:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-main: #1e293b;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --radius: 12px;
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    text-align: center;
    padding: 3rem 1rem;
    background: linear-gradient(135deg, #ffffff 0%, #f1f5f9 100%);
    border-bottom: 1px solid var(--border-color);
}

header h1 {
    font-size: 2.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

header p {
    color: var(--text-muted);
    font-size: 1.1rem;
}

.tabs {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin: 2rem 0;
    padding: 0 1rem;
}

.tab-btn {
    padding: 0.75rem 2rem;
    border: none;
    background: var(--card-bg);
    color: var(--text-muted);
    font-size: 1rem;
    font-weight: 600;
    border-radius: 100px;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid transparent;
}

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

.tab-btn.active {
    background: var(--primary-color);
    color: white;
    box-shadow: var(--shadow-md);
}

main {
    flex: 1;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1.5rem 4rem;
    width: 100%;
}

.tab-content {
    display: none;
    animation: fadeIn 0.5s ease;
}

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

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

.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
}

.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
}

.card-image-wrapper {
    width: 100%;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

.card img {
    max-width: 100%;
    height: auto;
    object-fit: contain;
    border-radius: 4px;
}

.card-content {
    padding: 0.5rem;
    flex: 1;
}

.card-mnemonic {
    white-space: pre-wrap;
    font-size: 0.95rem;
    color: var(--text-main);
}

footer {
    text-align: center;
    padding: 2rem;
    background: #ffffff;
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
    font-size: 0.9rem;
}

@media (max-width: 640px) {
    header h1 {
        font-size: 2rem;
    }
    .card-grid {
        grid-template-columns: 1fr;
    }
}