:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --secondary: #0f172a;
    --accent: #14b8a6;
    --success: #16a34a;
    --warning: #f59e0b;
    --danger: #dc2626;
    --background: #f4f7fb;
    --surface: #ffffff;
    --surface-soft: #f8fafc;
    --border: #e2e8f0;
    --text: #0f172a;
    --muted: #64748b;
    --sidebar-bg: #0f172a;
    --sidebar-soft: #1e293b;
    --shadow-soft: 0 12px 32px rgba(15, 23, 42, 0.08);
    --shadow-card: 0 18px 40px rgba(15, 23, 42, 0.08);
    --radius-xl: 28px;
    --radius-lg: 22px;
    --radius-md: 16px;
    --radius-sm: 12px;
    --content-max: 1680px;
}

body.app-body {
    font-family: "Inter", "Segoe UI", Arial, sans-serif;
    color: var(--text);
    background:
        radial-gradient(circle at top left, rgba(37, 99, 235, 0.08), transparent 28%),
        radial-gradient(circle at bottom right, rgba(20, 184, 166, 0.08), transparent 24%),
        var(--background);
}

.app-shell {
    grid-template-columns: 300px minmax(0, 1fr);
    background: transparent;
}

.main-area {
    min-width: 0;
    display: grid;
    grid-template-rows: auto 1fr;
}

.sidebar {
    background:
        linear-gradient(180deg, rgba(15, 23, 42, 0.98), rgba(30, 41, 59, 0.96));
    border-right: 1px solid rgba(148, 163, 184, 0.16);
    padding: 26px 20px;
    gap: 20px;
}

.sidebar-brand {
    padding: 4px 4px 10px;
}

.brand-mark {
    background: linear-gradient(135deg, var(--primary), var(--accent));
    color: #fff;
    box-shadow: 0 14px 28px rgba(37, 99, 235, 0.28);
}

.sidebar-intro {
    padding: 16px;
    border-radius: 18px;
    background: rgba(148, 163, 184, 0.08);
    border: 1px solid rgba(148, 163, 184, 0.12);
    display: grid;
    gap: 6px;
}

.sidebar-intro strong {
    color: #f8fafc;
}

.sidebar-intro p {
    color: rgba(226, 232, 240, 0.72);
    line-height: 1.55;
    font-size: 0.92rem;
}

.sidebar-nav {
    gap: 18px;
}

.nav-group {
    display: grid;
    gap: 10px;
}

.nav-group-title {
    padding: 0 12px;
    color: rgba(148, 163, 184, 0.9);
    font-size: 0.74rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.12em;
}

.nav-group-links {
    display: grid;
    gap: 6px;
}

.nav-link {
    min-height: 48px;
    padding: 12px 14px;
    border-radius: 16px;
    color: rgba(226, 232, 240, 0.8);
    justify-content: flex-start;
    transition: background-color 160ms ease, color 160ms ease, transform 160ms ease, box-shadow 160ms ease;
}

.nav-link:hover {
    background: rgba(148, 163, 184, 0.12);
    color: #fff;
    transform: translateX(2px);
}

.nav-link.active {
    background: linear-gradient(135deg, rgba(37, 99, 235, 0.22), rgba(20, 184, 166, 0.16));
    color: #fff;
    box-shadow: inset 0 0 0 1px rgba(96, 165, 250, 0.22);
}

.nav-icon {
    width: 28px;
    min-width: 28px;
    height: 28px;
    display: inline-grid;
    place-items: center;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.08);
    font-size: 0.9rem;
    font-weight: 800;
}

.nav-link.active .nav-icon {
    background: rgba(255, 255, 255, 0.16);
}

.nav-text {
    white-space: normal;
}

.user-chip {
    background: rgba(148, 163, 184, 0.08);
    border: 1px solid rgba(148, 163, 184, 0.12);
}

.content {
    width: min(100%, var(--content-max));
    margin: 0 auto;
    padding: 0 24px 32px;
    display: grid;
    gap: 22px;
    align-content: start;
}

.topbar {
    position: sticky;
    top: 0;
    z-index: 12;
    margin: 18px 24px 18px;
    padding: 18px 22px;
    border-radius: 24px;
    border: 1px solid rgba(226, 232, 240, 0.82);
    background: rgba(255, 255, 255, 0.88);
    backdrop-filter: blur(18px);
    box-shadow: var(--shadow-soft);
}

