/* ========== CSS VARIABLES ========== */
:root {
    --bg: #f0f2f5; --surface: #ffffff; --surface2: #f8f9fb;
    --border: #e2e8f0; --border2: #cbd5e1;
    --primary: #6366f1; --primary-light: #818cf8; --primary-dark: #4f46e5;
    --primary-bg: rgba(99,102,241,0.08); --primary-glow: rgba(99,102,241,0.25);
    --accent: #0891b2; --accent-bg: rgba(8,145,178,0.08);
    --text: #1e293b; --text2: #64748b; --text3: #94a3b8;
    --success: #10b981; --success-bg: rgba(16,185,129,0.1);
    --warning: #f59e0b; --warning-bg: rgba(245,158,11,0.1);
    --danger: #ef4444; --danger-bg: rgba(239,68,68,0.1);
    --info: #3b82f6; --info-bg: rgba(59,130,246,0.1);
    --sidebar-w: 260px; --radius: 10px; --radius-lg: 14px;
    --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-lg: 0 4px 16px rgba(0,0,0,0.08);
    --font: 'DM Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    --mono: 'JetBrains Mono', monospace;
}

[data-theme="dark"] {
    --bg: #0b0f19; --surface: #131a2b; --surface2: #1a2332;
    --border: #243044; --border2: #2d3f56;
    --text: #e8ecf4; --text2: #8899ab; --text3: #5a6b80;
    --shadow: 0 1px 3px rgba(0,0,0,0.3); --shadow-lg: 0 4px 16px rgba(0,0,0,0.4);
    --primary-bg: rgba(99,102,241,0.12);
}

/* ========== RESET ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 15px; }
body { font-family: var(--font); background: var(--bg); color: var(--text); line-height: 1.6; min-height: 100vh; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; }
table { border-collapse: collapse; width: 100%; }

/* ========== APP LAYOUT ========== */
.app-layout { display: flex; min-height: 100vh; }

/* ========== SIDEBAR ========== */
.sidebar {
    width: var(--sidebar-w); background: var(--surface); border-right: 1px solid var(--border);
    display: flex; flex-direction: column; position: fixed; top: 0; left: 0; bottom: 0; z-index: 100;
    transition: transform 0.3s ease;
}
.sidebar-header {
    padding: 1.25rem 1.25rem 0.75rem; display: flex; align-items: center; justify-content: space-between;
}
.sidebar-logo { display: flex; align-items: center; gap: 0.6rem; }
.logo-icon { font-size: 1.5rem; background: var(--primary); color: #fff; width: 36px; height: 36px; border-radius: 8px; display: flex; align-items: center; justify-content: center; }
.logo-text { font-size: 1.15rem; font-weight: 700; color: var(--text); }
.logo-text span { color: var(--primary); }
.sidebar-close { display: none; background: none; border: none; font-size: 1.5rem; color: var(--text2); cursor: pointer; }

.sidebar-user {
    display: flex; align-items: center; gap: 0.75rem; padding: 1rem 1.25rem;
    margin: 0.5rem 0.75rem; background: var(--surface2); border-radius: var(--radius);
}
.user-avatar {
    width: 40px; height: 40px; border-radius: 10px; background: linear-gradient(135deg, var(--primary), var(--accent));
    color: #fff; display: flex; align-items: center; justify-content: center; font-weight: 700; font-size: 1rem; flex-shrink: 0;
}
.user-info { overflow: hidden; }
.user-name { font-weight: 600; font-size: 0.9rem; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.user-role { font-size: 0.75rem; color: var(--text2); text-transform: uppercase; letter-spacing: 0.5px; }

.sidebar-nav { padding: 0.5rem 0.75rem; flex: 1; overflow-y: auto; }
.nav-item {
    display: flex; align-items: center; gap: 0.75rem; padding: 0.65rem 1rem; border-radius: var(--radius);
    color: var(--text2); font-size: 0.9rem; font-weight: 500; text-decoration: none; transition: all 0.15s;
    margin-bottom: 2px;
}
.nav-item:hover { background: var(--primary-bg); color: var(--primary); text-decoration: none; }
.nav-item.active { background: var(--primary-bg); color: var(--primary); font-weight: 600; }
.nav-icon { font-size: 1.1rem; width: 24px; text-align: center; }
.nav-divider { height: 1px; background: var(--border); margin: 0.75rem 0; }
.nav-logout { color: var(--danger); }
.nav-logout:hover { background: var(--danger-bg); color: var(--danger); }

