:root {
    --primary-color: #4a90e2;
    --background-color: #ffffff;
    --text-color: #333333;
    --card-background: #f5f5f5;
    --card-hover: #e0e0e0;
    --header-background: #f8f9fa;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
    --primary-color: #64b5f6;
    --background-color: #1a1a1a;
    --text-color: #ffffff;
    --card-background: #2d2d2d;
    --card-hover: #3d3d3d;
    --header-background: #2d2d2d;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: 'Segoe UI', 'Meiryo UI', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 3rem;
    padding: 1rem;
    background-color: var(--header-background);
    border-radius: 10px;
    box-shadow: 0 2px 4px var(--shadow-color);
}

h1 {
    font-size: 2rem;
    color: var(--primary-color);
}

.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.5rem;
    padding: 0.5rem;
    border-radius: 50%;
    transition: background-color 0.3s;
}

.theme-toggle:hover {
    background-color: var(--card-hover);
}

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

.app-card {
    text-decoration: none;
    color: var(--text-color);
    background-color: var(--card-background);
    border-radius: 15px;
    overflow: hidden;
    transition: transform 0.3s, box-shadow 0.3s;
    box-shadow: 0 4px 6px var(--shadow-color);
}

.app-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 6px 12px var(--shadow-color);
}

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

.card-content h2 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.5rem;
}

.card-content p {
    margin-bottom: 1.5rem;
    opacity: 0.9;
}

.card-icon {
    font-size: 3rem;
    margin-top: 1rem;
}

@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }
    
    header {
        flex-direction: column;
        text-align: center;
        gap: 1rem;
    }
    
    .app-grid {
        grid-template-columns: 1fr;
    }
}