/* =============================================
   THEME TRẮNG — Adaptive Learning System
   ============================================= */
:root {
    --primary:   #2563eb;   /* blue */
    --primary-light: #eff6ff;
    --accent:    #0ea5e9;
    --success:   #16a34a;
    --bg:        #f8fafc;
    --bg-card:   #ffffff;
    --border:    #e2e8f0;
    --text:      #1e293b;
    --text-muted:#64748b;
    --shadow:    0 1px 3px rgba(0,0,0,.08), 0 4px 12px rgba(0,0,0,.06);
    --shadow-lg: 0 4px 6px rgba(0,0,0,.05), 0 10px 25px rgba(0,0,0,.08);
    --radius:    12px;
    --radius-sm: 8px;
}

/* ── Body & layout ── */
body {
    background: var(--bg) !important;
    color: var(--text);
    min-height: 100vh;
    font-family: 'Inter', 'Segoe UI', system-ui, sans-serif;
}

/* ── Navbar (override dark) ── */
.navbar,
.navbar.navbar-dark.bg-dark,
nav.navbar {
    background: #ffffff !important;
    border-bottom: 1px solid var(--border) !important;
    box-shadow: 0 1px 4px rgba(0,0,0,.06) !important;
    padding: .6rem 1rem !important;
}
.navbar .navbar-brand,
.navbar .navbar-brand:hover {
    color: var(--primary) !important;
    font-weight: 700;
    font-size: 1.1rem;
}
.navbar .nav-link {
    color: var(--text-muted) !important;
    font-weight: 500;
    transition: color .15s;
}
.navbar .nav-link:hover,
.navbar .nav-link.active {
    color: var(--primary) !important;
}
.navbar .navbar-text,
.navbar .text-light,
.navbar .text-white {
    color: var(--text-muted) !important;
}
.navbar .navbar-toggler {
    border-color: var(--border) !important;
}
.navbar .navbar-toggler-icon {
    filter: invert(0) !important;
}
.navbar .btn-outline-light {
    color: var(--primary) !important;
    border-color: var(--primary) !important;
    background: transparent;
}
.navbar .btn-outline-light:hover {
    background: var(--primary) !important;
    color: #fff !important;
}

/* ── Cards ── */
.card {
    background: var(--bg-card) !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--radius) !important;
    box-shadow: var(--shadow) !important;
}
.card-header {
    background: var(--bg-card) !important;
    border-bottom: 1px solid var(--border) !important;
    color: var(--text) !important;
    font-weight: 600;
}
.card-header.bg-primary,
.card-header.bg-dark,
.card-header[style*="gradient"] {
    background: var(--primary-light) !important;
    color: var(--primary) !important;
    border-left: 3px solid var(--primary) !important;
}

/* Welcome / hero cards (home) */
.welcome-card {
    background: linear-gradient(135deg, var(--primary) 0%, #1d4ed8 100%) !important;
    color: #fff !important;
    border: none !important;
}
.welcome-card * { color: inherit !important; }

/* Content card (generic) */
.content-card {
    background: var(--bg-card) !important;
    border: 1px solid var(--border) !important;
    box-shadow: var(--shadow) !important;
}

/* ── Exam interface (thi_lam_bai / lam_bai) ── */
.exam-header {
    background: #ffffff !important;
    border-bottom: 2px solid var(--primary) !important;
    color: var(--text) !important;
    box-shadow: 0 2px 8px rgba(0,0,0,.06) !important;
}
.exam-header h5, .exam-header * { color: var(--text) !important; }
.timer {
    color: var(--primary) !important;
    background: var(--primary-light) !important;
    border: 1px solid #bfdbfe !important;
    border-radius: 8px;
    padding: .4rem .9rem;
    font-weight: 700;
}
.timer.warning { background: #fef9c3 !important; border-color: #fde047 !important; color: #92400e !important; }
.timer.danger  { background: #fee2e2 !important; border-color: #fca5a5 !important; color: #991b1b !important; }

