:root {
    --bg-color-light: #f0f2f5;
    --text-color-light: #1f2937;
    --card-bg-light: #ffffff;
    --card-hover-light: #e2e8f0;
    --icon-color-light: #4b5563;
    --shadow-light: rgba(0, 0, 0, 0.1);

    --bg-color-dark: #121212;
    --text-color-dark: #e5e7eb;
    --card-bg-dark: #1f2937;
    --card-hover-dark: #2d3748;
    --icon-color-dark: #a0aec0;
    --shadow-dark: rgba(255, 255, 255, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color-light);
    color: var(--text-color-light);
    transition: background-color 0.3s, color 0.3s;
    margin: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
}

body.dark-mode {
    background-color: var(--bg-color-dark);
    color: var(--text-color-dark);
}

.container {
    padding: 2rem;
    max-width: 900px;
    width: 100%;
    text-align: center;
}

.title {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: inherit;
}

.card-container {
    display: flex;
    flex-wrap: wrap;
    gap: 1.5rem;
    justify-content: center;
}

.card {
    background-color: var(--card-bg-light);
    border-radius: 12px;
    padding: 2rem;
    text-decoration: none;
    color: inherit;
    box-shadow: 0 4px 12px var(--shadow-light);
    transition: transform 0.2s, box-shadow 0.2s, background-color 0.3s;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    flex-basis: 200px;
    flex-grow: 1;
    min-width: 150px;
}

.dark-mode .card {
    background-color: var(--card-bg-dark);
    box-shadow: 0 4px 12px var(--shadow-dark);
}

.card:hover {
    transform: translateY(-5px);
    background-color: var(--card-hover-light);
    box-shadow: 0 6px 16px var(--shadow-light);
}

.dark-mode .card:hover {
    background-color: var(--card-hover-dark);
    box-shadow: 0 6px 16px var(--shadow-dark);
}

.card-icon {
    font-size: 3rem;
    color: var(--icon-color-light);
    margin-bottom: 0.75rem;
    transition: color 0.3s;
}

.dark-mode .card-icon {
    color: var(--icon-color-dark);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin: 0;
    color: inherit;
}

.theme-toggle-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.5rem;
    color: var(--text-color-light);
    transition: color 0.3s;
    z-index: 10;
}

.dark-mode .theme-toggle-btn {
    color: var(--text-color-dark);
}

.theme-toggle-btn:hover {
    opacity: 0.8;
}

@media (max-width: 600px) {
    .title {
        font-size: 2rem;
    }
    
    .card-container {
        gap: 1rem;
    }
}