/* =============================================
   VTech Academy — Dark Tech / Industrial Theme
   Inspired by Linear, Vercel, ABB Robotics
   ============================================= */

:root {
    --bg-base: #0a0a1a;
    --bg-surface: #0f1225;
    --bg-card: #131830;
    --bg-card-hover: #181e3a;
    --bg-elevated: #1a2040;
    --bg-input: #0d1020;
    --border-color: rgba(99, 130, 255, 0.08);
    --border-accent: rgba(99, 130, 255, 0.15);
    --text-primary: #e2e8f0;
    --text-secondary: #8892b0;
    --text-muted: #5a6480;
    --accent-cyan: #06b6d4;
    --accent-blue: #3b82f6;
    --accent-violet: #8b5cf6;
    --accent-gradient: linear-gradient(135deg, #06b6d4, #8b5cf6);
    --accent-gradient-h: linear-gradient(90deg, #06b6d4, #3b82f6, #8b5cf6);
    --success: #22c55e;
    --warning: #f59e0b;
    --danger: #ef4444;
    --info: #06b6d4;
    --glow-cyan: 0 0 20px rgba(6, 182, 212, 0.15);
    --sidebar-width: 250px;
    --radius: 10px;
    --radius-lg: 14px;
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
}

/* === Base === */
html { font-size: 14px; }
@media (min-width: 768px) { html { font-size: 15px; } }

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background: var(--bg-base);
    color: var(--text-primary);
    font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
}

main { flex: 1; }

body::before {
    content: '';
    position: fixed;
    inset: 0;
    background-image:
        linear-gradient(rgba(99,130,255,0.03) 1px, transparent 1px),
        linear-gradient(90deg, rgba(99,130,255,0.03) 1px, transparent 1px);
    background-size: 60px 60px;
    pointer-events: none;
    z-index: -1;
}
::selection { background: rgba(6,182,212,0.3); color: #fff; }

::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg-base); }
::-webkit-scrollbar-thumb { background: rgba(99,130,255,0.15); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(99,130,255,0.3); }

a { color: var(--accent-cyan); text-decoration: none; transition: var(--transition); }
a:hover { color: #22d3ee; text-decoration: none; }

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

.sidebar {
    width: var(--sidebar-width);
    background: rgba(10,10,30,0.97);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 0; left: 0; bottom: 0;
    z-index: 1000;
    backdrop-filter: blur(20px);
    overflow-y: auto;
    overflow-x: hidden;
    transition: transform 0.3s ease;
}

.sidebar-brand {
    padding: 20px 20px 16px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 12px;
    text-decoration: none !important;
}
.sidebar-brand .brand-icon {
    width: 36px; height: 36px;
    background: var(--accent-gradient);
    border-radius: 10px;
    display: flex; align-items: center; justify-content: center;
    font-size: 18px; color: #fff; flex-shrink: 0;
}
.sidebar-brand .brand-text { font-size: 16px; font-weight: 700; color: #fff; letter-spacing: -0.3px; }
.sidebar-brand .brand-sub { font-size: 10px; color: var(--text-muted); text-transform: uppercase; letter-spacing: 1.5px; font-weight: 500; }

.sidebar-nav { padding: 12px 10px; flex: 1; }
.nav-section { font-size: 10px; text-transform: uppercase; letter-spacing: 1.5px; color: var(--text-muted); padding: 16px 12px 6px; font-weight: 600; }

.sidebar-link {
    display: flex; align-items: center; gap: 10px;
    padding: 9px 12px; border-radius: 8px;
    color: var(--text-secondary); font-size: 13.5px; font-weight: 500;
    transition: var(--transition); text-decoration: none !important;
    position: relative; margin: 1px 0;
}
.sidebar-link i { font-size: 16px; width: 20px; text-align: center; opacity: 0.7; transition: var(--transition); }
.sidebar-link:hover { background: rgba(99,130,255,0.08); color: var(--text-primary); }
.sidebar-link:hover i { opacity: 1; }
.sidebar-link.active { background: rgba(6,182,212,0.1); color: var(--accent-cyan); }
.sidebar-link.active::before {
    content: ''; position: absolute; left: 0; top: 6px; bottom: 6px; width: 3px;
    background: var(--accent-gradient); border-radius: 0 3px 3px 0;
}
.sidebar-link.active i { opacity: 1; color: var(--accent-cyan); }

