/* ===== ROOT VARIABLES ===== */
:root {
    --bg: #f1f5f9;
    --primary: #3b82f6;
    --primary-dark: #2563eb;
    --primary-light: rgba(59, 130, 246, 0.1);
    --muted: #64748b;
    --card: #ffffff;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --radius: 12px;
    --radius-sm: 8px;
    --gap: 16px;
    --max-width: 1200px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

    /* z-index layers for modals */
    --z-overlay-attendance: 1000;
    --z-modal-attendance: 1100;
    --z-overlay-instructor: 1200;
    --z-modal-instructor: 1300;

    --transition: 0.2s ease;
}

* {
    box-sizing: border-box;
}

html,
body {
    height: 100%;
    margin: 0;
    font-family: var(--font-sans);
    background: var(--bg);
    color: #0f172a;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* ===== Topbar ===== */
.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 14px 24px;
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    color: #fff;
    box-shadow: var(--shadow);
}

.topbar h1 {
    margin: 0;
    font-size: 1.15rem;
    font-weight: 600;
    letter-spacing: -0.01em;
}

.topbar .btn-ghost {
    background: rgba(255, 255, 255, 0.1);
    color: #fff;
    border: 1px solid rgba(255, 255, 255, 0.2);
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.topbar .btn-ghost:hover {
    background: rgba(255, 255, 255, 0.2);
}

/* ===== Main Layout ===== */
.main {
    margin: 0 auto;
    display: grid;
    grid-template-columns: 260px 1fr;
    min-height: calc(100vh - 60px);
}

/* ===== Sidebar ===== */
.sidebar {
    background: var(--card);
    border-radius: var(--radius);
    padding: 20px 16px;
    box-shadow: var(--shadow);
    height: fit-content;
    position: sticky;
    top: 16px;
}

.sidebar ul {
    padding: 0;
    margin: 0;
    list-style: none;
}

.sidebar li {
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    color: #475569;
    margin-bottom: 4px;
    transition: var(--transition);
    font-weight: 500;
    font-size: 14px;
}

.sidebar li.active {
    background: var(--primary);
    color: #fff;
    font-weight: 600;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.35);
}

.sidebar li:hover:not(.active) {
    background: var(--primary-light);
    color: var(--primary);
}

/* ===== Content ===== */
.content {
    background: var(--card);
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    min-height: 60vh;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition);
    font-size: 14px;
}

.btn:hover {
    transform: translateY(-1px);
}

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

.btn-primary:hover {
    background: var(--primary-dark);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.35);
}

.btn-success {
    background: var(--success);
    color: #fff;
}

.btn-success:hover {
    background: #059669;
}

.btn-danger {
    background: var(--danger);
    color: #fff;
}

.btn-danger:hover {
    background: #dc2626;
}

.btn-ghost {
    background: transparent;
    color: var(--muted);
    border: 1px solid #e2e8f0;
}

.btn-ghost:hover {
    background: #f8fafc;
    border-color: var(--primary);
    color: var(--primary);
}

/* ===== Small Buttons ===== */
.btn-sm {
    padding: 6px 12px;
    font-size: 12px;
    border-radius: 6px;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    font-weight: 600;
}

/* ===== Tables ===== */
.details-table,
.bookings-table {
    width: 100%;
    border-collapse: collapse;
}

.details-table th,
.details-table td,
.bookings-table th,
.bookings-table td {
    padding: 14px 16px;
    text-align: left;
    border-bottom: 1px solid #f1f5f9;
}

.details-table th,
.bookings-table th {
    background-color: #f8fafc;
    font-weight: 600;
    color: #475569;
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.details-table td,
.bookings-table td {
    background: #fff;
}

.details-table tbody tr:hover,
.bookings-table tbody tr:hover {
    background: #f8fafc;
}

