:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --danger: #dc2626;
    --warning: #d97706;
    --success: #16a34a;
    --bg: #f3f4f6;
    --card-bg: #ffffff;
    --border: #e5e7eb;
    --text: #111827;
    --muted: #6b7280;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); line-height: 1.5; }
h1, h2, h3 { margin-top: 0; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
.muted { color: var(--muted); }
.small { font-size: 0.875rem; }

/* ---------- Layout ---------- */
.container { max-width: 1100px; margin: 0 auto; padding: 24px 16px 64px; }

.topnav {
    display: flex;
    align-items: center;
    gap: 24px;
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    padding: 14px 24px;
}
.topnav-brand { font-weight: 700; font-size: 1.1rem; display: flex; align-items: center; gap: 10px; }
.topnav-links { display: flex; gap: 18px; flex: 1; }
.topnav-links a { color: var(--text); font-weight: 500; }
.topnav-user { display: flex; align-items: center; gap: 12px; color: var(--muted); }

/* ---------- Cards ---------- */
.card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 20px 24px;
    margin: 20px 0;
}

.stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 14px; margin: 20px 0; }
.stat-card { background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 18px; text-align: center; }
.stat-number { font-size: 2rem; font-weight: 700; color: var(--primary); }
.stat-label { color: var(--muted); font-size: 0.875rem; margin-top: 4px; }

.quick-actions { display: flex; gap: 12px; margin: 20px 0; flex-wrap: wrap; }

/* ---------- Forms ---------- */
label { display: block; font-weight: 600; margin: 14px 0 6px; font-size: 0.9rem; }
input[type=text], input[type=password], input[type=number], input[type=email],
input[type=datetime-local], select, textarea {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    background: #fff;
}
textarea { resize: vertical; font-family: inherit; }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
.checkbox-row { display: flex; gap: 24px; margin: 16px 0; }
.checkbox-row label, .checkbox-grid label { font-weight: 400; display: flex; align-items: center; gap: 8px; }
.checkbox-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 10px; margin: 14px 0; }

.select-all-row { display: flex; align-items: center; gap: 8px; font-weight: 400; cursor: pointer; }
.select-all-global { padding: 10px 0; border-bottom: 2px solid var(--border); margin-bottom: 6px; }
.class-group { margin: 18px 0; padding-top: 10px; border-top: 1px solid var(--border); }
.select-all-class { padding: 4px 0 8px; }
.class-checkbox-grid { margin-left: 24px; margin-top: 4px; }
.class-heading-row { background: #f3f4f6; font-weight: 700; }
.class-filter-row { display: flex; align-items: center; gap: 10px; margin-bottom: 14px; }
.class-filter-row select { width: auto; padding: 6px 10px; }

/* ---------- School branding ---------- */
.brand-logo { height: 32px; width: auto; max-width: 140px; object-fit: contain; }
.brand-logo-dark { filter: brightness(0) invert(1); } /* renders logo white on dark exam header bar */
.brand-block { text-align: center; margin-bottom: 8px; }
.brand-logo-large { height: 64px; width: auto; max-width: 260px; object-fit: contain; margin-bottom: 10px; }
.exam-header-brand { display: flex; align-items: center; gap: 10px; font-weight: 600; }
.logo-preview-box { padding: 16px; background: #f9fafb; border: 1px solid var(--border); border-radius: 8px; display: inline-block; margin-bottom: 10px; }
.logo-preview-box .logo-preview-img { height: 60px; width: auto; max-width: 240px; object-fit: contain; display: block; }
.download-btn-group { display: inline-flex; gap: 8px; margin-right: 8px; }
.download-btn-group .btn { margin-top: 0; }

.btn {
    display: inline-block;
    padding: 10px 20px;
    border-radius: 8px;
    border: none;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 16px;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-secondary { background: #fff; color: var(--text); border: 1px solid var(--border); }
.btn-link { color: var(--primary); font-weight: 500; background: none; border: none; cursor: pointer; padding: 0; font-size: 0.9rem; }
.btn-link-danger { color: var(--danger); }

/* ---------- Alerts ---------- */
.alert { padding: 12px 16px; border-radius: 8px; margin: 16px 0; font-size: 0.95rem; }
.alert-success { background: #dcfce7; color: #166534; }
.alert-error { background: #fee2e2; color: #991b1b; }
.alert-warning { background: #fef3c7; color: #92400e; }

/* ---------- Tables ---------- */
.data-table { width: 100%; border-collapse: collapse; margin-top: 12px; }
.data-table th, .data-table td { text-align: left; padding: 10px 12px; border-bottom: 1px solid var(--border); font-size: 0.9rem; }
.data-table th { color: var(--muted); font-weight: 600; }
.highlight-row { background: #eff6ff; }

.badge { display: inline-block; padding: 2px 10px; border-radius: 999px; font-size: 0.75rem; font-weight: 600; }
.badge-scheduled { background: #dbeafe; color: #1e40af; }
.badge-active { background: #dcfce7; color: #166534; }
.badge-completed { background: #e5e7eb; color: #374151; }
.badge-cancelled { background: #fee2e2; color: #991b1b; }
.badge-draft { background: #f3f4f6; color: #6b7280; }
.badge-easy { background: #dcfce7; color: #166534; }
.badge-medium { background: #fef3c7; color: #92400e; }
.badge-hard { background: #fee2e2; color: #991b1b; }
.badge-in_progress { background: #dbeafe; color: #1e40af; }
.badge-submitted { background: #dcfce7; color: #166534; }
.badge-auto_submitted { background: #fef3c7; color: #92400e; }
.badge-terminated { background: #fee2e2; color: #991b1b; }

