/* ==========================================================================
   MODERN UI, DESIGN SYSTEM & DARK MODE FOR TRACNGHIEMTINHOC
   ========================================================================== */

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --primary-light: rgba(37, 99, 235, 0.1);
    --accent-color: #f59e0b;
    --success-color: #10b981;
    --danger-color: #ef4444;
    --bg-color: #f8fafc;
    --card-bg: #ffffff;
    --text-color: #1e293b;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    --nav-bg: rgba(255, 255, 255, 0.95);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
    --shadow-soft: 0 10px 25px -5px rgba(0, 0, 0, 0.05), 0 8px 10px -6px rgba(0, 0, 0, 0.01);
    --shadow-hover: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

/* =========================================
   DARK THEME VARIABLES
   ========================================= */
:root[data-theme="dark"],
html[data-theme="dark"],
body[data-theme="dark"],
html.dark-theme,
body.dark-theme {
    --primary-color: #60a5fa;
    --primary-hover: #93c5fd;
    --primary-light: rgba(96, 165, 250, 0.15);
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --text-color: #f8fafc;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --nav-bg: rgba(15, 23, 42, 0.95);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.4);
    --shadow-soft: 0 10px 25px -5px rgba(0, 0, 0, 0.5);
    --shadow-hover: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif !important;
    transition: background-color 0.25s ease, color 0.25s ease;
}

[data-theme="dark"] body,
body.dark-theme,
html.dark-theme body {
    background-color: var(--bg-color) !important;
    color: var(--text-color) !important;
}

/* =========================================
   COMPACT SINGLE-ROW NAVBAR STYLING
   ========================================= */
.navbar-default {
    background: var(--nav-bg) !important;
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: none !important;
    border-bottom: 1px solid var(--border-color) !important;
    box-shadow: var(--shadow-sm);
    min-height: 50px !important;
    height: 50px;
    padding: 0 !important;
    margin-bottom: 0 !important;
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: background-color 0.25s ease, border-color 0.25s ease;
}

@media (min-width: 768px) {
    /* Đảm bảo chiều rộng container lọt giữa 2 Wing Ads (tối đa 1040px, cách mép tối thiểu 180-200px) */
    .navbar-default .container {
        max-width: 1040px !important;
        width: 100% !important;
        height: 50px !important;
        display: flex !important;
        align-items: center !important;
        justify-content: space-between !important;
        padding-left: 12px !important;
        padding-right: 12px !important;
        margin: 0 auto !important;
    }

    .navbar-default .navbar-header {
        float: none !important;
        display: flex !important;
        align-items: center !important;
        margin: 0 !important;
        flex-shrink: 0;
    }

    .navbar-default .navbar-brand {
        float: none !important;
        height: auto !important;
        padding: 0 14px 0 0 !important;
        font-weight: 700 !important;
        color: var(--primary-color) !important;
        font-size: 15px !important;
        display: inline-flex !important;
        align-items: center !important;
        white-space: nowrap !important;
    }

    .navbar-default .navbar-collapse.collapse {
        display: flex !important;
        align-items: center !important;
        justify-content: space-between !important;
        flex: 1 1 auto !important;
        height: 50px !important;
        padding: 0 !important;
        margin: 0 !important;
        border: none !important;
        box-shadow: none !important;
        overflow: visible !important;
    }

    .navbar-default .navbar-nav {
        display: flex !important;
        flex-direction: row !important;
        align-items: center !important;
        float: none !important;
        margin: 0 !important;
        gap: 2px !important;
    }

    .navbar-default .navbar-nav > li {
        float: none !important;
        display: inline-flex !important;
        align-items: center !important;
    }

    .navbar-default .navbar-nav > li > a {
        color: var(--text-color) !important;
        font-weight: 500 !important;
        font-size: 13px !important;
        padding: 6px 8px !important;
        border-radius: 6px !important;
        line-height: 1.4 !important;
        white-space: nowrap !important;
        display: inline-flex !important;
        align-items: center !important;
        gap: 4px !important;
        transition: all 0.2s ease !important;
    }

    .navbar-default .navbar-nav > li > a:hover,
    .navbar-default .navbar-nav > li > a:focus {
        color: var(--primary-color) !important;
        background-color: var(--primary-light) !important;
    }

    .navbar-default .navbar-nav > .active > a,
    .navbar-default .navbar-nav > .active > a:hover,
    .navbar-default .navbar-nav > .active > a:focus {
        color: var(--primary-color) !important;
        background-color: var(--primary-light) !important;
        font-weight: 700 !important;
    }

