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

:root {
    --primary-color: #2563eb;
    --secondary-color: #10b981;
    --background: #f8fafc;
    --card-background: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

header {
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2rem;
    border-bottom: 2px solid var(--border-color);
}

.tab-btn {
    padding: 0.75rem 1.5rem;
    background: none;
    border: none;
    border-bottom: 3px solid transparent;
    cursor: pointer;
    font-size: 1rem;
    color: var(--text-secondary);
    transition: all 0.3s;
    margin-bottom: -2px;
}

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

.tab-btn.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
    font-weight: 600;
}

/* Tab Content */
.tab-content {
    display: none;
}

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

.hidden {
    display: none !important;
}

/* Loading */
.loading {
    text-align: center;
    padding: 3rem;
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Learning Card */
.learning-card {
    background: var(--card-background);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
    animation: fadeIn 0.5s;
}

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

.category-badge {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: var(--primary-color);
    color: white;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.learning-card h2 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.image-container {
    margin-bottom: 1.5rem;
    border-radius: 8px;
    overflow: hidden;
}

.image-container img {
    width: 100%;
    height: auto;
    max-height: 400px;
    object-fit: cover;
    display: block;
}

.content {
    font-size: 1.1rem;
    line-height: 1.8;
    color: var(--text-primary);
    margin-bottom: 2rem;
}

.actions {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
    margin-bottom: 1rem;
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    text-decoration: none;
    display: inline-block;
}

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

.btn-primary:hover {
    background: #1d4ed8;
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.btn-secondary {
    background: var(--border-color);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: #cbd5e1;
}

.learned-status {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 1rem;
    background: #d1fae5;
    border-radius: 8px;
    color: #065f46;
    font-weight: 600;
}

.checkmark {
    font-size: 1.5rem;
}

/* Learned List */
.learned-list {
    display: grid;
    gap: 1rem;
}

.learned-item {
    background: var(--card-background);
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: var(--shadow);
    display: flex;
    gap: 1rem;
    transition: transform 0.2s;
}

.learned-item:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.learned-item-image {
    width: 120px;
    height: 120px;
    object-fit: cover;
    border-radius: 8px;
    flex-shrink: 0;
}

.learned-item-content {
    flex: 1;
}

.learned-item h3 {
    margin-bottom: 0.5rem;
    color: var(--primary-color);
}

.learned-item .category {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background: var(--border-color);
    border-radius: 12px;
    font-size: 0.875rem;
    margin-bottom: 0.5rem;
}

.learned-item .date {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* Statistics */
.stats-display {
    background: var(--card-background);
    border-radius: 12px;
    padding: 2rem;
    box-shadow: var(--shadow-lg);
}

.stat-card {
    text-align: center;
    padding: 1.5rem;
    background: var(--background);
    border-radius: 8px;
    margin-bottom: 1.5rem;
}

.stat-number {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.category-stats {
    margin-top: 2rem;
}

.category-stats h3 {
    margin-bottom: 1rem;
}

.category-stat-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
    margin-bottom: 0.5rem;
}

.category-stat-name {
    font-weight: 600;
}

.category-stat-count {
    color: var(--primary-color);
    font-weight: 600;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }

    header h1 {
        font-size: 2rem;
    }

    .tabs {
        flex-wrap: wrap;
    }

    .learning-card {
        padding: 1.5rem;
    }

    .learning-card h2 {
        font-size: 1.5rem;
    }

    .actions {
        flex-direction: column;
    }

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

    .learned-item {
        flex-direction: column;
    }

    .learned-item-image {
        width: 100%;
        height: 200px;
    }
}