/* ==========================================================================
   Gradient-Free-Optimizers Custom Theme
   A scientific, modern theme with deep and light blues
   ========================================================================== */

/* -- CSS Variables --------------------------------------------------------- */

:root {
    /* Primary palette - Deep ocean blues */
    --gfo-primary: #1a365d;
    --gfo-primary-light: #2c5282;
    --gfo-secondary: #2b6cb0;
    --gfo-accent: #4299e1;
    --gfo-accent-light: #63b3ed;

    /* Gradient colors */
    --gfo-gradient-start: #1a365d;
    --gfo-gradient-mid: #2b6cb0;
    --gfo-gradient-end: #63b3ed;

    /* Category colors */
    --gfo-local: #e53e3e;      /* Red for local search */
    --gfo-global: #38a169;     /* Green for global search */
    --gfo-population: #805ad5; /* Purple for population */
    --gfo-smbo: #dd6b20;       /* Orange for SMBO */

    /* Neutral colors */
    --gfo-text: #2d3748;
    --gfo-text-muted: #718096;
    --gfo-bg: #ffffff;
    --gfo-bg-alt: #f7fafc;
    --gfo-border: #e2e8f0;

    /* Shadows */
    --gfo-shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --gfo-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --gfo-shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --gfo-shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

/* Dark mode variables */
html[data-theme="dark"] {
    --gfo-primary: #90cdf4;
    --gfo-primary-light: #63b3ed;
    --gfo-secondary: #4299e1;
    --gfo-accent: #63b3ed;
    --gfo-accent-light: #90cdf4;

    --gfo-gradient-start: #2d3748;
    --gfo-gradient-mid: #2b6cb0;
    --gfo-gradient-end: #3182ce;

    --gfo-text: #e2e8f0;
    --gfo-text-muted: #a0aec0;
    --gfo-bg: #1a202c;
    --gfo-bg-alt: #2d3748;
    --gfo-border: #4a5568;
}

/* -- PyData Theme Overrides ------------------------------------------------ */

:root {
    --pst-color-primary: var(--gfo-secondary);
    --pst-color-link: var(--gfo-secondary);
    --pst-color-link-hover: var(--gfo-accent);
}

html[data-theme="dark"] {
    --pst-color-primary: var(--gfo-accent);
    --pst-color-link: var(--gfo-accent);
    --pst-color-link-hover: var(--gfo-accent-light);
}

/* -- Top Navbar ------------------------------------------------------------ */

.bd-header.navbar {
    padding-top: 0 !important;
    padding-bottom: 0 !important;
    min-height: auto !important;
    border-bottom: 1px solid var(--gfo-border);
}

.bd-header .navbar-header-items {
    flex-wrap: nowrap !important;
}

.bd-header .navbar-header-items__center {
    flex-wrap: nowrap !important;
}

.bd-header .navbar-header-items__start {
    padding-top: 0 !important;
    padding-bottom: 0 !important;
}

.navbar-brand {
    padding: 0.25rem 0 !important;
    margin-right: 0.75rem !important;
    flex-shrink: 0 !important;
}

.navbar-brand .logo__image {
    height: 36px !important;
    width: auto !important;
    max-height: 36px !important;
    display: inline-block !important;
    visibility: visible !important;
    opacity: 1 !important;
}

.navbar-brand p,
.navbar-brand .logo__title {
    display: none !important;
}

.bd-navbar .navbar-nav {
    flex-wrap: nowrap !important;
}

.bd-navbar .nav-link {
    padding: 0.4rem 0.5rem !important;
    white-space: nowrap;
    font-size: 0.85rem;
}

.bd-navbar .dropdown-toggle {
    padding: 0.4rem 0.5rem !important;
    font-size: 0.85rem;
}

/* -- Back to Top Link (in sidebar) ---------------------------------------- */

.back-to-top-sidebar {
    display: none;
    margin-top: 1.5rem;
    padding-top: 1rem;
    border-top: 1px solid var(--gfo-border);
}

.back-to-top-sidebar.visible {
    display: block;
}

.back-to-top-sidebar a {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--gfo-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    font-weight: 500;
    transition: color 0.2s ease;
}