    /* Nhóm nút bên phải: Theme toggle, Language, Login */
    .navbar-default .navbar-nav.navbar-right {
        display: flex !important;
        align-items: center !important;
        float: none !important;
        margin: 0 !important;
        gap: 6px !important;
        flex-shrink: 0;
    }

    .navbar-default .navbar-nav.navbar-right > li {
        float: none !important;
        display: inline-flex !important;
        align-items: center !important;
    }
}

/* Nút Đăng nhập dạng Badge / Pill trên Navbar */
.nav-login-btn {
    background: linear-gradient(135deg, var(--primary-color) 0%, #1d4ed8 100%) !important;
    color: #ffffff !important;
    font-weight: 600 !important;
    font-size: 12.5px !important;
    padding: 5px 14px !important;
    border-radius: 20px !important;
    box-shadow: 0 2px 6px rgba(37, 99, 235, 0.3) !important;
    text-decoration: none !important;
    transition: all 0.2s ease !important;
    display: inline-flex !important;
    align-items: center !important;
    white-space: nowrap !important;
}

.nav-login-btn:hover {
    transform: translateY(-1px) !important;
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.4) !important;
    color: #ffffff !important;
}

/* Nút Theme Toggle tinh tế */
.theme-toggle-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    color: var(--text-color);
    cursor: pointer;
    font-size: 13.5px;
    transition: all 0.25s ease;
    box-shadow: var(--shadow-sm);
    padding: 0;
}

.theme-toggle-btn:hover {
    color: var(--accent-color);
    border-color: var(--accent-color);
    transform: rotate(25deg) scale(1.1);
}

/* =========================================
   CARDS & CONTAINERS
   ========================================= */
.modern-card {
    background-color: var(--card-bg);
    border-radius: 14px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-soft);
    padding: 24px;
    margin-bottom: 25px;
    transition: transform 0.25s ease, box-shadow 0.25s ease, border-color 0.25s ease;
}

.modern-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-3px);
}

/* Dark Theme component adjustments (cả [data-theme="dark"] và body.dark-theme) */
[data-theme="dark"] .panel,
[data-theme="dark"] .panel-default,
body.dark-theme .panel,
body.dark-theme .panel-default {
    background-color: var(--card-bg);
    border-color: var(--border-color);
    color: var(--text-color);
}

[data-theme="dark"] .panel-default > .panel-heading,
body.dark-theme .panel-default > .panel-heading {
    background-color: rgba(255, 255, 255, 0.04);
    border-color: var(--border-color);
    color: var(--text-color);
}

[data-theme="dark"] .modern-card,
body.dark-theme .modern-card {
    background-color: var(--card-bg) !important;
    border-color: var(--border-color) !important;
    color: var(--text-color) !important;
}

[data-theme="dark"] .login-card,
body.dark-theme .login-card {
    background-color: var(--card-bg) !important;
    border-color: var(--border-color) !important;
    color: var(--text-color) !important;
}

[data-theme="dark"] .input-custom,
body.dark-theme .input-custom {
    background-color: #0f172a !important;
    border-color: var(--border-color) !important;
    color: var(--text-color) !important;
}

[data-theme="dark"] .table,
body.dark-theme .table {
    color: var(--text-color);
}

[data-theme="dark"] .table-bordered,
[data-theme="dark"] .table-bordered > tbody > tr > td,
[data-theme="dark"] .table-bordered > tbody > tr > th,
[data-theme="dark"] .table-bordered > thead > tr > td,
[data-theme="dark"] .table-bordered > thead > tr > th,
body.dark-theme .table-bordered,
body.dark-theme .table-bordered > tbody > tr > td,
body.dark-theme .table-bordered > tbody > tr > th,
body.dark-theme .table-bordered > thead > tr > td,
body.dark-theme .table-bordered > thead > tr > th {
    border-color: var(--border-color);
}

[data-theme="dark"] .table-striped > tbody > tr:nth-of-type(odd),
body.dark-theme .table-striped > tbody > tr:nth-of-type(odd) {
    background-color: rgba(255, 255, 255, 0.02);
}

[data-theme="dark"] .table > tbody > tr:hover,
body.dark-theme .table > tbody > tr:hover {
    background-color: rgba(255, 255, 255, 0.05);
}

[data-theme="dark"] .form-control,
[data-theme="dark"] input[type="text"],
[data-theme="dark"] input[type="password"],
[data-theme="dark"] input[type="email"],
[data-theme="dark"] textarea,
[data-theme="dark"] select,
body.dark-theme .form-control,
body.dark-theme input[type="text"],
body.dark-theme input[type="password"],
body.dark-theme input[type="email"],
body.dark-theme textarea,
body.dark-theme select {
    background-color: #0f172a;
    border-color: var(--border-color);
    color: var(--text-color);
}