.topbar-copy {
    gap: 2px;
}

.topbar-copy h1 {
    font-size: clamp(1.8rem, 2.6vw, 2.5rem);
    font-family: "Inter", "Segoe UI", Arial, sans-serif;
    font-weight: 800;
    color: var(--secondary);
}

.topbar-description {
    color: var(--muted);
    font-size: 0.96rem;
    line-height: 1.55;
}

.topbar-user-card {
    display: inline-flex;
    align-items: center;
    gap: 12px;
    padding: 10px 14px;
    border-radius: 16px;
    border: 1px solid var(--border);
    background: var(--surface-soft);
}

.topbar-user-avatar {
    width: 40px;
    height: 40px;
    border-radius: 14px;
    display: grid;
    place-items: center;
    background: linear-gradient(135deg, var(--primary), var(--accent));
    color: #fff;
    font-weight: 800;
}

.topbar-user-meta {
    display: grid;
    gap: 2px;
}

.topbar-user-meta strong {
    color: var(--text);
    font-size: 0.94rem;
}

.topbar-user-meta small {
    color: var(--muted);
    font-size: 0.8rem;
}

.panel,
.stat-card,
.question-preview-card,
.version-card {
    background: rgba(255, 255, 255, 0.94);
    border: 1px solid rgba(226, 232, 240, 0.95);
    box-shadow: var(--shadow-card);
}

.panel {
    padding: 24px;
}

.stats-grid {
    grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
    gap: 18px;
}

.stat-card {
    position: relative;
    overflow: hidden;
}

.stat-card::after {
    content: "";
    position: absolute;
    inset: auto -24px -36px auto;
    width: 104px;
    height: 104px;
    border-radius: 999px;
    background: rgba(37, 99, 235, 0.08);
}

.stat-card strong {
    font-size: clamp(2rem, 3vw, 2.6rem);
    color: var(--secondary);
}

.stat-label {
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-size: 0.76rem;
    font-weight: 800;
}

.btn {
    border-radius: 14px;
    font-weight: 700;
    box-shadow: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
}

.btn-secondary {
    background: var(--surface-soft);
    color: var(--secondary);
    border-color: var(--border);
}

.btn-success {
    background: var(--success);
    color: #fff;
}

.btn-warning {
    background: var(--warning);
    color: #fff;
}

.btn-danger {
    background: var(--danger);
    color: #fff;
}

.table-button,
.table-link {
    display: inline-flex;
    align-items: center;
    min-height: 34px;
    padding: 0 10px;
    border-radius: 10px;
    background: rgba(37, 99, 235, 0.08);
    color: var(--primary-dark);
}

.table-button.danger {
    background: rgba(220, 38, 38, 0.08);
}

.data-table {
    min-width: 940px;
}

.data-table th {
    background: var(--surface-soft);
    color: var(--muted);
    position: sticky;
    top: 0;
}

.data-table tbody tr:hover {
    background: rgba(37, 99, 235, 0.04);
}

label span {
    color: var(--secondary);
    font-size: 0.9rem;
}

input,
select,
textarea {
    border: 1px solid var(--border);
    background: #fff;
    border-radius: 14px;
    min-height: 52px;
}

input:focus,
select:focus,
textarea:focus {
    outline: 3px solid rgba(37, 99, 235, 0.12);
    border-color: rgba(37, 99, 235, 0.45);
}

.checkbox-chip,
.radio-chip,
.toggle-box {
    background: var(--surface-soft);
    border-color: var(--border);
}

.status-badge {
    border-radius: 999px;
    padding: 8px 12px;
}

.alert {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 14px;
    padding: 16px 18px;
    border-radius: 18px;
    border: 1px solid transparent;
    box-shadow: var(--shadow-soft);
}

.alert-copy {
    line-height: 1.55;
    font-weight: 600;
}

.alert-close {
    border: 0;
    background: transparent;
    cursor: pointer;
    color: inherit;
    font-size: 1.2rem;
    line-height: 1;
}

.alert-success {
    background: rgba(22, 163, 74, 0.08);
    color: #166534;
    border-color: rgba(22, 163, 74, 0.14);
}

.alert-danger {
    background: rgba(220, 38, 38, 0.08);
    color: #991b1b;
    border-color: rgba(220, 38, 38, 0.14);
}

