:root {
    --bg-color: #f8f9fa;
    --card-bg: #ffffff;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --accent-color: #3b82f6;
    --accent-hover: #2563eb;
    --border-color: #e5e7eb;
    --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);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #111827;
        --card-bg: #1f2937;
        --text-primary: #f3f4f6;
        --text-secondary: #9ca3af;
        --accent-color: #60a5fa;
        --accent-hover: #93c5fd;
        --border-color: #374151;
    }
}

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

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    max-width: 1024px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
.main-header {
    text-align: center;
    margin-bottom: 4rem;
    padding-top: 2rem;
}

.logo h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.05em;
    margin-bottom: 0.5rem;
}

.logo-icon {
    font-size: 2.5rem;
    margin-right: 0.5rem;
    vertical-align: middle;
}

.accent {
    color: var(--accent-color);
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    font-weight: 400;
}

/* Main Grid */
.grid-container {
    flex: 1;
}

.category-section {
    margin-bottom: 3rem;
}

.category-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
    display: inline-block;
    color: var(--text-primary);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
}

/* Tool Card */
.tool-card {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 1rem;
    padding: 1.5rem;
    text-decoration: none;
    color: inherit;
    transition: all 0.2s ease;
    display: flex;
    flex-direction: column;
    height: 100%;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
}

.tool-card:hover:not(.placeholder) {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-color);
}

.card-icon {
    font-size: 2rem;
    margin-bottom: 1rem;
}

.card-content h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.card-content p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.card-link {
    font-weight: 600;
    color: var(--accent-color);
    font-size: 0.9rem;
    display: flex;
    align-items: center;
}

/* Placeholder Card */
.tool-card.placeholder {
    opacity: 0.7;
    background-color: transparent;
    border-style: dashed;
    cursor: default;
}

.tool-card.placeholder:hover {
    transform: none;
    box-shadow: none;
}

/* Footer */
.main-footer {
    margin-top: 4rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border-color);
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.footer-links {
    margin-top: 0.5rem;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
}

.footer-links a:hover {
    color: var(--accent-color);
}

.separator {
    margin: 0 0.5rem;
    color: var(--border-color);
}

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