/* ========== MAIN CONTENT ========== */
.main-content { margin-left: var(--sidebar-w); flex: 1; display: flex; flex-direction: column; min-height: 100vh; }
.top-bar {
    display: flex; align-items: center; gap: 1rem; padding: 1rem 1.75rem;
    background: var(--surface); border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 50;
}
.menu-toggle { display: none; background: none; border: none; font-size: 1.3rem; color: var(--text); cursor: pointer; }
.page-title { font-size: 1.2rem; font-weight: 700; flex: 1; }
.top-bar-actions { display: flex; align-items: center; gap: 1rem; }
.notif-bell { position: relative; cursor: pointer; font-size: 1.25rem; }
.notif-badge {
    position: absolute; top: -6px; right: -8px; background: var(--danger); color: #fff;
    font-size: 0.65rem; font-weight: 700; padding: 1px 5px; border-radius: 50px; min-width: 16px; text-align: center;
}

.content-area { padding: 1.5rem 1.75rem; flex: 1; }

/* ========== CARDS ========== */
.card {
    background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
    padding: 1.5rem; box-shadow: var(--shadow); margin-bottom: 1.25rem;
}
.card-header {
    display: flex; align-items: center; justify-content: space-between; margin-bottom: 1rem;
    padding-bottom: 0.75rem; border-bottom: 1px solid var(--border);
}
.card-title { font-size: 1.05rem; font-weight: 700; }

/* ========== STAT CARDS ========== */
.stats-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 1rem; margin-bottom: 1.5rem; }
.stat-card {
    background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
    padding: 1.25rem 1.5rem; box-shadow: var(--shadow); position: relative; overflow: hidden;
}
.stat-card::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
}
.stat-card.purple::before { background: var(--primary); }
.stat-card.cyan::before { background: var(--accent); }
.stat-card.green::before { background: var(--success); }
.stat-card.orange::before { background: var(--warning); }
.stat-card.red::before { background: var(--danger); }
.stat-card.blue::before { background: var(--info); }
.stat-value { font-size: 2rem; font-weight: 700; line-height: 1.2; }
.stat-label { font-size: 0.85rem; color: var(--text2); margin-top: 0.25rem; }

/* ========== TABLES ========== */
.table-wrapper { overflow-x: auto; }
.data-table { width: 100%; font-size: 0.9rem; }
.data-table th {
    text-align: left; padding: 0.75rem 1rem; background: var(--surface2); font-weight: 600;
    color: var(--text2); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.5px;
    border-bottom: 1px solid var(--border);
}
.data-table td { padding: 0.75rem 1rem; border-bottom: 1px solid var(--border); vertical-align: middle; }
.data-table tbody tr:hover { background: var(--primary-bg); }

/* ========== BADGES ========== */
.badge {
    display: inline-flex; padding: 0.2rem 0.65rem; border-radius: 50px; font-size: 0.75rem;
    font-weight: 600; text-transform: uppercase; letter-spacing: 0.3px;
}
.badge-primary { background: var(--primary-bg); color: var(--primary); }
.badge-success { background: var(--success-bg); color: var(--success); }
.badge-warning { background: var(--warning-bg); color: var(--warning); }
.badge-danger { background: var(--danger-bg); color: var(--danger); }
.badge-info { background: var(--info-bg); color: var(--info); }

/* ========== FORMS ========== */
.form-group { margin-bottom: 1.15rem; }
.form-label { display: block; font-size: 0.85rem; font-weight: 600; color: var(--text2); margin-bottom: 0.35rem; }
.form-control {
    width: 100%; padding: 0.7rem 0.9rem; background: var(--surface2); border: 1px solid var(--border);
    border-radius: var(--radius); color: var(--text); font-family: var(--font); font-size: 0.9rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}
.form-control:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-glow); }
select.form-control { appearance: none; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%2364748b' d='M6 8L1 3h10z'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 0.75rem center; padding-right: 2rem; }
textarea.form-control { resize: vertical; min-height: 80px; }
.form-row { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.form-check { display: flex; align-items: center; gap: 0.5rem; }
.form-check input[type="checkbox"] { width: 18px; height: 18px; accent-color: var(--primary); }
.form-hint { font-size: 0.8rem; color: var(--text3); margin-top: 0.25rem; }

