:root {
    /* Light Mode Variables */
    --bg-color: #f4f7f6;
    --text-color: #333;
    --primary-color: #4f46e5;
    --secondary-color: #818cf8;
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(255, 255, 255, 0.5);
    --card-shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.1);
}

[data-theme="dark"] {
    /* Dark Mode Variables */
    --bg-color: #0f172a;
    --text-color: #f1f5f9;
    --primary-color: #6366f1;
    --secondary-color: #818cf8;
    --glass-bg: rgba(30, 41, 59, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
    --card-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    transition: background-color 0.3s, color 0.3s;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Glassmorphism Utility */
.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
}

/* Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 5%;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--card-shadow);
}

.logo h2 { color: var(--primary-color); }
.logo span { color: var(--text-color); }
.subtitle { font-size: 0.8rem; opacity: 0.8; }

.search-container {
    position: relative;
    width: 40%;
}

.search-container input {
    width: 100%;
    padding: 0.8rem 1rem 0.8rem 2.5rem;
    border-radius: 20px;
    border: 1px solid var(--glass-border);
    background: var(--glass-bg);
    color: var(--text-color);
    outline: none;
}

.search-container i {
    position: absolute;
    left: 15px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-color);
    opacity: 0.6;
}

.icon-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-color);
    cursor: pointer;
}

/* Layout */
.container {
    flex: 1;
    padding: 2rem 5%;
}

.class-selector {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    justify-content: center;
}

.class-btn {
    padding: 0.8rem 2rem;
    border-radius: 30px;
    border: 1px solid var(--primary-color);
    background: transparent;
    color: var(--text-color);
    cursor: pointer;
    font-weight: bold;
}

.class-btn.active, .class-btn:hover {
    background: var(--primary-color);
    color: white;
}

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

.card {
    border-radius: 15px;
    padding: 1.5rem;
    box-shadow: var(--card-shadow);
    display: flex;
    flex-direction: column;
    gap: 1rem;
    transform: translateY(0);
    transition: transform 0.3s;
}

.card:hover {
    transform: translateY(-5px);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

.meta-info {
    font-size: 0.8rem;
    opacity: 0.7;
    margin-top: 0.5rem;
}

.btn-group {
    display: flex;
    gap: 0.5rem;
    margin-top: auto;
}

.btn {
    flex: 1;
    padding: 0.6rem;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    text-align: center;
    text-decoration: none;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-secondary {
    background: transparent;
    border: 1px solid var(--primary-color);
    color: var(--text-color);
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.6);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal-content {
    width: 80%;
    max-width: 900px;
    padding: 2rem;
    border-radius: 15px;
    position: relative;
}

.close-btn {
    position: absolute;
    top: 15px; right: 20px;
    font-size: 1.5rem;
    cursor: pointer;
}

.iframe-container {
    margin-top: 1rem;
    border-radius: 10px;
    overflow: hidden;
}

/* WhatsApp Float */
.whatsapp-float {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background-color: #25d366;
    color: #FFF;
    border-radius: 50px;
    width: 60px;
    height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 30px;
    box-shadow: 2px 2px 10px rgba(0,0,0,0.2);
    z-index: 100;
}

/* Footer */
footer {
    padding: 1.5rem 5%;
    text-align: center;
    margin-top: auto;
}
.footer-links { margin-top: 0.5rem; }
.footer-links a { color: var(--primary-color); text-decoration: none; margin: 0 0.5rem; }

/* Responsive */
@media (max-width: 768px) {
    .navbar { flex-direction: column; gap: 1rem; }
    .search-container { width: 100%; }
    .modal-content { width: 95%; padding: 1rem; }
}