.sidebar-user {
    padding: 14px 16px;
    border-top: 1px solid var(--border-color);
    display: flex; align-items: center; gap: 10px;
}
.sidebar-user .user-avatar {
    width: 34px; height: 34px; border-radius: 8px;
    background: var(--accent-gradient);
    display: flex; align-items: center; justify-content: center;
    font-size: 14px; font-weight: 700; color: #fff; flex-shrink: 0;
}
.sidebar-user .user-name { font-size: 13px; font-weight: 600; color: var(--text-primary); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.sidebar-user .user-role { font-size: 11px; color: var(--accent-cyan); font-weight: 500; }

.main-content { margin-left: var(--sidebar-width); flex: 1; min-height: 100vh; padding: 24px 32px; overflow-x: hidden; max-width: 100vw; box-sizing: border-box; }

.sidebar-toggle {
    display: none; position: fixed; top: 12px; left: 12px; z-index: 1001;
    background: var(--bg-card); border: 1px solid var(--border-color);
    color: var(--text-primary); padding: 8px 10px; border-radius: 8px; font-size: 18px; cursor: pointer;
}
.sidebar-overlay { display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.5); z-index: 999; }

@media (max-width: 991px) {
    .sidebar { transform: translateX(-100%); }
    .sidebar.show { transform: translateX(0); }
    .sidebar-toggle { display: block; }
    .sidebar-overlay.show { display: block; }
    .main-content { margin-left: 0; padding: 16px; padding-top: 56px; }
}

/* === Cards === */
.card {
    background: var(--bg-card); border: 1px solid var(--border-color);
    border-radius: var(--radius); color: var(--text-primary); transition: var(--transition);
}
.card:hover { border-color: var(--border-accent); }
.card-header { background: rgba(255,255,255,0.02) !important; border-bottom: 1px solid var(--border-color); color: var(--text-primary) !important; font-weight: 600; }
.card-footer { background: transparent !important; border-top: 1px solid var(--border-color); }

.stat-card {
    border-radius: var(--radius-lg); border: 1px solid var(--border-color) !important;
    box-shadow: var(--glow-cyan); transition: var(--transition);
    position: relative; overflow: hidden;
}
.stat-card::before { content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px; background: var(--accent-gradient); }
.stat-card:hover { transform: translateY(-3px); box-shadow: 0 8px 30px rgba(6,182,212,0.12); }
.stat-card .stat-icon { font-size: 2.5rem; opacity: 0.5; }
.stat-card .stat-number { font-size: 2rem; font-weight: 700; font-family: var(--font-mono); }

.stat-card.bg-primary { background: linear-gradient(135deg, rgba(59,130,246,0.15), rgba(59,130,246,0.05)) !important; border-color: rgba(59,130,246,0.2) !important; color: #93c5fd !important; }
.stat-card.bg-success { background: linear-gradient(135deg, rgba(34,197,94,0.15), rgba(34,197,94,0.05)) !important; border-color: rgba(34,197,94,0.2) !important; color: #86efac !important; }
.stat-card.bg-info { background: linear-gradient(135deg, rgba(6,182,212,0.15), rgba(6,182,212,0.05)) !important; border-color: rgba(6,182,212,0.2) !important; color: #67e8f9 !important; }
.stat-card.bg-warning { background: linear-gradient(135deg, rgba(245,158,11,0.15), rgba(245,158,11,0.05)) !important; border-color: rgba(245,158,11,0.2) !important; color: #fcd34d !important; }

/* === Tables === */
.table { color: var(--text-primary); --bs-table-bg: transparent; --bs-table-hover-bg: rgba(99,130,255,0.05); }
.table th { font-weight: 600; white-space: nowrap; color: var(--text-secondary); border-color: var(--border-color); font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.5px; }
.table td { border-color: var(--border-color); vertical-align: middle; }
.table-hover > tbody > tr:hover > * { --bs-table-bg-state: rgba(99,130,255,0.05); color: var(--text-primary); }
.table-light, thead.table-light { --bs-table-bg: rgba(99,130,255,0.04) !important; --bs-table-color: var(--text-secondary) !important; }