/* ========== BUTTONS ========== */
.btn {
    display: inline-flex; align-items: center; gap: 0.4rem; padding: 0.65rem 1.25rem;
    border-radius: var(--radius); font-family: var(--font); font-size: 0.9rem; font-weight: 600;
    cursor: pointer; border: 1px solid transparent; transition: all 0.15s; text-decoration: none;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); color: #fff; }
.btn-success { background: var(--success); color: #fff; }
.btn-danger { background: var(--danger); color: #fff; }
.btn-outline { background: transparent; border-color: var(--border); color: var(--text2); }
.btn-outline:hover { border-color: var(--primary); color: var(--primary); }
.btn-sm { padding: 0.4rem 0.8rem; font-size: 0.8rem; }
.btn-lg { padding: 0.85rem 1.75rem; font-size: 1rem; }
.btn-block { display: flex; justify-content: center; width: 100%; }
.btn-group { display: flex; gap: 0.5rem; flex-wrap: wrap; }

/* ========== ALERTS ========== */
.alert {
    padding: 0.85rem 1.15rem; border-radius: var(--radius); margin-bottom: 1rem; font-size: 0.9rem;
    border: 1px solid; display: flex; align-items: center; gap: 0.5rem;
}
.alert-success { background: var(--success-bg); border-color: rgba(16,185,129,0.3); color: var(--success); }
.alert-danger, .alert-error { background: var(--danger-bg); border-color: rgba(239,68,68,0.3); color: var(--danger); }
.alert-warning { background: var(--warning-bg); border-color: rgba(245,158,11,0.3); color: var(--warning); }
.alert-info { background: var(--info-bg); border-color: rgba(59,130,246,0.3); color: var(--info); }

/* ========== MODAL ========== */
.modal-overlay {
    position: fixed; inset: 0; background: rgba(0,0,0,0.5); backdrop-filter: blur(4px);
    display: none; align-items: center; justify-content: center; z-index: 1000; padding: 1rem;
}
.modal-overlay.active { display: flex; }
.modal {
    background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
    width: 100%; max-width: 540px; max-height: 90vh; overflow-y: auto; padding: 1.75rem;
}
.modal-title { font-size: 1.2rem; font-weight: 700; margin-bottom: 1.25rem; }
.modal-actions { display: flex; gap: 0.75rem; justify-content: flex-end; margin-top: 1.5rem; }

/* ========== EXAM TAKING UI ========== */
.exam-header {
    display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 1rem;
    padding: 1rem 1.5rem; background: var(--surface); border: 1px solid var(--border);
    border-radius: var(--radius-lg); margin-bottom: 1.25rem;
}
.exam-timer {
    font-family: var(--mono); font-size: 1.5rem; font-weight: 700; color: var(--primary);
    padding: 0.5rem 1.25rem; background: var(--primary-bg); border-radius: var(--radius);
}
.exam-timer.danger { color: var(--danger); background: var(--danger-bg); animation: pulse 1s infinite; }

@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.6; } }

.question-nav {
    display: flex; flex-wrap: wrap; gap: 0.4rem; margin-bottom: 1.25rem;
    padding: 1rem; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
}
.q-nav-btn {
    width: 38px; height: 38px; border-radius: 8px; display: flex; align-items: center; justify-content: center;
    font-size: 0.85rem; font-weight: 600; cursor: pointer; border: 1px solid var(--border);
    background: var(--surface2); color: var(--text2); transition: all 0.15s;
}
.q-nav-btn:hover { border-color: var(--primary); color: var(--primary); }
.q-nav-btn.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.q-nav-btn.answered { background: var(--success); color: #fff; border-color: var(--success); }

.question-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg); padding: 1.75rem; margin-bottom: 1.25rem; }
.question-number { font-size: 0.8rem; font-weight: 600; color: var(--primary); text-transform: uppercase; letter-spacing: 0.5px; margin-bottom: 0.5rem; }
.question-text { font-size: 1.1rem; font-weight: 600; margin-bottom: 1.25rem; line-height: 1.5; }
.option-list { display: flex; flex-direction: column; gap: 0.6rem; }
.option-item {
    display: flex; align-items: center; gap: 0.75rem; padding: 0.85rem 1.15rem;
    background: var(--surface2); border: 2px solid var(--border); border-radius: var(--radius);
    cursor: pointer; transition: all 0.15s; font-size: 0.95rem;
}
.option-item:hover { border-color: var(--primary-light); background: var(--primary-bg); }
.option-item.selected { border-color: var(--primary); background: var(--primary-bg); }
.option-radio {
    width: 20px; height: 20px; border-radius: 50%; border: 2px solid var(--border2); flex-shrink: 0;
    display: flex; align-items: center; justify-content: center; transition: all 0.15s;
}
.option-item.selected .option-radio { border-color: var(--primary); background: var(--primary); }
.option-item.selected .option-radio::after { content: ''; width: 8px; height: 8px; border-radius: 50%; background: #fff; }

