:root {
    --bg: #f4f6f8;
    --panel: #ffffff;
    --border: #dfe3e8;
    --text: #1f2933;
    --muted: #64748b;
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --danger: #dc2626;
    --success: #16a34a;
    --radius: 6px;
}

* { box-sizing: border-box; }

body {
    margin: 0;
    font-family: -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    font-size: 14px;
}

a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }

.layout { display: flex; min-height: 100vh; }

.sidebar {
    width: 230px;
    flex-shrink: 0;
    background: #111827;
    color: #e5e7eb;
    padding: 16px 0;
}

.sidebar h1 {
    font-size: 15px;
    padding: 0 16px 12px;
    margin: 0 0 8px;
    border-bottom: 1px solid #1f2937;
    color: #fff;
}

.sidebar .group-label {
    font-size: 10px;
    text-transform: uppercase;
    letter-spacing: .06em;
    color: #6b7280;
    padding: 12px 16px 4px;
}

.sidebar a {
    display: block;
    padding: 7px 16px;
    color: #cbd5e1;
    font-size: 13px;
}

.sidebar a:hover { background: #1f2937; text-decoration: none; }
.sidebar a.active { background: var(--primary); color: #fff; }

.main { flex: 1; padding: 24px 32px; max-width: 1200px; }

.topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.topbar .user { color: var(--muted); font-size: 13px; }

h2 { margin-top: 0; }

.panel {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 20px;
}

table { width: 100%; border-collapse: collapse; font-size: 13px; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
th { background: #f8fafc; font-weight: 600; color: var(--muted); text-transform: uppercase; font-size: 11px; letter-spacing: .04em; }
tr:hover td { background: #f9fafb; }

.form-row { margin-bottom: 14px; }
.form-row label { display: block; margin-bottom: 4px; font-weight: 600; font-size: 13px; }
.form-row .hint { color: var(--muted); font-size: 12px; margin-top: 3px; }

input[type=text], input[type=number], input[type=password], input[type=time], select, textarea {
    width: 100%;
    padding: 7px 10px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-size: 13px;
    background: #fff;
    color: var(--text);
}

textarea { min-height: 80px; }

.checkbox-row { display: flex; align-items: center; gap: 8px; }
.checkbox-row input { width: auto; }

.btn {
    display: inline-block;
    padding: 7px 16px;
    border-radius: var(--radius);
    border: 1px solid var(--primary);
    background: var(--primary);
    color: #fff;
    cursor: pointer;
    font-size: 13px;
}
.btn:hover { background: var(--primary-dark); text-decoration: none; }
.btn.secondary { background: #fff; color: var(--text); border-color: var(--border); }
.btn.secondary:hover { background: #f1f5f9; }
.btn.danger { background: #fff; color: var(--danger); border-color: var(--danger); }
.btn.danger:hover { background: #fef2f2; }
.btn.small { padding: 4px 10px; font-size: 12px; }

.alert { padding: 10px 14px; border-radius: var(--radius); margin-bottom: 16px; font-size: 13px; }
.alert.success { background: #f0fdf4; border: 1px solid #bbf7d0; color: #166534; }
.alert.error { background: #fef2f2; border: 1px solid #fecaca; color: #991b1b; }
.alert.info { background: #eff6ff; border: 1px solid #bfdbfe; color: #1e40af; }

.badge { display: inline-block; padding: 2px 8px; border-radius: 999px; font-size: 11px; background: #e5e7eb; color: #374151; }
.badge.lab { background: #fef3c7; color: #92400e; }

.actions-cell { white-space: nowrap; }
.actions-cell a, .actions-cell button { margin-right: 8px; }

.empty-state { color: var(--muted); padding: 24px; text-align: center; }

.two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }

.login-wrap { display: flex; align-items: center; justify-content: center; min-height: 100vh; }
.login-box { width: 340px; background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px; }

.disabled-card { opacity: .55; pointer-events: none; }

.tt-table { border-collapse: collapse; }
.tt-table th, .tt-table td { border: 1px solid var(--border); padding: 6px; text-align: center; font-size: 12px; vertical-align: top; min-width: 110px; }
.tt-cell-paper { font-weight: 600; }
.tt-cell-faculty { color: var(--muted); font-size: 11px; }
.tt-cell-room { color: #9333ea; font-size: 11px; }
.tt-empty { color: #cbd5e1; }
.tt-cell-class { color: #0f766e; font-size: 11px; font-weight: 600; }