/* === Forms === */
.form-control, .form-select {
    background: var(--bg-input); border: 1px solid var(--border-color);
    color: var(--text-primary); border-radius: 8px; padding: 10px 14px; transition: var(--transition);
}
.form-control:focus, .form-select:focus {
    background: var(--bg-input); border-color: var(--accent-cyan);
    color: var(--text-primary); box-shadow: 0 0 0 3px rgba(6,182,212,0.1);
}
.form-control::placeholder { color: var(--text-muted); }
.form-label { color: var(--text-secondary); font-weight: 500; font-size: 0.9rem; margin-bottom: 6px; }
.form-check-input { background-color: var(--bg-input); border-color: var(--border-accent); }
.form-check-input:checked { background-color: var(--accent-cyan); border-color: var(--accent-cyan); }
.form-check-label { color: var(--text-primary); }
.form-text { color: var(--text-muted) !important; }
.input-group-text { background: var(--bg-card); border-color: var(--border-color); color: var(--text-secondary); }

/* === Buttons === */
.btn { border-radius: 8px; font-weight: 600; font-size: 0.9rem; padding: 8px 16px; transition: var(--transition); }
.btn-primary { background: var(--accent-gradient); border: none; color: #fff; box-shadow: 0 2px 10px rgba(6,182,212,0.2); }
.btn-primary:hover { background: linear-gradient(135deg, #22d3ee, #a78bfa); box-shadow: 0 4px 20px rgba(6,182,212,0.3); transform: translateY(-1px); }
.btn-success { background: var(--success); border-color: var(--success); }
.btn-success:hover { background: #16a34a; }
.btn-danger { background: var(--danger); border-color: var(--danger); }
.btn-warning { background: var(--warning); border-color: var(--warning); color: #000; }

.btn-outline-primary { color: var(--accent-cyan); border-color: rgba(6,182,212,0.3); }
.btn-outline-primary:hover { background: rgba(6,182,212,0.1); color: #22d3ee; border-color: var(--accent-cyan); }
.btn-outline-secondary { color: var(--text-secondary); border-color: var(--border-accent); }
.btn-outline-secondary:hover { background: rgba(99,130,255,0.08); color: var(--text-primary); border-color: rgba(99,130,255,0.2); }
.btn-outline-warning { color: var(--warning); border-color: rgba(245,158,11,0.3); }
.btn-outline-warning:hover { background: rgba(245,158,11,0.1); }
.btn-outline-danger { color: var(--danger); border-color: rgba(239,68,68,0.3); }
.btn-outline-danger:hover { background: rgba(239,68,68,0.1); }
.btn-outline-info { color: var(--info); border-color: rgba(6,182,212,0.3); }
.btn-outline-info:hover { background: rgba(6,182,212,0.1); }
.btn-outline-success { color: var(--success); border-color: rgba(34,197,94,0.3); }
.btn-outline-success:hover { background: rgba(34,197,94,0.1); }
.btn-outline-light { color: #e2e8f0; border-color: rgba(255,255,255,0.25); }
.btn-outline-light:hover { background: rgba(255,255,255,0.1); color: #fff; border-color: rgba(255,255,255,0.4); }

/* === Badges === */
.badge { font-weight: 600; padding: 5px 10px; border-radius: 6px; font-size: 0.78rem; letter-spacing: 0.3px; }
.badge.bg-primary { background: rgba(59,130,246,0.15) !important; color: #93c5fd !important; }
.badge.bg-secondary { background: rgba(100,116,139,0.2) !important; color: #94a3b8 !important; }
.badge.bg-success { background: rgba(34,197,94,0.15) !important; color: #86efac !important; }
.badge.bg-danger { background: rgba(239,68,68,0.15) !important; color: #fca5a5 !important; }
.badge.bg-warning { background: rgba(245,158,11,0.15) !important; color: #fcd34d !important; }
.badge.bg-info { background: rgba(6,182,212,0.15) !important; color: #67e8f9 !important; }
.badge.bg-dark { background: rgba(255,255,255,0.08) !important; color: var(--text-primary) !important; }

