/* Core Variables for Institutional Branding */
:root {
    --primary: #4f46e5;
    --primary-dark: #4338ca;
    --accent: #06b6d4;
    --danger: #ef4444;
    --success: #22c55e;
    --bg-main: #f8fafc;
    --sidebar-bg: #ffffff;
    --card-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-main);
    color: #1e293b;
}

/* Dashboard Layout */
.app-container {
    display: flex;
    height: 100vh;
    overflow: hidden;
}

/* Sidebar Custom Styling */
.sidebar {
    width: 260px;
    background: var(--sidebar-bg);
    border-right: 1px solid #e2e8f0;
    display: flex;
    flex-direction: column;
}

.nav-link {
    display: flex;
    align-items: center;
    padding: 12px 24px;
    color: #64748b;
    text-decoration: none;
    font-weight: 500;
    border-right: 4px solid transparent;
    transition: all 0.2s;
}

.nav-link.active {
    background: #f1f5f9;
    color: var(--primary);
    border-right-color: var(--primary);
}

/* Timetable Grid System */
.timetable-wrapper {
    background: white;
    border-radius: 12px;
    border: 1px solid #e2e8f0;
    overflow-x: auto;
}

.grid-header {
    display: grid;
    grid-template-columns: 100px repeat(5, 1fr);
    background: #1e293b;
    color: white;
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.grid-row {
    display: grid;
    grid-template-columns: 100px repeat(5, 1fr);
    border-bottom: 1px solid #f1f5f9;
}

.time-cell {
    padding: 20px;
    font-weight: 700;
    color: #94a3b8;
    text-align: center;
    border-right: 1px solid #f1f5f9;
}

.slot-cell {
    padding: 10px;
    min-height: 120px;
    border-right: 1px solid #f1f5f9;
}

/* Class Card Design */
.class-card {
    background: #eef2ff;
    border-left: 4px solid var(--primary);
    padding: 10px;
    border-radius: 8px;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

/* Modal Styling */
.modal-backdrop {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.5);
    backdrop-filter: blur(4px);
    display: none; /* Controlled by JS */
    justify-content: center;
    align-items: center;
    z-index: 1000;
}