.back-to-top-sidebar a:hover {
    color: var(--gfo-accent);
}

html[data-theme="dark"] .back-to-top-sidebar a {
    color: var(--gfo-accent);
}

html[data-theme="dark"] .back-to-top-sidebar a:hover {
    color: var(--gfo-accent-light);
}

/* -- Right Sidebar - TOC -------------------------------------------------- */

.bd-toc-nav.page-toc {
    margin-top: 1.25rem;
}

/* Remove per-entry indicator line from right sidebar */
.bd-sidebar-secondary .toc-entry,
.bd-sidebar-secondary nav.page-toc {
    border-left: none;
}

/* Right sidebar slide-in animation on page load */
@keyframes slideInFromLeft {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.bd-sidebar-secondary {
    min-width: 200px;
    animation: slideInFromLeft 0.3s ease forwards;
}

.pst-page-navigation-heading {
    margin-bottom: 0.5rem;
}

/* -- Section Separators ---------------------------------------------------- */

hr {
    border: none;
    height: 1px;
    background-color: var(--gfo-border);
    margin: 2.5rem 0;
    width: 100%;
}

/* -- Section Spacing ------------------------------------------------------- */

.bd-article-container h2 {
    margin-top: 3rem;
}

/* -- Hero Section ---------------------------------------------------------- */

.hero-section {
    background: linear-gradient(135deg, var(--gfo-gradient-start) 0%, var(--gfo-gradient-mid) 50%, var(--gfo-gradient-end) 100%);
    padding: 4rem 2rem;
    text-align: center;
    color: white;
    margin: -1rem -1rem 2rem -1rem;
    border-radius: 0 0 20px 20px;
    position: relative;
    overflow: hidden;
}

.hero-section::before {
    content: "";
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at 30% 70%, rgba(255,255,255,0.1) 0%, transparent 50%);
    animation: pulse 15s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { transform: scale(1); opacity: 0.5; }
    50% { transform: scale(1.1); opacity: 0.3; }
}

.hero-title {
    font-size: 3rem;
    font-weight: 200;
    margin: 0 0 3.5rem 0;
    position: relative;
    z-index: 1;
    line-height: 1.1;
}

.hero-tagline {
    font-size: 1.25rem;
    font-weight: 400;
    color: rgba(210, 215, 225, 0.95);
    max-width: 600px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
    letter-spacing: 0.05em;
    font-style: italic;
}

/* -- Stats Strip ----------------------------------------------------------- */

.stats-strip {
    display: flex;
    justify-content: center;
    align-items: stretch;
    gap: 0;
    margin: 0 0 2rem 0;
    padding: 0;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: var(--gfo-shadow);
    border: 1px solid var(--gfo-border);
    background: var(--gfo-bg);
}

html[data-theme="dark"] .stats-strip {
    background: var(--gfo-bg-alt);
}

.stat-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 1.25rem 1rem;
    text-align: center;
    position: relative;
    transition: background 0.2s ease;
    min-height: 85px;
}

.stat-item:not(:last-child)::after {
    content: '';
    position: absolute;
    right: 0;
    top: 20%;
    height: 60%;
    width: 1px;
    background: var(--gfo-border);
}

.stat-item:hover {
    background: var(--gfo-bg-alt);
}

html[data-theme="dark"] .stat-item:hover {
    background: var(--gfo-bg);
}

a.stat-item {
    text-decoration: none;
    color: inherit;
}

/* Front content (number + label) */
.stat-front {
    display: flex;
    flex-direction: column;
    align-items: center;
    transition: opacity 0.25s ease, transform 0.25s ease;
}

.stat-item:hover .stat-front {
    opacity: 0;
    transform: translateY(-8px);
}

/* Hover content (description) */
.stat-hover {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem;
    opacity: 0;
    transform: translateY(8px);
    transition: opacity 0.25s ease, transform 0.25s ease;
    pointer-events: none;
}