.badge-accepted { background: rgba(34,197,94,0.15); color: #86efac; }
.badge-wrong-answer { background: rgba(239,68,68,0.15); color: #fca5a5; }
.badge-compile-error { background: rgba(245,158,11,0.15); color: #fcd34d; }
.badge-runtime-error { background: rgba(249,115,22,0.15); color: #fdba74; }
.badge-tle { background: rgba(139,92,246,0.15); color: #c4b5fd; }
.badge-pending { background: rgba(100,116,139,0.15); color: #94a3b8; }
.badge-easy { background: rgba(34,197,94,0.15) !important; color: #86efac !important; }
.badge-medium { background: rgba(245,158,11,0.15) !important; color: #fcd34d !important; }
.badge-hard { background: rgba(239,68,68,0.15) !important; color: #fca5a5 !important; }

/* === Alerts === */
.alert { border-radius: var(--radius); border: 1px solid; }
.alert-success { background: rgba(34,197,94,0.08); border-color: rgba(34,197,94,0.2); color: #86efac; }
.alert-danger { background: rgba(239,68,68,0.08); border-color: rgba(239,68,68,0.2); color: #fca5a5; }
.alert-info { background: rgba(6,182,212,0.08); border-color: rgba(6,182,212,0.2); color: #67e8f9; }
.alert-warning { background: rgba(245,158,11,0.08); border-color: rgba(245,158,11,0.2); color: #fcd34d; }
.alert-light { background: rgba(255,255,255,0.03); border-color: var(--border-color); color: var(--text-primary); }
.alert-dismissible .btn-close { filter: invert(1) grayscale(100%) brightness(200%); }

/* === Lists === */
.list-group-item { background: transparent; border-color: var(--border-color); color: var(--text-primary); }
.list-group-item-action:hover { background: rgba(99,130,255,0.05); color: var(--text-primary); }
.list-group-item.active { background: rgba(6,182,212,0.1); border-color: rgba(6,182,212,0.2); color: var(--accent-cyan); }

/* === Progress === */
.progress { background: rgba(99,130,255,0.08); border-radius: 6px; height: 8px; overflow: hidden; }
.progress-bar { border-radius: 6px; }
.progress-bar.bg-success { background: var(--success) !important; }
.progress-bar.bg-warning { background: var(--warning) !important; }

/* === Dropdowns === */
.dropdown-menu { background: var(--bg-elevated); border: 1px solid var(--border-accent); border-radius: var(--radius); box-shadow: 0 8px 32px rgba(0,0,0,0.4); padding: 6px; }
.dropdown-item { color: var(--text-secondary); border-radius: 6px; padding: 8px 12px; font-size: 0.9rem; }
.dropdown-item:hover { background: rgba(99,130,255,0.08); color: var(--text-primary); }
.dropdown-divider { border-color: var(--border-color); }

/* === Modal === */
.modal-content { background: var(--bg-surface); border: 1px solid var(--border-accent); color: var(--text-primary); }
.modal-header { border-color: var(--border-color); }
.modal-footer { border-color: var(--border-color); }

/* === Editor === */
#editor-container { width: 100%; height: 450px; border: 1px solid var(--border-accent); border-radius: 8px; overflow: hidden; }

/* === Problem desc === */
.problem-description { background: var(--bg-card); border: 1px solid var(--border-color); border-radius: var(--radius); padding: 1.5rem; }

/* === Login === */
.login-container { max-width: 420px; margin: 0 auto; padding-top: 10vh; }
.login-container .card { background: rgba(19,24,48,0.9); border: 1px solid var(--border-accent); backdrop-filter: blur(20px); box-shadow: 0 20px 60px rgba(0,0,0,0.4), var(--glow-cyan); }
.login-container .card-body h3 { background: var(--accent-gradient-h); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.login-container .btn-primary { padding: 12px; font-size: 1rem; }

/* === Headings === */
h1, h2, h3, h4, h5, h6 { color: var(--text-primary); }

/* === Lab/Sim cards === */
.lab-card, .sim-card {
    border-radius: var(--radius-lg) !important; border: 1px solid var(--border-color) !important;
    background: var(--bg-card) !important; cursor: pointer; transition: var(--transition);
    position: relative; overflow: hidden;
}
.lab-card:hover, .sim-card:hover { transform: translateY(-4px); border-color: rgba(6,182,212,0.3) !important; box-shadow: 0 12px 40px rgba(6,182,212,0.08); }
.lab-icon { font-size: 2rem; background: var(--accent-gradient); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }

