:root {
    --app-bg: #f6f8fa;
    --app-surface: #ffffff;
    --app-surface-muted: #eef7f5;
    --app-border: #d9e2df;
    --app-text: #18201f;
    --app-muted: #64706d;
    --app-primary: #0f766e;
    --app-primary-hover: #0b5f59;
    --app-accent: #e11d48;
    --app-warning: #c98100;
    --app-shadow: 0 10px 28px rgba(24, 32, 31, 0.08);
    --app-shadow-sm: 0 4px 14px rgba(24, 32, 31, 0.06);
    --primary-color: var(--app-primary);
    --secondary-color: var(--app-bg);
    --accent-color: #f4b740;
}

* {
    letter-spacing: 0;
}

body {
    --primary-color: var(--app-primary);
    --secondary-color: var(--app-bg);
    --accent-color: #f4b740;
    background:
        linear-gradient(180deg, rgba(15, 118, 110, 0.08), rgba(246, 248, 250, 0) 280px),
        var(--app-bg) !important;
    color: var(--app-text);
}

.container {
    max-width: 1180px;
}

.navbar {
    background: rgba(255, 255, 255, 0.94) !important;
    border-bottom: 1px solid var(--app-border);
    box-shadow: 0 1px 0 rgba(24, 32, 31, 0.04);
    backdrop-filter: blur(12px);
}

.navbar-brand {
    color: var(--app-text) !important;
    font-weight: 750 !important;
}

.navbar-dark .navbar-nav .nav-link,
.navbar .nav-link {
    color: var(--app-muted) !important;
    border-radius: 8px;
    padding-left: 0.75rem !important;
    padding-right: 0.75rem !important;
}

.navbar-dark .navbar-nav .nav-link.active,
.navbar .nav-link.active,
.navbar .nav-link:hover {
    color: var(--app-primary) !important;
    background: var(--app-surface-muted);
}

.navbar-dark .navbar-toggler {
    border-color: var(--app-border);
    filter: invert(1);
}

h1, h2, h3, h4, h5, h6 {
    color: var(--app-text);
}

.text-muted {
    color: var(--app-muted) !important;
}

.btn {
    border-radius: 8px;
    font-weight: 650;
}

.btn-primary,
.btn-success {
    background-color: var(--app-primary) !important;
    border-color: var(--app-primary) !important;
}

.btn-primary:hover,
.btn-success:hover {
    background-color: var(--app-primary-hover) !important;
    border-color: var(--app-primary-hover) !important;
}

.btn-outline-primary {
    color: var(--app-primary) !important;
    border-color: var(--app-primary) !important;
}

.btn-outline-primary:hover {
    color: #fff !important;
    background-color: var(--app-primary) !important;
}

.btn-outline-secondary {
    color: var(--app-muted);
    border-color: var(--app-border);
}

.btn-outline-secondary:hover {
    color: var(--app-text);
    background: #edf2f1;
    border-color: #cbd8d5;
}

.card,
.form-section,
.series-nav,
.book-panel,
.result-panel,
.summary-item,
.login-container,
.unit-card,
.series-selector,
.summary-item,
.knowledge-preview-stat {
    border: 1px solid var(--app-border) !important;
    border-radius: 8px !important;
    box-shadow: var(--app-shadow-sm) !important;
}

.card {
    overflow: hidden;
}

.card:hover,
.series-card:hover {
    transform: translateY(-2px) !important;
    box-shadow: var(--app-shadow) !important;
}

.card-img-container {
    background: #e8efed !important;
}

.card-title {
    color: var(--app-text);
    font-weight: 750;
}

.form-control,
.form-select {
    border-color: var(--app-border);
    border-radius: 8px;
}

.form-control:focus,
.form-select:focus {
    border-color: var(--app-primary);
    box-shadow: 0 0 0 0.2rem rgba(15, 118, 110, 0.14);
}

.form-section {
    background: rgba(255, 255, 255, 0.96) !important;
}

.section-title {
    color: var(--app-primary);
    border-bottom-color: var(--app-border) !important;
}

.dynamic-field-group {
    border-color: var(--app-border) !important;
    border-radius: 8px !important;
    background-color: #fbfcfc !important;
}

.grade-badge,
.difficulty-badge,
.badge.bg-light {
    background: var(--app-surface-muted) !important;
    color: var(--app-primary) !important;
    border: 1px solid rgba(15, 118, 110, 0.18);
    border-radius: 8px;
}

.tag-stat {
    border-radius: 8px !important;
    box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.35);
}

.empty-state,
#emptyState {
    background: rgba(255, 255, 255, 0.72);
    border: 1px dashed var(--app-border);
    border-radius: 8px;
}

.book-header,
.result-header {
    background: #fbfcfc !important;
}

.unit-row,
.knowledge-unit-row {
    background: #fff;
}

.unit-row:hover,
.knowledge-unit-row:hover {
    background: #f7fbfa;
}

.knowledge-tree {
    border-color: var(--app-border) !important;
    box-shadow: var(--app-shadow-sm);
}

.knowledge-series > summary {
    background: var(--app-surface-muted) !important;
    color: var(--app-text);
}

.knowledge-book > summary {
    background: #fff;
}

.modal-content {
    border: 1px solid var(--app-border);
    border-radius: 8px;
    box-shadow: var(--app-shadow);
}

.modal-header {
    border-bottom-color: var(--app-border);
}

.modal-footer {
    border-top-color: var(--app-border);
}

.alert {
    border-radius: 8px;
}

.table {
    color: var(--app-text);
}

.table thead th {
    color: var(--app-muted);
    font-weight: 700;
}

.login-page {
    min-height: 100vh;
    display: grid;
    grid-template-columns: minmax(320px, 460px) minmax(0, 1fr);
}

.login-container {
    width: min(420px, calc(100% - 2rem));
    margin: auto;
    padding: 2rem;
    background: rgba(255, 255, 255, 0.96) !important;
}

.login-logo h1 {
    color: var(--app-primary) !important;
    font-weight: 800 !important;
}

.login-visual {
    min-height: 100vh;
    background:
        linear-gradient(90deg, rgba(15, 118, 110, 0.70), rgba(15, 118, 110, 0.12)),
        url("https://images.unsplash.com/photo-1503676260728-1c00da094a0b?auto=format&fit=crop&w=1500&q=80") center/cover;
    display: flex;
    align-items: end;
    padding: 3rem;
}

.login-visual-copy {
    color: white;
    max-width: 520px;
    text-shadow: 0 2px 16px rgba(0, 0, 0, 0.22);
}

.login-visual-copy h2 {
    color: white;
    font-size: 2.4rem;
    font-weight: 800;
}

@media (max-width: 900px) {
    .login-page {
        grid-template-columns: 1fr;
    }

    .login-visual {
        min-height: 260px;
        order: -1;
        padding: 2rem;
    }

    .login-visual-copy h2 {
        font-size: 1.8rem;
    }
}