/* ---------- Question preview ---------- */
.question-preview { border-bottom: 1px solid var(--border); padding: 16px 0; }
.question-preview:last-child { border-bottom: none; }
.question-preview-header { font-weight: 500; margin-bottom: 8px; display: flex; align-items: center; gap: 10px; }
.option-list { list-style: none; padding: 0; margin: 8px 0; }
.option-list li { padding: 6px 10px; border-radius: 6px; margin-bottom: 4px; background: #f9fafb; }
.correct-option { background: #dcfce7 !important; font-weight: 600; }
.wrong-option { background: #fee2e2 !important; }
.selected-option { border: 2px solid var(--primary); }

/* ---------- Auth pages ---------- */
.auth-page { display: flex; align-items: center; justify-content: center; min-height: 100vh; padding: 20px; }
.auth-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 36px 32px;
    max-width: 420px;
    width: 100%;
    box-shadow: 0 4px 24px rgba(0,0,0,0.08);
}
.result-score { font-size: 2.5rem; font-weight: 800; color: var(--primary); text-align: center; margin: 20px 0; }

/* ---------- Exam-taking page ---------- */
.exam-page { margin: 0; background: #fff; user-select: none; }
.exam-header {
    position: sticky; top: 0; z-index: 10;
    display: flex; align-items: center; justify-content: space-between;
    padding: 14px 24px; background: var(--text); color: #fff;
}
.exam-timer { font-size: 1.3rem; font-weight: 700; font-variant-numeric: tabular-nums; }
.exam-timer.timer-critical { color: #fca5a5; animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: 0.5; } }
.violation-indicator { background: var(--danger); padding: 4px 12px; border-radius: 999px; font-size: 0.85rem; }
.exam-header-btn { margin: 0; padding: 8px 16px; font-size: 0.85rem; }
.exam-header-right { display: flex; align-items: center; gap: 16px; }

.palette-bar {
    display: flex; flex-wrap: wrap; gap: 6px;
    padding: 12px 24px; background: #f9fafb; border-bottom: 1px solid var(--border);
    position: sticky; top: 57px; z-index: 9;
}
.palette-bar-large { padding: 12px 0; position: static; background: none; border: none; }
.palette-btn {
    width: 36px; height: 36px;
    border: 1px solid var(--border); border-radius: 6px; background: #fff;
    cursor: pointer; font-weight: 600; font-size: 0.85rem; color: var(--text);
}
.palette-btn:hover { background: #f3f4f6; }
.palette-btn.palette-current { border-color: var(--primary); border-width: 2px; }
.palette-btn.palette-answered { background: #dcfce7; border-color: #16a34a; color: #166534; }
.palette-btn.palette-unanswered { background: #fef3c7; border-color: #d97706; color: #92400e; }

.exam-question-nav { display: flex; justify-content: space-between; gap: 10px; margin-top: 24px; }
.exam-question-nav .btn { margin-top: 0; }
.exam-question-nav .nav-prev-btn { margin-right: auto; }

.review-screen { padding: 20px 0; }
.review-screen h2 { margin-bottom: 6px; }
#submitExamBtn { margin-top: 20px; }

.exam-body { max-width: 800px; margin: 0 auto; padding: 24px 16px 100px; }
.exam-question { padding: 20px 0; border-bottom: 1px solid var(--border); }
.exam-question-number { color: var(--muted); font-size: 0.85rem; margin-bottom: 6px; }
.exam-question-text { font-size: 1.15rem; font-weight: 600; margin-bottom: 14px; }
.exam-options { display: flex; flex-direction: column; gap: 10px; }
.exam-option {
    display: flex; align-items: center; gap: 10px;
    padding: 12px 16px; border: 1px solid var(--border); border-radius: 8px;
    cursor: pointer;
}
.exam-option:hover { background: #f9fafb; }
.exam-option input { width: auto; margin: 0; }

.exam-footer {
    position: fixed; bottom: 0; left: 0; right: 0;
    background: #fff; border-top: 1px solid var(--border);
    padding: 14px 24px; text-align: center;
}

.fullscreen-overlay {
    position: fixed; inset: 0; background: rgba(17,24,39,0.95);
    display: flex; align-items: center; justify-content: center; z-index: 100;
}
.fullscreen-overlay-box { background: #fff; border-radius: 12px; padding: 32px; max-width: 420px; text-align: center; }

/* ---------- PDF upload box ---------- */
.pdf-upload-box {
    background: #f9fafb;
    border: 1px dashed var(--border);
    border-radius: 8px;
    padding: 14px 16px;
    margin: 8px 0 14px;
}
.pdf-upload-label { margin: 0 0 8px; font-size: 0.85rem; }
.pdf-upload-row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.pdf-upload-row input[type=file] { flex: 1; min-width: 200px; padding: 6px; border: 1px solid var(--border); border-radius: 6px; background: #fff; }
.pdf-upload-row .btn { margin-top: 0; white-space: nowrap; }
.extract-success { color: var(--success); }
.extract-error { color: var(--danger); }