/* === Text overrides === */
.text-muted { color: var(--text-muted) !important; }
.text-primary { color: var(--accent-cyan) !important; }
.text-success { color: var(--success) !important; }
.text-danger { color: var(--danger) !important; }
.text-warning { color: var(--warning) !important; }
.text-info { color: var(--info) !important; }
.text-dark { color: var(--text-primary) !important; }
.text-white { color: #fff !important; }
.text-body { color: var(--text-primary) !important; }
.fw-bold, .fw-semibold, strong { color: var(--text-primary); }

/* === Background overrides === */
.bg-white, .bg-light { background: var(--bg-card) !important; }
.bg-dark { background: var(--bg-base) !important; }
.bg-primary.bg-opacity-10 { background: rgba(6,182,212,0.1) !important; }

/* === Border overrides === */
.border, .border-top, .border-bottom { border-color: var(--border-color) !important; }
.border-0 { border: none !important; }
.shadow-sm { box-shadow: 0 2px 12px rgba(0,0,0,0.2) !important; }
.shadow { box-shadow: 0 4px 20px rgba(0,0,0,0.3) !important; }

/* === Hide default navbar === */
.navbar { display: none !important; }

/* === Pagination === */
.page-link { background: var(--bg-card); border-color: var(--border-color); color: var(--text-secondary); }
.page-link:hover { background: rgba(99,130,255,0.08); color: var(--accent-cyan); border-color: var(--border-accent); }
.page-item.active .page-link { background: var(--accent-cyan); border-color: var(--accent-cyan); }

/* === Footer === */
footer { background: transparent !important; border-top: 1px solid var(--border-color) !important; color: var(--text-muted) !important; font-size: 0.85rem; }

/* === Nav pills/tabs === */
.nav-pills .nav-link { color: var(--text-secondary); border-radius: 8px; }
.nav-pills .nav-link.active { background: rgba(6,182,212,0.15); color: var(--accent-cyan); }
.nav-tabs { border-color: var(--border-color); }
.nav-tabs .nav-link { color: var(--text-secondary); }
.nav-tabs .nav-link.active { background: var(--bg-card); border-color: var(--border-color); border-bottom-color: var(--bg-card); color: var(--text-primary); }

/* === Accordion === */
.accordion-item { background: var(--bg-card); border-color: var(--border-color); }
.accordion-button { background: var(--bg-card); color: var(--text-primary); }
.accordion-button:not(.collapsed) { background: rgba(99,130,255,0.05); color: var(--accent-cyan); }

.vr { background: var(--border-accent) !important; opacity: 1 !important; }
hr { border-color: var(--border-color); opacity: 0.5; }
pre, code { color: var(--accent-cyan); background: rgba(6,182,212,0.08); padding: 2px 6px; border-radius: 4px; font-family: var(--font-mono); font-size: 0.9em; }
pre { padding: 16px; border-radius: var(--radius); border: 1px solid var(--border-color); }

/* === Problem Statement === */
.prob-body { font-size: 0.92rem; line-height: 1.75; color: var(--text-primary); }
.prob-body p { margin-bottom: 8px; }
.prob-body ul, .prob-body ol { padding-left: 20px; margin-bottom: 8px; }
.prob-body li { margin-bottom: 3px; }
.prob-body strong { color: var(--accent-cyan); font-weight: 600; }
.prob-body code {
    background: rgba(6,182,212,0.1); color: var(--accent-cyan);
    padding: 2px 7px; border-radius: 4px; font-size: 0.88em;
    font-family: var(--font-mono);
}
.prob-body pre {
    background: var(--bg-base); border: 1px solid var(--border-accent);
    border-radius: 8px; padding: 14px 16px; margin: 8px 0;
    font-family: var(--font-mono); font-size: 0.85rem;
    line-height: 1.5; overflow-x: auto; color: var(--text-primary);
}
.prob-body pre code { background: none; padding: 0; color: inherit; font-size: inherit; }
.prob-body blockquote {
    border-left: 3px solid var(--accent-violet);
    padding: 8px 14px; margin: 10px 0;
    background: rgba(139,92,246,0.06); border-radius: 0 6px 6px 0;
    color: var(--text-secondary); font-size: 0.88rem;
}
.prob-note {
    background: rgba(245,158,11,0.08); border: 1px solid rgba(245,158,11,0.2);
    border-radius: 8px; padding: 10px 14px; margin: 12px 0;
    font-size: 0.88rem; color: #fcd34d;
    display: flex; gap: 8px; align-items: flex-start;
}
.prob-note i { font-size: 1rem; margin-top: 2px; flex-shrink: 0; }
.prob-note p { margin-bottom: 4px; }
[data-theme="light"] .prob-body strong { color: var(--accent-cyan); }
[data-theme="light"] .prob-body code { background: rgba(8,145,178,0.08); color: #0e7490; }
[data-theme="light"] .prob-body pre { background: #f8f9fc; border-color: var(--border-color); color: var(--text-primary); }
[data-theme="light"] .prob-body pre code { color: inherit; }
[data-theme="light"] .prob-note { background: rgba(217,119,6,0.06); color: #92400e; }

