 0.3);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.search-bar {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
    background: rgba(255, 255, 255, 0.95);
    padding: 20px;
    border-radius: 15px;
    backdrop-filter: blur(10px);
}

.search-bar input {
    flex: 1;
    padding: 12px 16px;
    border: 2px solid #e1e5e9;
    border-radius: 10px;
    font-size: 1rem;
}

.search-bar button {
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    border: none;
    padding: 12px 20px;
    border-radius: 10px;
    color: white;
    cursor: pointer;
    transition: all 0.3s ease;
}

.filter-tags {
    display: flex;
    gap: 10px;
    margin-bottom: 25px;
    flex-wrap: wrap;
    background: rgba(255, 255, 255, 0.95);
    padding: 20px;
    border-radius: 15px;
    backdrop-filter: blur(10px);
}

.filter-tag {
    background: #f8f9fa;
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s ease;
    color: #666;
}

.filter-tag.active {
    background: linear-gradient(135deg, #FF6B6B, #ee5a52);
    color: white;
}

.shared-decks-grid,
.my-shared-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.shared-deck-card {
    background: rgba(255, 255, 255, 0.95);
    padding: 25px;
    border-radius: 15px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
}

.shared-deck-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
}

.shared-deck-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: #333;
}

.shared-deck-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: 15px 0;
    color: #666;
    font-size: 0.9rem;
}

.share-actions {
    background: rgba(255, 255, 255, 0.95);
    padding: 20px;
    border-radius: 15px;
    margin-bottom: 25px;
    backdrop-filter: blur(10px);
    text-align: center;
}

.faq-section {
    background: rgba(255, 255, 255, 0.95);
    border-radius: 20px;
    padding: 30px;
    margin: 25px 0;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.faq-section h2 {
    text-align: center;
    margin-bottom: 30px;
    color: #333;
    font-size: 1.8rem;
}

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

.faq-item {
    border-bottom: 1px solid #e1e5e9;
    margin-bottom: 10px;
}

.faq-question {
    width: 100%;
    background: none;
    border: none;
    padding: 20px 0;
    text-align: left;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 1.1rem;
    font-weight: 600;
    color: #333;
    transition: all 0.3s ease;
}

.faq-question:hover {
    color: #FF6B6B;
}

.faq-icon {
    font-size: 1.2rem;
    font-weight: bold;
    color: #FF6B6B;
    transition: transform 0.3s ease;
}

.faq-question[aria-expanded="true"] .faq-icon {
    transform: rotate(45deg);
}

.faq-answer {
    padding: 0 0 20px 0;
    color: #666;
    line-height: 1.6;
    animation: slideDown 0.3s ease-out;
}

.faq-answer[hidden] {
    display: none;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    border-top: 1px solid rgba(255, 255, 255, 0.2);
    display: flex;
    justify-content: space-around;
    align-items: center;
    padding: 10px 0;
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.1);
    z-index: 1000;
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-decoration: none;
    color: #666;
    padding: 8px 12px;
    border-radius: 15px;
    transition: all 0.3s ease;
    min-width: 60px;
}

.nav-item.active {
    color: #FF6B6B;
    background: rgba(255, 107, 107, 0.1);
}

.nav-item i {
    font-size: 1.2rem;
    margin-bottom: 4px;
}

.nav-item span {
    font-size: 0.75rem;
    font-weight: 600;
}

.activity-container {
    max-height: 300px;
    overflow-y: auto;
}

.activity-item {
    display: flex;
    align-items: center;
    padding: 15px;
    border-radius: 10px;
    margin-bottom: 10px;
    background: #f8f9fa;
    border-left: 4px solid #4ECDC4;
}

.activity-icon {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    margin-right: 15px;
}

.activity-content {
    flex: 1;
}

.activity-title {
    font-weight: 600;
    color: #333;
    margin-bottom: 5px;
}

.activity-time {
    font-size: 0.9rem;
    color: #666;
}

footer {
    background: rgba(255, 107, 107, 0.9);
    color: white;
    text-align: center;
    padding: 20px;
    margin-top: 40px;
    backdrop-filter: blur(10px);
}

footer a {
    color: white;
    text-decoration: none;
    font-weight: 600;
}

footer a:hover {
    text-decoration: underline;
}

@media (max-width: 768px) {
    #app {
        padding: 15px;
    }
    
    .screen-header {
        padding: 20px;
    }
    
    .screen-header h1 {
        font-size: 1.5rem;
    }
    
    .stats-grid {
        grid-template-columns: repeat(3, 1fr);
        gap: 10px;
    }
    
    .stat-card {
        padding: 15px 10px;
    }
    
    .stat-number {
        font-size: 1.5rem;
    }
    
    .section-header {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    
    .decks-grid {
        grid-template-columns: 1fr;
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .flashcard {
        height: 250px;
    }
    
    .rating-buttons {
        gap: 10px;
    }
    
    .rating-btn {
        padding: 12px 15px;
        min-width: 70px;
    }
    
    .completion-stats {
        flex-direction: column;
        gap: 20px;
    }
    
    .community-tabs {
        flex-direction: column;
        gap: 5px;
    }
    
    .filter-tags {
        justify-content: center;
    }
    
    .shared-decks-grid,
    .my-shared-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .screen-header {
        padding: 15px;
    }
    
    .deck-form,
    .card-form,
    .cards-section {
        padding: 20px;
    }
    
    .flashcard-front,
    .flashcard-back {
        padding: 20px;
    }
    
    .card-content {
        font-size: 1rem;
    }
    
    .rating-buttons {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .rating-btn {
        flex: 1;
        min-width: 60px;
    }
    
    .faq-section {
        padding: 20px;
    }
    
    .nav-item span {
        font-size: 0.7rem;
    }
}

.toast {
    position: fixed;
    top: 20px;
    right: 20px;
    background: linear-gradient(135deg, #4ECDC4, #44A08D);
    color: white;
    padding: 15px 20px;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
    z-index: 1001;
    transform: translateX(400px);
    opacity: 0;
    transition: all 0.3s ease;
}

.toast.show {
    transform: translateX(0);
    opacity: 1;
}

.toast.error {
    background: linear-gradient(135deg, #FF6B6B, #ee5a52);
}

.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1002;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
}

.modal.show {
    opacity: 1;
    visibility: visible;
}

.modal-content {
    background: white;
    padding: 30px;
    border-radius: 20px;
    max-width: 500px;
    width: 90%;
    max-height: 80vh;
    overflow-y: auto;
    transform: scale(0.7);
    transition: transform 0.3s ease;
}

.modal.show .modal-content {
    transform: scale(1);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid #f0f0f0;
}

.modal-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: #333;
}

.close-modal {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #666;
    padding: 5px;
    border-radius: 50%;
    transition: all 0.3s ease;
}

.close-modal:hover {
    background: #f0f0f0;
    color: #333;
}