/* Question cards */
.q-card, .question-card {
    background: #fff !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--radius) !important;
    box-shadow: var(--shadow) !important;
}
.q-nav {
    background: #fff !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--radius) !important;
}
.nav-btn { border: 1.5px solid var(--border) !important; background: #fff !important; }
.nav-btn.answered { background: #dbeafe !important; border-color: var(--primary) !important; }
.nav-btn.current  { background: var(--primary) !important; color: #fff !important; border-color: var(--primary) !important; }

/* Answer options */
.opt-label {
    border: 1.5px solid var(--border) !important;
    border-radius: var(--radius-sm) !important;
    background: #fff !important;
}
.opt-label:hover  { background: var(--primary-light) !important; border-color: var(--primary) !important; }
.opt-label.selected { background: #dbeafe !important; border-color: var(--primary) !important; }

/* ── Skill/practice cards ── */
.practice-card, .content-card {
    background: #fff !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--radius) !important;
    box-shadow: var(--shadow-lg) !important;
}
.skill-item {
    border: 1.5px solid var(--border) !important;
    border-radius: var(--radius-sm) !important;
    background: #fff !important;
    transition: all .15s;
}
.skill-item:hover {
    border-color: var(--primary) !important;
    background: var(--primary-light) !important;
    transform: translateX(4px);
}

/* ── Tables ── */
.table thead th {
    border-bottom: 2px solid var(--primary) !important;
    color: var(--primary) !important;
    background: var(--primary-light) !important;
    font-weight: 600;
}
.table-hover tbody tr:hover { background: var(--primary-light) !important; }

/* ── Buttons ── */
.btn-gradient,
.btn-primary {
    background: var(--primary) !important;
    border-color: var(--primary) !important;
    color: #fff !important;
}
.btn-gradient:hover, .btn-primary:hover {
    background: #1d4ed8 !important;
    border-color: #1d4ed8 !important;
}

/* ── Badges & status ── */
.exam-status.open   { background: #dcfce7 !important; color: #166534 !important; }
.exam-status.taken  { background: var(--primary-light) !important; color: #1e40af !important; }

/* ── Breadcrumb ── */
.breadcrumb { background: transparent !important; padding: 0 !important; }
.breadcrumb-item a { color: var(--primary) !important; }

/* ── Form elements ── */
.form-control:focus, .form-select:focus {
    border-color: var(--primary) !important;
    box-shadow: 0 0 0 .2rem rgba(37,99,235,.15) !important;
}

/* ── Misc overrides ── */
.border-primary { border-color: var(--primary) !important; }
.text-primary   { color: var(--primary) !important; }
.bg-primary     { background: var(--primary) !important; }

/* ── Page wrapper padding ── */
.container { padding-top: .5rem; }

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: #f1f5f9; }
::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 3px; }

/* ── Login page ── */
.login-card {
    border: 1px solid var(--border) !important;
    box-shadow: var(--shadow-lg) !important;
    border-radius: var(--radius) !important;
}
.login-container body {
    background: var(--bg) !important;
}

/* ── Flash alerts ── */
.alert { border-radius: var(--radius-sm) !important; }

/* ── Dropdown ── */
.dropdown-menu {
    border: 1px solid var(--border) !important;
    box-shadow: var(--shadow) !important;
    border-radius: var(--radius-sm) !important;
}
.dropdown-item:hover {
    background: var(--primary-light) !important;
    color: var(--primary) !important;
}

/* ── Page titles ── */
h1, h2, h3, h4, h5 { color: var(--text); }
.page-title {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text);
    border-left: 4px solid var(--primary);
    padding-left: .75rem;
    margin-bottom: 1.25rem;
}

/* ── Sidebar nav (teacher pages) ── */
.list-group-item-action:hover,
.list-group-item-action:focus {
    background: var(--primary-light) !important;
    color: var(--primary) !important;
}
.list-group-item.active {
    background: var(--primary) !important;
    border-color: var(--primary) !important;
}

/* ── Progress bars ── */
.progress-bar { background: var(--primary) !important; }