/* === Animations === */
@keyframes fadeInUp { from { opacity: 0; transform: translateY(16px); } to { opacity: 1; transform: translateY(0); } }
@keyframes pulse-glow { 0%,100% { box-shadow: 0 0 10px rgba(6,182,212,0.1); } 50% { box-shadow: 0 0 20px rgba(6,182,212,0.25); } }

.stat-card, .lab-card, .card { animation: fadeInUp 0.4s ease-out both; }
.row > [class*="col-"]:nth-child(1) > .card { animation-delay: 0s; }
.row > [class*="col-"]:nth-child(2) > .card { animation-delay: 0.05s; }
.row > [class*="col-"]:nth-child(3) > .card { animation-delay: 0.1s; }
.row > [class*="col-"]:nth-child(4) > .card { animation-delay: 0.15s; }

.score-text { font-size: 0.85rem; font-weight: 600; font-family: var(--font-mono); }
.online-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--success); display: inline-block; animation: pulse-glow 2s infinite; box-shadow: 0 0 8px rgba(34,197,94,0.4); }

/* === Breadcrumb === */
.breadcrumb-item a { color: var(--accent-cyan); }
.breadcrumb-item.active { color: var(--text-muted); }
.breadcrumb-item + .breadcrumb-item::before { color: var(--text-muted); }

/* === Sidebar Settings Bar === */
.sidebar-settings {
    display: flex; align-items: center; justify-content: center; gap: 6px;
    padding: 8px 16px;
    border-top: 1px solid var(--border-color);
}
.setting-btn {
    width: 34px; height: 34px; border-radius: 8px;
    background: rgba(99,130,255,0.06); border: 1px solid var(--border-color);
    color: var(--text-secondary); display: flex; align-items: center; justify-content: center;
    cursor: pointer; transition: var(--transition); font-size: 14px;
}
.setting-btn:hover { background: rgba(6,182,212,0.12); color: var(--accent-cyan); border-color: rgba(6,182,212,0.3); }

/* =============================================
   Light Theme
   ============================================= */
[data-theme="light"] {
    --bg-base: #f4f6fb;
    --bg-surface: #ffffff;
    --bg-card: #ffffff;
    --bg-card-hover: #f0f2f8;
    --bg-elevated: #f8f9fc;
    --bg-input: #ffffff;
    --border-color: rgba(0,0,0,0.08);
    --border-accent: rgba(0,0,0,0.12);
    --text-primary: #1a1a2e;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --accent-cyan: #0891b2;
    --accent-blue: #2563eb;
    --accent-violet: #7c3aed;
    --accent-gradient: linear-gradient(135deg, #0891b2, #7c3aed);
    --accent-gradient-h: linear-gradient(90deg, #0891b2, #2563eb, #7c3aed);
    --success: #16a34a;
    --warning: #d97706;
    --danger: #dc2626;
    --info: #0891b2;
    --glow-cyan: 0 2px 12px rgba(8,145,178,0.08);
}

[data-theme="light"] body { background: var(--bg-base); color: var(--text-primary); }
[data-theme="light"] body::before { background-image: none; }

[data-theme="light"] .sidebar { background: rgba(255,255,255,0.97); border-right-color: var(--border-color); }
[data-theme="light"] .sidebar-brand .brand-text { color: var(--text-primary); }
[data-theme="light"] .sidebar-link { color: var(--text-secondary); }
[data-theme="light"] .sidebar-link:hover { background: rgba(0,0,0,0.04); color: var(--text-primary); }
[data-theme="light"] .sidebar-link.active { background: rgba(8,145,178,0.08); color: var(--accent-cyan); }
[data-theme="light"] .sidebar-user .user-name { color: var(--text-primary); }

