:root {
    --bg-dark: #0f0f16;
    --glass-bg: rgba(30, 30, 45, 0.6);
    --glass-border: rgba(255, 255, 255, 0.1);
    --primary: #4F46E5;
    --primary-hover: #4338ca;
    --text-main: #f8f9fa;
    --text-muted: #9ca3af;
    --danger: #ef4444;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Inter', sans-serif;
}

body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    min-height: 100vh;
}

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

.screen {
    width: 100vw;
    height: 100vh;
    display: flex;
}

.hidden {
    display: none !important;
}

/* Auth Screen */
#auth-screen {
    align-items: center;
    justify-content: center;
}

.auth-box {
    padding: 2rem;
    width: 100%;
    max-width: 400px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    text-align: center;
}

input, select {
    width: 100%;
    padding: 0.75rem 1rem;
    background: rgba(0,0,0,0.2);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    color: white;
    font-size: 1rem;
}

input:focus, select:focus {
    outline: none;
    border-color: var(--primary);
}

button {
    background: var(--primary);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}

button:hover {
    background: var(--primary-hover);
}

button.secondary {
    background: transparent;
    border: 1px solid var(--glass-border);
}

button.secondary:hover {
    background: rgba(255,255,255,0.05);
}

.error-msg {
    color: var(--danger);
    font-size: 0.875rem;
}

/* Dashboard Layout */
.sidebar {
    width: 260px;
    height: 100vh;
    border-radius: 0;
    border-top: none;
    border-bottom: none;
    border-left: none;
    display: flex;
    flex-direction: column;
}

.sidebar-header {
    padding: 1.5rem;
    border-bottom: 1px solid var(--glass-border);
}

nav {
    flex: 1;
    padding: 1rem 0;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.nav-btn {
    background: transparent;
    text-align: left;
    padding: 1rem 1.5rem;
    border-radius: 0;
    font-weight: 500;
    color: var(--text-muted);
}

.nav-btn:hover {
    background: rgba(255,255,255,0.05);
}

.nav-btn.active {
    background: rgba(79, 70, 229, 0.15);
    color: var(--primary);
    border-right: 3px solid var(--primary);
}

.sidebar-footer {
    padding: 1.5rem;
    border-top: 1px solid var(--glass-border);
}

.sidebar-footer button {
    width: 100%;
    background: rgba(255,255,255,0.05);
}

.content {
    flex: 1;
    overflow-y: auto;
    padding: 2rem;
}

.view {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.header-action {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Tables */
.table-container {
    overflow-x: auto;
    border-radius: 12px;
}

table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
}

th, td {
    padding: 1rem;
    border-bottom: 1px solid var(--glass-border);
}

th {
    background: rgba(0,0,0,0.2);
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    font-size: 0.75rem;
    letter-spacing: 0.05em;
}

tr:last-child td {
    border-bottom: none;
}

.badge {
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
}

.badge.staff { background: rgba(79, 70, 229, 0.2); color: #818cf8; }
.badge.student { background: rgba(16, 185, 129, 0.2); color: #34d399; }

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

.batch-card {
    padding: 1.5rem;
    cursor: pointer;
    transition: transform 0.2s, background 0.2s;
}

.batch-card:hover {
    transform: translateY(-2px);
    background: rgba(255,255,255,0.08);
}

.batch-card h3 {
    margin-bottom: 0.5rem;
}

.batch-card p {
    color: var(--text-muted);
    font-size: 0.875rem;
}

/* Modals & Overlays */
.modal, .overlay {
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.7);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 100;
}

.modal-content {
    padding: 2rem;
    width: 100%;
    max-width: 400px;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
    margin-top: 1rem;
}

.overlay-content {
    width: 90%;
    height: 90%;
    display: flex;
    flex-direction: column;
    padding: 2rem;
}

.overlay-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}