:root {
    --bg-color: #0a0a0a;
    --card-bg: #141414;
    --accent-color: #3d5afe;
    --text-primary: #ffffff;
    --text-secondary: #999999;
    --border-color: #222222;
    --card-hover-border: #333333;
    --glass: rgba(255, 255, 255, 0.03);
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: 'Inter', -apple-system, system-ui, sans-serif;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 80px 24px;
}

header {
    margin-bottom: 64px;
}

.brand {
    font-family: monospace;
    color: var(--accent-color);
    font-size: 0.9rem;
    margin-bottom: 12px;
    opacity: 0.8;
}

h1 {
    font-size: clamp(2.5rem, 5vw, 3.5rem);
    font-weight: 800;
    letter-spacing: -0.04em;
    margin-bottom: 16px;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
    max-width: 600px;
}

/* Filter Navigation */
.filter-nav {
    display: flex;
    gap: 12px;
    margin-top: 32px;
    flex-wrap: wrap;
}

.filter-btn {
    background: var(--glass);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 8px 18px;
    border-radius: 100px;
    cursor: pointer;
    font-size: 0.85rem;
    font-weight: 600;
    transition: all 0.2s ease;
}

.filter-btn:hover {
    border-color: var(--text-secondary);
    color: var(--text-primary);
}

.filter-btn.active {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: white;
}

/* Grid Layout */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}

/* Card Design */
.card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 32px;
    display: flex;
    flex-direction: column;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.card:hover {
    transform: translateY(-8px);
    border-color: var(--card-hover-border);
    background: #181818;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.subject-tag {
    font-size: 0.7rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--accent-color);
}

.grade-tag {
    font-size: 0.75rem;
    background: var(--border-color);
    padding: 2px 8px;
    border-radius: 4px;
    color: var(--text-secondary);
}

h3 {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 8px;
    line-height: 1.3;
}

.project-meta {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
    font-weight: 500;
}

.project-desc {
    font-size: 0.95rem;
    color: #888;
    margin-bottom: 24px;
    flex-grow: 1;
}

.card-footer {
    margin-top: auto;
}

.view-link {
    text-decoration: none;
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: gap 0.2s;
}

.view-link:hover {
    gap: 12px;
    color: var(--accent-color);
}

footer {
    margin-top: 100px;
    padding-top: 40px;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.8rem;
    text-align: center;
}

/* Responsive Tweak */
@media (max-width: 600px) {
    .container { padding: 40px 20px; }
    h1 { font-size: 2.2rem; }
}