:root {
    --primary: #6366f1;
    --secondary: #a855f7;
    --glass: rgba(255, 255, 255, 0.8);
    --border: rgba(255, 255, 255, 0.4);
    --text: #1f2937;
    --input-bg: #f8fafc;
}
* { box-sizing: border-box; transition: all 0.3s ease; }
body {
    font-family: 'Inter', sans-serif;
    background: #f8fafc;
    margin: 0;
    color: var(--text);
}
.blob, .blob-2 {
    position: fixed; width: 500px; height: 500px;
    filter: blur(100px); border-radius: 50%; z-index: -1; opacity: 0.15;
}
.blob { top: -100px; right: -100px; background: var(--primary); }
.blob-2 { bottom: -100px; left: -100px; background: var(--secondary); }
nav {
    display: flex; justify-content: space-between; align-items: center;
    padding: 1rem 5%; background: var(--glass);
    backdrop-filter: blur(12px); position: sticky; top: 0; z-index: 100;
    border-bottom: 1px solid var(--border);
}
.logo { font-size: 1.6rem; font-weight: 800; }
.logo span { color: var(--primary); }
.nav-controls { display: flex; gap: 12px; align-items: center; }
#searchInput {
    padding: 10px 16px; border-radius: 12px; border: 1px solid #e2e8f0; width: 250px;
}
.select-wrapper { position: relative; }
#categoryFilter {
    appearance: none; background: white; border: 1px solid #e2e8f0;
    padding: 10px 35px 10px 16px; border-radius: 12px; cursor: pointer; font-weight: 500;
}
.select-wrapper::after {
    content: "▼"; font-size: 0.6rem; position: absolute; right: 12px; top: 50%;
    transform: translateY(-50%); pointer-events: none; color: var(--primary);
}
.hero, .category-header { text-align: center; padding: 4rem 10%; animation: fadeIn 0.5s ease; }
.category-header { background: rgba(99, 102, 241, 0.05); border-bottom: 1px solid var(--border); }
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}
.back-btn {
    background: none; color: var(--primary); border: 1px solid var(--primary);
    padding: 8px 16px; border-radius: 8px; cursor: pointer; margin-bottom: 1rem;
}
#courseGrid {
    display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem; padding: 2rem 5%;
}
.course-card {
    background: var(--glass); backdrop-filter: blur(10px);
    border: 1px solid var(--border); border-radius: 24px; padding: 2rem;
}
.course-card:hover { transform: translateY(-10px); background: white; box-shadow: 0 20px 40px rgba(0,0,0,0.05); }
.category-tag {
    font-size: 0.7rem; font-weight: 700; color: var(--primary);
    background: #e0e7ff; padding: 4px 12px; border-radius: 20px;
}
.enroll-btn {
    width: 100%; padding: 12px; background: var(--primary);
    color: white; border: none; border-radius: 12px; font-weight: 600; cursor: pointer;
}
.modal { display: none; position: fixed; top: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.4); backdrop-filter: blur(6px); z-index: 1000; }
.modal-content { background: white; width: 400px; margin: 8% auto; padding: 2.5rem; border-radius: 28px; position: relative; box-shadow: 0 25px 50px -12px rgba(0,0,0,0.2); }
.modal-header { text-align: center; margin-bottom: 1.5rem; }
.modal-header h2 { margin: 0; font-size: 1.8rem; }
.modal-header p { color: #64748b; font-size: 0.9rem; margin: 5px 0 0 0; }
.close-btn { position: absolute; right: 20px; top: 20px; cursor: pointer; font-size: 1.2rem; color: #94a3b8; }
.input-group { margin-bottom: 1.2rem; }
.input-group label { display: block; font-size: 0.85rem; font-weight: 600; margin-bottom: 6px; color: #475569; }
.input-group input { width: 100%; padding: 12px; border-radius: 10px; border: 1.5px solid #e2e8f0; background: var(--input-bg); font-family: inherit; }
.input-group input:focus { outline: none; border-color: var(--primary); background: white; box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1); }
.enroll-confirm {
    width: 100%; padding: 14px; background: var(--primary); color: white; border: none;
    border-radius: 12px; font-weight: 700; cursor: pointer; margin-top: 10px;
}
.enroll-confirm:hover { transform: translateY(-2px); box-shadow: 0 10px 15px -3px rgba(99, 102, 241, 0.3); }