:root {
    --primary-color: #2563eb; 
    --secondary-color: #1e293b;
    --text-color: #475569;
    --bg-color: #f8fafc; 
    --card-bg: #ffffff;
    --hover-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

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

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

.main-header {
    background: var(--card-bg);
    padding: 2rem 0;
    box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
    margin-bottom: 3rem;
    text-align: center;
}

.logo-wrapper {
    margin-bottom: 1rem;
}

.logo-img {
    height: 60px;
    width: auto;
    object-fit: contain;
}

.header-text h1 {
    font-size: 2rem;
    font-weight: 800;
    color: var(--secondary-color);
    margin-bottom: 0.5rem;
}

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

.grid-wrapper {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 2rem;
    padding-bottom: 3rem;
}

.doc-card {
    background: var(--card-bg);
    border-radius: 16px;
    padding: 2rem;
    text-decoration: none;
    color: inherit;
    border: 1px solid #e2e8f0;
    transition: all 0.3s ease;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    position: relative;
    overflow: hidden;
}

.doc-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--hover-shadow);
    border-color: var(--primary-color);
}

.card-icon {
    width: 64px;
    height: 64px;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #eff6ff;
    border-radius: 12px;
    padding: 10px;
}

.card-icon img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

.card-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    width: 100%;
}

.tag {
    font-size: 0.75rem;
    text-transform: uppercase;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    letter-spacing: 0.05em;
}

.doc-card h2 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
    color: var(--secondary-color);
}

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

.card-footer {
    margin-top: auto;
    width: 100%;
}

.btn-link {
    display: inline-flex;
    align-items: center;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--primary-color);
    transition: transform 0.2s ease;
}

.doc-card:hover .btn-link {
    transform: translateX(5px);
}

.card-php:hover { border-color: #777BB4; }
.card-java:hover { border-color: #E76F00; }
.card-c:hover { border-color: #555555; }
.card-sql:hover { border-color: #00758F; }

footer {
    margin-top: auto;
    background: var(--card-bg);
    padding: 2rem 0;
    text-align: center;
    border-top: 1px solid #e2e8f0;
    color: var(--text-color);
    font-size: 0.9rem;
}