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

:root {
    --primary-color: #4255ff;
    --primary-hover: #3d4de8;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --warning-color: #ffc107;
    --danger-color: #dc3545;
    --bg-color: #f7f8fc;
    --card-bg: #ffffff;
    --text-color: #333;
    --text-light: #666;
    --border-color: #e0e0e0;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.15);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    width: 100%;
}

/* Шапка */
.header {
    background: var(--card-bg);
    box-shadow: var(--shadow);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.logo a {
    text-decoration: none;
    color: inherit;
}

.nav {
    display: flex;
    gap: 1.5rem;
}

.nav-link {
    text-decoration: none;
    color: var(--text-color);
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    transition: all 0.2s;
}

.nav-link:hover {
    background-color: var(--bg-color);
    color: var(--primary-color);
}

.nav-link.active {
    color: var(--primary-color);
    background-color: rgba(66, 85, 255, 0.1);
}

/* Основной контент */
.main {
    flex: 1;
    padding: 2rem 0;
}

/* Поиск */
.search-section {
    text-align: center;
    margin-bottom: 3rem;
}

.search-section h2 {
    margin-bottom: 1.5rem;
    color: var(--text-color);
    font-size: 2rem;
}

.search-form {
    display: flex;
    gap: 1rem;
    max-width: 600px;
    margin: 0 auto;
}

.search-input {
    flex: 1;
    padding: 0.875rem 1.25rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

.search-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Кнопки */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    text-decoration: none;
    display: inline-block;
    text-align: center;
}

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

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow);
}

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

.btn-secondary:hover {
    background-color: #5a6268;
}

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

.btn-success:hover {
    background-color: #218838;
}

.btn-warning {
    background-color: var(--warning-color);
    color: #333;
}

.btn-warning:hover {
    background-color: #e0a800;
}

.btn-small {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

.btn-large {
    padding: 1rem 2rem;
    font-size: 1.125rem;
}

.btn-flip {
    margin-top: 1.5rem;
    width: 100%;
    max-width: 300px;
}

/* Сетка наборов */
.sets-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
    margin-top: 2rem;
}

.set-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: var(--shadow);
    transition: all 0.3s;
    display: flex;
    flex-direction: column;
}

.set-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-hover);
}

.set-title {
    margin-bottom: 0.75rem;
    font-size: 1.25rem;
}

.set-title a {
    text-decoration: none;
    color: var(--text-color);
    transition: color 0.2s;
}

.set-title a:hover {
    color: var(--primary-color);
}

.set-description {
    color: var(--text-light);
    margin-bottom: 1rem;
    flex: 1;
    font-size: 0.9rem;
}

.set-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
    color: var(--text-light);
}

.set-actions {
    margin-top: auto;
}

/* Форма создания */
.page-header {
    margin-bottom: 2rem;
}

.page-header h2 {
    font-size: 2rem;
    color: var(--text-color);
}

.create-form {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    max-width: 800px;
    margin: 0 auto;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-color);
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.875rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.2s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.cards-section {
    margin-top: 2rem;
}

.cards-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.cards-header h3 {
    font-size: 1.25rem;
}

.card-item {
    margin-bottom: 1rem;
}

.card-inputs {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.card-term,
.card-definition {
    flex: 1;
    padding: 0.75rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 0.95rem;
}

.btn-remove {
    background: var(--danger-color);
    color: white;
    border: none;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    line-height: 1;
    transition: all 0.2s;
    flex-shrink: 0;
}

.btn-remove:hover {
    background: #c82333;
    transform: scale(1.1);
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 2rem;
}

/* Режимы изучения */
.study-header {
    text-align: center;
    margin-bottom: 2rem;
}

.study-header h2 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

.study-modes {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-top: 1.5rem;
    flex-wrap: wrap;
}

.mode-btn {
    padding: 0.75rem 1.5rem;
    border: 2px solid var(--border-color);
    background: var(--card-bg);
    color: var(--text-color);
    text-decoration: none;
    border-radius: 8px;
    font-weight: 500;
    transition: all 0.2s;
}

.mode-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

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

/* Карточки (flashcards) */
.flashcards-mode {
    max-width: 600px;
    margin: 0 auto;
    text-align: center;
}

.flashcard-container {
    perspective: 1000px;
    margin-bottom: 2rem;
    height: 400px;
}

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

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

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    border-radius: 12px;
    box-shadow: var(--shadow-hover);
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--card-bg);
}