.exam-actions { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 0.75rem; }

/* ========== AUTH PAGES ========== */
.auth-layout {
    min-height: 100vh; display: flex; align-items: center; justify-content: center; padding: 2rem;
    background: var(--bg);
    background-image: radial-gradient(ellipse at 20% 50%, rgba(99,102,241,0.06) 0%, transparent 50%),
                      radial-gradient(ellipse at 80% 50%, rgba(8,145,178,0.04) 0%, transparent 50%);
}
.auth-card {
    width: 100%; max-width: 440px; background: var(--surface); border: 1px solid var(--border);
    border-radius: 16px; padding: 2.5rem; box-shadow: var(--shadow-lg); position: relative; overflow: hidden;
}
.auth-card::before {
    content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--accent));
}

/* ========== EMPTY STATE ========== */
.empty-state {
    text-align: center; padding: 3rem 1rem; color: var(--text2);
}
.empty-state-icon { font-size: 3rem; margin-bottom: 0.75rem; opacity: 0.5; }
.empty-state h3 { font-size: 1.1rem; margin-bottom: 0.5rem; color: var(--text); }

/* ========== LEADERBOARD ========== */
.leaderboard-rank {
    width: 32px; height: 32px; border-radius: 50%; display: flex; align-items: center; justify-content: center;
    font-weight: 700; font-size: 0.85rem;
}
.rank-1 { background: linear-gradient(135deg, #fbbf24, #f59e0b); color: #fff; }
.rank-2 { background: linear-gradient(135deg, #9ca3af, #6b7280); color: #fff; }
.rank-3 { background: linear-gradient(135deg, #d97706, #b45309); color: #fff; }

/* ========== ANTI-CHEAT OVERLAY ========== */
.cheat-warning {
    position: fixed; inset: 0; background: rgba(0,0,0,0.9); display: none; align-items: center;
    justify-content: center; z-index: 9999; color: #fff; text-align: center;
}
.cheat-warning.active { display: flex; }
.cheat-warning h2 { font-size: 1.5rem; margin-bottom: 0.5rem; color: var(--danger); }
.cheat-warning p { color: var(--text3); }

/* ========== PROGRESS BAR ========== */
.progress-bar { height: 8px; background: var(--surface2); border-radius: 50px; overflow: hidden; }
.progress-fill { height: 100%; background: linear-gradient(90deg, var(--primary), var(--accent)); border-radius: 50px; transition: width 0.3s; }

/* ========== RESPONSIVE ========== */
@media (max-width: 768px) {
    .sidebar { transform: translateX(-100%); }
    .sidebar.open { transform: translateX(0); }
    .sidebar-close { display: block; }
    .main-content { margin-left: 0; }
    .menu-toggle { display: block; }
    .stats-grid { grid-template-columns: 1fr 1fr; }
    .form-row { grid-template-columns: 1fr; }
    .content-area { padding: 1rem; }
    .exam-header { flex-direction: column; align-items: stretch; text-align: center; }
}

@media (max-width: 480px) {
    .stats-grid { grid-template-columns: 1fr; }
    .auth-card { padding: 1.5rem; }
}

/* ========== LANDING PAGE ========== */
.landing-hero {
    min-height: 100vh; display: flex; flex-direction: column; align-items: center;
    justify-content: center; text-align: center; padding: 2rem;
    background: var(--bg);
    background-image: radial-gradient(ellipse at 30% 20%, rgba(99,102,241,0.1) 0%, transparent 50%),
                      radial-gradient(ellipse at 70% 80%, rgba(8,145,178,0.08) 0%, transparent 50%);
}
.landing-logo { font-size: 3rem; font-weight: 700; margin-bottom: 0.5rem; }
.landing-logo span { color: var(--primary); }
.landing-tagline { font-size: 1.25rem; color: var(--text2); margin-bottom: 2rem; max-width: 500px; }
.landing-actions { display: flex; gap: 1rem; flex-wrap: wrap; justify-content: center; }
.landing-features {
    display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 1.5rem; max-width: 900px; margin-top: 3rem;
}
.feature-card {
    background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-lg);
    padding: 1.5rem; text-align: left; box-shadow: var(--shadow);
}
.feature-icon { font-size: 2rem; margin-bottom: 0.75rem; }
.feature-card h3 { font-size: 1rem; margin-bottom: 0.4rem; }
.feature-card p { font-size: 0.85rem; color: var(--text2); }