.alert-warning {
    background: rgba(245, 158, 11, 0.12);
    color: #92400e;
    border-color: rgba(245, 158, 11, 0.18);
}

.alert-info {
    background: rgba(37, 99, 235, 0.08);
    color: #1d4ed8;
    border-color: rgba(37, 99, 235, 0.14);
}

.empty-state,
.selected-question-empty {
    padding: 24px;
    border-radius: 20px;
    border: 1px dashed rgba(148, 163, 184, 0.42);
    background: linear-gradient(180deg, rgba(248, 250, 252, 0.94), rgba(255, 255, 255, 0.96));
}

.dashboard-overview-grid,
.dashboard-admin-grid,
.dashboard-action-grid {
    display: grid;
    gap: 18px;
}

.dashboard-overview-grid {
    grid-template-columns: minmax(0, 1.5fr) minmax(300px, 0.9fr);
}

.dashboard-hero-card {
    padding: 30px;
    display: grid;
    gap: 20px;
    background:
        radial-gradient(circle at top right, rgba(37, 99, 235, 0.12), transparent 24%),
        linear-gradient(135deg, rgba(255, 255, 255, 0.98), rgba(241, 245, 249, 0.96));
}

.dashboard-hero-copy h2 {
    font-size: clamp(2rem, 3vw, 2.9rem);
    line-height: 1.05;
}

.dashboard-hero-copy p {
    color: var(--muted);
    max-width: 62ch;
    line-height: 1.65;
}

.dashboard-kpi-grid {
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 14px;
}

.dashboard-kpi-card,
.dashboard-mini-card,
.dashboard-action-card {
    padding: 18px;
    border-radius: 18px;
    border: 1px solid var(--border);
    background: #fff;
}

.dashboard-kpi-card strong,
.dashboard-mini-card strong {
    display: block;
    margin-top: 6px;
    font-size: 1.6rem;
}

.dashboard-side-stack {
    display: grid;
    gap: 18px;
}

.dashboard-action-grid {
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
}

.dashboard-action-card {
    display: grid;
    gap: 8px;
    transition: transform 160ms ease, box-shadow 160ms ease;
}

.dashboard-action-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-soft);
}

.dashboard-action-card span {
    color: var(--muted);
    line-height: 1.5;
}

.section-heading h2,
.section-heading h3 {
    color: var(--secondary);
}

.section-heading p {
    color: var(--muted);
}

.form-grid {
    gap: 22px;
}

.panel-accent {
    background:
        radial-gradient(circle at top right, rgba(20, 184, 166, 0.12), transparent 26%),
        linear-gradient(180deg, rgba(255, 255, 255, 0.98), rgba(248, 250, 252, 0.96));
}

.reading-session-stats,
.review-question-list {
    display: grid;
    gap: 18px;
}

.review-question-list {
    margin-top: 18px;
}

.review-question-card {
    gap: 16px;
}

.review-question-meta,
.reading-session-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 10px 14px;
    color: var(--muted);
    font-size: 0.95rem;
}

.reading-session-meta {
    margin-top: 14px;
}

.print-toolbar {
    border-bottom: 1px solid var(--border);
}

@media (max-width: 1200px) {
    .app-shell {
        grid-template-columns: 1fr;
    }

    .main-area {
        min-width: 0;
    }

    .dashboard-overview-grid {
        grid-template-columns: 1fr;
    }

    .dashboard-kpi-grid {
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }
}

@media (max-width: 900px) {
    .topbar {
        margin: 14px 16px 18px;
        padding: 16px;
    }

    .content {
        padding: 0 16px 26px;
    }

    .dashboard-kpi-grid,
    .dashboard-action-grid,
    .adaptation-banner {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: fixed;
        inset: 0 auto 0 0;
        width: min(320px, 88vw);
        height: 100vh;
        z-index: 20;
        transform: translateX(-100%);
        transition: transform 180ms ease;
    }

    .app-shell.menu-open .sidebar {
        transform: translateX(0);
    }

    .sidebar-toggle {
        display: inline-grid;
        place-items: center;
    }
}

@media (max-width: 640px) {
    .content {
        padding: 0 12px 22px;
    }

    .topbar {
        margin: 12px;
        border-radius: 18px;
    }

    .panel,
    .dashboard-hero-card {
        padding: 18px;
    }

    .data-table {
        min-width: 720px;
    }
}