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

.flashcard-content {
    padding: 2rem;
    text-align: center;
}

.flashcard-label {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.flashcard-content h3 {
    font-size: 1.75rem;
    color: var(--text-color);
    margin-bottom: 0.5rem;
}

.flashcard-content p {
    font-size: 1.25rem;
    color: var(--text-color);
    line-height: 1.6;
}

.flashcard-controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.card-counter {
    font-weight: 500;
    color: var(--text-light);
}

/* Режим обучения */
.learn-mode,
.write-mode {
    max-width: 700px;
    margin: 0 auto;
}

.learn-card,
.write-card {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.learn-question,
.write-question {
    margin-bottom: 2rem;
}

.learn-label,
.write-label {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.learn-question h3,
.write-question h3 {
    font-size: 1.75rem;
    color: var(--text-color);
}

.learn-answer {
    margin-bottom: 2rem;
    padding-top: 2rem;
    border-top: 2px solid var(--border-color);
}

.learn-answer p {
    font-size: 1.25rem;
    color: var(--text-color);
    line-height: 1.6;
}

.learn-controls {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.learn-buttons {
    display: flex;
    gap: 1rem;
}

.learn-buttons .btn {
    flex: 1;
}

.write-input-section {
    margin-bottom: 2rem;
}

.write-input {
    width: 100%;
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    margin-bottom: 1rem;
    resize: vertical;
}

.write-input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.write-result {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 2px solid var(--border-color);
}

.result-content {
    margin-bottom: 1.5rem;
    padding: 1rem;
    border-radius: 8px;
}

.result-content.correct {
    background: rgba(40, 167, 69, 0.1);
    color: var(--success-color);
    border: 2px solid var(--success-color);
}

.result-content.incorrect {
    background: rgba(220, 53, 69, 0.1);
    color: var(--danger-color);
    border: 2px solid var(--danger-color);
}

.progress-info {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-light);
}

/* Режим теста */
.test-mode {
    max-width: 700px;
    margin: 0 auto;
}

.test-question {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    margin-bottom: 2rem;
}

.test-label {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-bottom: 1.5rem;
}

.test-question h3 {
    font-size: 1.75rem;
    margin-bottom: 2rem;
}

.test-options {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.test-option {
    padding: 1rem 1.5rem;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background: var(--card-bg);
    cursor: pointer;
    transition: all 0.2s;
    text-align: left;
}

.test-option:hover {
    border-color: var(--primary-color);
    background: rgba(66, 85, 255, 0.05);
}

.test-option.selected {
    border-color: var(--primary-color);
    background: rgba(66, 85, 255, 0.1);
}

.test-option.correct {
    border-color: var(--success-color);
    background: rgba(40, 167, 69, 0.1);
}

.test-option.incorrect {
    border-color: var(--danger-color);
    background: rgba(220, 53, 69, 0.1);
}

.test-results {
    background: var(--card-bg);
    padding: 2.5rem;
    border-radius: 12px;
    box-shadow: var(--shadow);
    text-align: center;
}

.test-results h3 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

.test-score {
    margin-bottom: 2rem;
}

.test-score p {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.test-percentage {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
}

/* Уведомления */
.alert {
    padding: 1rem 1.5rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
}

.alert-error {
    background: rgba(220, 53, 69, 0.1);
    color: var(--danger-color);
    border: 2px solid var(--danger-color);
}

.empty-state {
    text-align: center;
    padding: 3rem;
    color: var(--text-light);
}

.empty-state a {
    color: var(--primary-color);
    text-decoration: none;
}

.empty-state a:hover {
    text-decoration: underline;
}

/* Футер */
.footer {
    background: var(--card-bg);
    padding: 2rem 0;
    margin-top: auto;
    text-align: center;
    color: var(--text-light);
    border-top: 1px solid var(--border-color);
}

/* Адаптивность */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        gap: 1rem;
    }

    .nav {
        width: 100%;
        justify-content: center;
    }

    .search-form {
        flex-direction: column;
    }

    .sets-grid {
        grid-template-columns: 1fr;
    }

    .create-form {
        padding: 1.5rem;
    }

    .card-inputs {
        flex-direction: column;
    }

    .flashcard-container {
        height: 300px;
    }

    .study-modes {
        flex-direction: column;
    }

    .mode-btn {
        width: 100%;
    }

    .learn-buttons {
        flex-direction: column;
    }
}