/* ===== Error & Empty ===== */
.error {
    padding: 16px;
    background: #fef2f2;
    color: #dc2626;
    border-radius: var(--radius-sm);
    margin-bottom: 12px;
    font-weight: 500;
}

.empty {
    padding: 48px 16px;
    background: #f8fafc;
    color: #64748b;
    border-radius: var(--radius-sm);
    text-align: center;
}

/* ==========================================================
   ATTENDANCE MODAL
   ========================================================== */
.attendance-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    z-index: var(--z-overlay-attendance);
    transition: all 0.3s ease;
}

.attendance-overlay.active {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.attendance-modal {
    position: fixed;
    top: 50%;
    left: 50%;
    width: 440px;
    max-height: 85vh;
    overflow-y: auto;
    background: var(--card);
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    transform: translate(-50%, -40%);
    opacity: 0;
    pointer-events: none;
    z-index: var(--z-modal-attendance);
    transition: all 0.3s ease;
}

.attendance-modal.active {
    transform: translate(-50%, -50%);
    opacity: 1;
    pointer-events: auto;
}

.attendance-modal h3 {
    margin: 0 0 20px;
    font-size: 1.25rem;
    font-weight: 700;
    text-align: center;
    color: #0f172a;
}

.attendance-modal table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: 20px;
}

.attendance-modal th,
.attendance-modal td {
    padding: 12px;
    border-bottom: 1px solid #f1f5f9;
    text-align: center;
}

.attendance-modal th {
    background: #f8fafc;
    font-weight: 600;
    font-size: 12px;
    text-transform: uppercase;
    color: #475569;
    position: sticky;
    top: 0;
    z-index: 10;
}

.attendance-modal input[type="checkbox"] {
    transform: scale(1.3);
    cursor: pointer;
}

#saveAttendanceBtn {
    background: var(--primary);
    color: #fff;
    font-weight: 600;
    padding: 12px 20px;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

#saveAttendanceBtn:hover {
    background: var(--primary-dark);
}

#closeAttendanceBtn {
    background: #f1f5f9;
    color: #475569;
    padding: 12px 20px;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    margin-left: 8px;
    font-weight: 500;
    transition: var(--transition);
}

#closeAttendanceBtn:hover {
    background: #e2e8f0;
}

/* ==========================================================
   INSTRUCTOR MODAL
   ========================================================== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    z-index: var(--z-overlay-instructor);
    transition: 0.3s;
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
}

.modal {
    position: fixed;
    top: 50%;
    left: 50%;
    background: var(--card);
    padding: 24px;
    border-radius: var(--radius);
    width: 440px;
    box-shadow: var(--shadow-lg);
    transform: translate(-50%, -40%);
    opacity: 0;
    pointer-events: none;
    z-index: var(--z-modal-instructor);
    transition: 0.3s;
}

.modal.active {
    transform: translate(-50%, -50%);
    opacity: 1;
    pointer-events: auto;
}

.attendance-counter {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.attendance-counter button {
    width: 32px;
    height: 32px;
    border: none;
    border-radius: var(--radius-sm);
    background: var(--primary);
    color: #fff;
    font-weight: 700;
    font-size: 16px;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.attendance-counter button:hover {
    background: var(--primary-dark);
}

.attendance-counter span {
    min-width: 28px;
    text-align: center;
    font-weight: 600;
    font-size: 15px;
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {
    .main {
        grid-template-columns: 1fr;
        padding: 16px;
    }

    .sidebar {
        display: none;
    }
}

@media (max-width: 480px) {
    body {
        font-size: 14px;
    }

    .attendance-modal,
    .modal {
        width: 95%;
        padding: 20px;
    }

    .details-table th,
    .details-table td,
    .bookings-table th,
    .bookings-table td {
        padding: 10px 12px;
        font-size: 13px;
    }

    .btn {
        padding: 10px 14px;
        font-size: 13px;
    }

    .topbar {
        padding: 12px 16px;
    }

    .topbar h1 {
        font-size: 1rem;
    }
}