[data-theme="dark"] .form-control:focus,
body.dark-theme .form-control:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(96, 165, 250, 0.25);
}

[data-theme="dark"] .dropdown-menu,
body.dark-theme .dropdown-menu {
    background-color: var(--card-bg);
    border-color: var(--border-color);
    box-shadow: 0 10px 25px rgba(0,0,0,0.5);
}

[data-theme="dark"] .dropdown-menu > li > a,
body.dark-theme .dropdown-menu > li > a {
    color: var(--text-color);
}

[data-theme="dark"] .dropdown-menu > li > a:hover,
[data-theme="dark"] .dropdown-menu > li > a:focus,
body.dark-theme .dropdown-menu > li > a:hover,
body.dark-theme .dropdown-menu > li > a:focus {
    background-color: rgba(255, 255, 255, 0.08);
    color: var(--primary-color);
}

[data-theme="dark"] .dropdown-menu .divider,
body.dark-theme .dropdown-menu .divider {
    background-color: var(--border-color);
}

[data-theme="dark"] .btn-default,
body.dark-theme .btn-default {
    background-color: var(--card-bg);
    color: var(--text-color);
    border-color: var(--border-color);
}

[data-theme="dark"] .btn-default:hover,
body.dark-theme .btn-default:hover {
    background-color: rgba(255, 255, 255, 0.1);
    color: var(--text-color);
    border-color: var(--primary-color);
}

[data-theme="dark"] .list-group-item,
body.dark-theme .list-group-item {
    background-color: var(--card-bg);
    border-color: var(--border-color);
    color: var(--text-color);
}

[data-theme="dark"] .op,
body.dark-theme .op {
    background-color: #1e293b !important;
    border-color: var(--border-color) !important;
    color: var(--text-color) !important;
}

[data-theme="dark"] .op:hover,
body.dark-theme .op:hover {
    background-color: #273549 !important;
    border-color: var(--primary-color) !important;
}

[data-theme="dark"] .modal-content,
body.dark-theme .modal-content {
    background-color: var(--card-bg);
    border-color: var(--border-color);
    color: var(--text-color);
}

[data-theme="dark"] .modal-header,
[data-theme="dark"] .modal-footer,
body.dark-theme .modal-header,
body.dark-theme .modal-footer {
    border-color: var(--border-color);
}

[data-theme="dark"] .alert-info,
body.dark-theme .alert-info {
    background-color: rgba(37, 99, 235, 0.15);
    border-color: rgba(37, 99, 235, 0.3);
    color: #93c5fd;
}

[data-theme="dark"] .alert-warning,
body.dark-theme .alert-warning {
    background-color: rgba(245, 158, 11, 0.15);
    border-color: rgba(245, 158, 11, 0.3);
    color: #fde68a;
}

/* =========================================
   QUIZ BADGES & LABELS
   ========================================= */
.badge-tag {
    display: inline-flex;
    align-items: center;
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-right: 6px;
}

.badge-tag-free {
    background: rgba(16, 185, 129, 0.15);
    color: #10b981;
}

.badge-tag-thpt {
    background: rgba(245, 158, 11, 0.15);
    color: #f59e0b;
}

.badge-tag-pro {
    background: rgba(99, 102, 241, 0.15);
    color: #6366f1;
}

/* =========================================
   MOBILE BOTTOM NAVIGATION BAR
   ========================================= */
.mobile-bottom-nav {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    width: 100%;
    background: var(--nav-bg);
    backdrop-filter: blur(15px);
    -webkit-backdrop-filter: blur(15px);
    border-top: 1px solid var(--border-color);
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.08);
    z-index: 9998;
    padding: 6px 0 8px 0;
}

.mobile-bottom-nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: space-around;
    align-items: center;
}

.mobile-bottom-nav li {
    flex: 1;
    text-align: center;
}

.mobile-bottom-nav a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 11px;
    font-weight: 500;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 3px;
    transition: color 0.2s ease, transform 0.2s ease;
}

.mobile-bottom-nav a i {
    font-size: 19px;
}

.mobile-bottom-nav a.active,
.mobile-bottom-nav a:hover {
    color: var(--primary-color);
}

.mobile-bottom-nav a.active i {
    transform: scale(1.15);
}

@media (max-width: 768px) {
    .mobile-bottom-nav {
        display: block;
    }
    body {
        padding-bottom: 65px;
    }
}