:root {
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --background-color: #f8f9fa;
    --font-color: #333;
    --card-bg: #ffffff;
    --shadow: 0 4px 8px rgba(0,0,0,0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--font-color);
    margin: 0;
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 20px;
}

header {
    text-align: center;
    margin-bottom: 40px;
}

header h1 {
    color: var(--primary-color);
    margin-bottom: 10px;
}

.grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 25px;
}

.category-card, .tool-card {
    background-color: var(--card-bg);
    border-radius: 8px;
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: transform 0.2s, box-shadow 0.2s;
    text-decoration: none;
    color: inherit;
    display: flex;
    flex-direction: column;
}

.category-card:hover, .tool-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0,0,0,0.15);
}

.category-card {
    font-size: 1.5rem;
    font-weight: bold;
    text-align: center;
    padding: 40px 20px;
    color: var(--primary-color);
}

.tool-card .card-image {
    width: 100%;
    height: 180px;
    object-fit: cover;
    background-color: #e9ecef;
}

.tool-card .card-content {
    padding: 20px;
    flex-grow: 1;
}

.tool-card h3 {
    margin-top: 0;
    margin-bottom: 10px;
    font-size: 1.2rem;
}

.tool-card p {
    margin-bottom: 0;
    font-size: 0.9rem;
    color: var(--secondary-color);
}

.back-link {
    display: inline-block;
    margin-bottom: 20px;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: bold;
}

footer {
    text-align: center;
    margin-top: 50px;
    padding-top: 20px;
    border-top: 1px solid #dee2e6;
    color: var(--secondary-color);
}