[data-theme="light"] .card { background: var(--bg-card); border-color: var(--border-color); color: var(--text-primary); box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
[data-theme="light"] .card-header { background: rgba(0,0,0,0.02) !important; color: var(--text-primary) !important; border-color: var(--border-color); }

[data-theme="light"] .stat-card.bg-primary { background: linear-gradient(135deg, rgba(37,99,235,0.08), rgba(37,99,235,0.02)) !important; color: #1e40af !important; }
[data-theme="light"] .stat-card.bg-success { background: linear-gradient(135deg, rgba(22,163,74,0.08), rgba(22,163,74,0.02)) !important; color: #15803d !important; }
[data-theme="light"] .stat-card.bg-info { background: linear-gradient(135deg, rgba(8,145,178,0.08), rgba(8,145,178,0.02)) !important; color: #0e7490 !important; }
[data-theme="light"] .stat-card.bg-warning { background: linear-gradient(135deg, rgba(217,119,6,0.08), rgba(217,119,6,0.02)) !important; color: #92400e !important; }

[data-theme="light"] .table { color: var(--text-primary); }
[data-theme="light"] .table th { color: var(--text-secondary); }
[data-theme="light"] .table-light, [data-theme="light"] thead.table-light { --bs-table-bg: rgba(0,0,0,0.02) !important; --bs-table-color: var(--text-secondary) !important; }

[data-theme="light"] .form-control, [data-theme="light"] .form-select { background: #fff; border-color: var(--border-color); color: var(--text-primary); }
[data-theme="light"] .form-control:focus, [data-theme="light"] .form-select:focus { border-color: var(--accent-cyan); background: #fff; }

[data-theme="light"] .dropdown-menu { background: #fff; border-color: var(--border-color); box-shadow: 0 8px 24px rgba(0,0,0,0.1); }
[data-theme="light"] .dropdown-item { color: var(--text-secondary); }
[data-theme="light"] .dropdown-item:hover { background: rgba(0,0,0,0.04); color: var(--text-primary); }

[data-theme="light"] .modal-content { background: #fff; border-color: var(--border-color); color: var(--text-primary); }

[data-theme="light"] .list-group-item { color: var(--text-primary); border-color: var(--border-color); }
[data-theme="light"] .list-group-item-action:hover { background: rgba(0,0,0,0.03); }

[data-theme="light"] .alert-dismissible .btn-close { filter: none; }
[data-theme="light"] .alert-success { background: rgba(22,163,74,0.06); border-color: rgba(22,163,74,0.15); color: #15803d; }
[data-theme="light"] .alert-danger { background: rgba(220,38,38,0.06); border-color: rgba(220,38,38,0.15); color: #991b1b; }
[data-theme="light"] .alert-info { background: rgba(8,145,178,0.06); border-color: rgba(8,145,178,0.15); color: #0e7490; }
[data-theme="light"] .alert-warning { background: rgba(217,119,6,0.06); border-color: rgba(217,119,6,0.15); color: #92400e; }
[data-theme="light"] .alert-light { background: rgba(0,0,0,0.02); border-color: var(--border-color); color: var(--text-primary); }

[data-theme="light"] .badge.bg-primary { background: rgba(37,99,235,0.1) !important; color: #1e40af !important; }
[data-theme="light"] .badge.bg-secondary { background: rgba(100,116,139,0.1) !important; color: #475569 !important; }
[data-theme="light"] .badge.bg-success { background: rgba(22,163,74,0.1) !important; color: #15803d !important; }
[data-theme="light"] .badge.bg-danger { background: rgba(220,38,38,0.1) !important; color: #991b1b !important; }
[data-theme="light"] .badge.bg-warning { background: rgba(217,119,6,0.1) !important; color: #92400e !important; }
[data-theme="light"] .badge.bg-info { background: rgba(8,145,178,0.1) !important; color: #0e7490 !important; }

[data-theme="light"] .badge-accepted { background: rgba(22,163,74,0.1); color: #15803d; }
[data-theme="light"] .badge-wrong-answer { background: rgba(220,38,38,0.1); color: #991b1b; }
[data-theme="light"] .badge-compile-error { background: rgba(217,119,6,0.1); color: #92400e; }
[data-theme="light"] .badge-runtime-error { background: rgba(234,88,12,0.1); color: #9a3412; }
[data-theme="light"] .badge-tle { background: rgba(124,58,237,0.1); color: #6d28d9; }
[data-theme="light"] .badge-pending { background: rgba(100,116,139,0.1); color: #475569; }

[data-theme="light"] .text-muted { color: var(--text-muted) !important; }
[data-theme="light"] .text-dark { color: var(--text-primary) !important; }
[data-theme="light"] .fw-bold, [data-theme="light"] .fw-semibold, [data-theme="light"] strong { color: inherit; }
[data-theme="light"] h1, [data-theme="light"] h2, [data-theme="light"] h3, [data-theme="light"] h4, [data-theme="light"] h5, [data-theme="light"] h6 { color: var(--text-primary); }

[data-theme="light"] .bg-white, [data-theme="light"] .bg-light { background: #fff !important; }
[data-theme="light"] .shadow-sm { box-shadow: 0 1px 3px rgba(0,0,0,0.06) !important; }
[data-theme="light"] .shadow { box-shadow: 0 4px 12px rgba(0,0,0,0.08) !important; }

[data-theme="light"] pre, [data-theme="light"] code { background: rgba(8,145,178,0.06); color: #0e7490; }
[data-theme="light"] .progress { background: rgba(0,0,0,0.06); }

[data-theme="light"] .page-link { background: #fff; border-color: var(--border-color); color: var(--text-secondary); }
[data-theme="light"] .page-link:hover { background: rgba(0,0,0,0.03); }

[data-theme="light"] footer { border-top-color: var(--border-color) !important; color: var(--text-muted) !important; }

[data-theme="light"] .setting-btn { background: rgba(0,0,0,0.04); border-color: var(--border-color); color: var(--text-secondary); }
[data-theme="light"] .setting-btn:hover { background: rgba(8,145,178,0.08); color: var(--accent-cyan); }

[data-theme="light"] .sidebar-toggle { background: #fff; border-color: var(--border-color); color: var(--text-primary); }
[data-theme="light"] .lab-card, [data-theme="light"] .sim-card { background: #fff !important; border-color: var(--border-color) !important; }
[data-theme="light"] .lab-card:hover, [data-theme="light"] .sim-card:hover { border-color: rgba(8,145,178,0.3) !important; box-shadow: 0 8px 24px rgba(8,145,178,0.06); }

[data-theme="light"] ::-webkit-scrollbar-track { background: var(--bg-base); }
[data-theme="light"] ::-webkit-scrollbar-thumb { background: rgba(0,0,0,0.12); }
[data-theme="light"] ::-webkit-scrollbar-thumb:hover { background: rgba(0,0,0,0.2); }

[data-theme="light"] .login-container .card { background: rgba(255,255,255,0.95); box-shadow: 0 20px 60px rgba(0,0,0,0.08); }

[data-theme="light"] .nav-section { color: var(--text-muted); }
[data-theme="light"] .vr { background: var(--border-color) !important; }
[data-theme="light"] hr { border-color: var(--border-color); }
[data-theme="light"] a { color: var(--accent-cyan); }
[data-theme="light"] a:hover { color: #0e7490; }
[data-theme="light"] ::selection { background: rgba(8,145,178,0.2); color: #000; }

/* === Mobile Responsive === */
@media (max-width: 768px) {
    .main-content { padding: 12px 12px !important; }
    h1, h2 { font-size: 1.3rem; }
    h3 { font-size: 1.1rem; }
    .table { font-size: 0.82rem; }
    .btn-sm { padding: 4px 8px; font-size: 0.75rem; }
    .card-body { padding: 12px; }
}

@media (max-width: 576px) {
    .main-content { padding: 8px 8px !important; }
    h1, h2 { font-size: 1.15rem; }
    .badge { font-size: 0.65rem; padding: 2px 5px; }
    .btn { font-size: 0.8rem; padding: 6px 10px; }
    .btn-sm { padding: 3px 6px; font-size: 0.72rem; min-height: 32px; }
}