.stat-item:hover .stat-hover {
    opacity: 1;
    transform: translateY(0);
}

.stat-hover-text {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--gfo-secondary);
    line-height: 1.4;
    text-align: center;
}

html[data-theme="dark"] .stat-hover-text {
    color: var(--gfo-accent);
}

.stat-value {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--gfo-secondary);
    line-height: 1.2;
    margin-bottom: 0.25rem;
    text-transform: lowercase;
}

html[data-theme="dark"] .stat-value {
    color: var(--gfo-accent);
}

.stat-label {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--gfo-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* -- Category Cards -------------------------------------------------------- */

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    padding: 1rem 0;
}

.category-card {
    background: var(--gfo-bg);
    border: 1px solid var(--gfo-border);
    border-radius: 12px;
    padding: 1.5rem;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.category-card::before {
    content: "";
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 4px;
    background: var(--category-color, var(--gfo-accent));
}

.category-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--gfo-shadow-lg);
    border-color: var(--category-color, var(--gfo-accent));
}

.category-card.local { --category-color: var(--gfo-local); }
.category-card.global { --category-color: var(--gfo-global); }
.category-card.population { --category-color: var(--gfo-population); }
.category-card.smbo { --category-color: var(--gfo-smbo); }

.category-header {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.category-icon {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--category-color, var(--gfo-accent));
    color: white;
    font-size: 1.25rem;
}

.category-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--gfo-text);
    margin: 0;
}

.category-count {
    font-size: 0.85rem;
    color: var(--gfo-text-muted);
    margin-left: auto;
}

.category-description {
    color: var(--gfo-text-muted);
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 1rem;
}

.category-algorithms {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.algorithm-tag {
    background: var(--gfo-bg-alt);
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.8rem;
    color: var(--gfo-text-muted);
    transition: all 0.2s ease;
}

.algorithm-tag:hover {
    background: var(--category-color, var(--gfo-accent));
    color: white;
}

/* -- Feature Cards --------------------------------------------------------- */

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
    padding: 2rem 0;
}

.feature-card {
    background: var(--gfo-bg);
    border: 1px solid var(--gfo-border);
    border-radius: 12px;
    padding: 1.5rem;
    transition: all 0.3s ease;
}

.feature-card:hover {
    border-color: var(--gfo-accent);
    box-shadow: var(--gfo-shadow);
}

.feature-icon {
    width: 48px;
    height: 48px;
    border-radius: 10px;
    background: linear-gradient(135deg, var(--gfo-secondary) 0%, var(--gfo-accent) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

.feature-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--gfo-text);
    margin-bottom: 0.5rem;
}

.feature-description {
    color: var(--gfo-text-muted);
    font-size: 0.95rem;
    line-height: 1.6;
}

/* -- Algorithm Page Cards -------------------------------------------------- */

.algorithm-card {
    background: var(--gfo-bg);
    border: 1px solid var(--gfo-border);
    border-radius: 16px;
    overflow: hidden;
    transition: all 0.3s ease;
}

.algorithm-card:hover {
    box-shadow: var(--gfo-shadow-xl);
    transform: translateY(-2px);
}

.algorithm-gif {
    width: 100%;
    height: auto;
    display: block;
    background: var(--gfo-bg-alt);
}

.algorithm-content {
    padding: 1.5rem;
}

.algorithm-name {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--gfo-text);
    margin-bottom: 0.5rem;
}

.algorithm-category-badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 1rem;
}

.algorithm-category-badge.local { background: rgba(229, 62, 62, 0.1); color: var(--gfo-local); }
.algorithm-category-badge.global { background: rgba(56, 161, 105, 0.1); color: var(--gfo-global); }
.algorithm-category-badge.population { background: rgba(128, 90, 213, 0.1); color: var(--gfo-population); }
.algorithm-category-badge.smbo { background: rgba(221, 107, 32, 0.1); color: var(--gfo-smbo); }

/* -- Quick Install Tabs ---------------------------------------------------- */

.install-tabs {
    display: flex;
    gap: 0.5rem;
    background: var(--gfo-bg-alt);
    padding: 0.25rem;
    border-radius: 8px;
    margin-bottom: 1rem;
}

.install-tab {
    padding: 0.5rem 1rem;
    border-radius: 6px;
    border: none;
    background: transparent;
    color: var(--gfo-text-muted);
    cursor: pointer;
    transition: all 0.2s ease;
    font-size: 0.9rem;
}

.install-tab:hover {
    color: var(--gfo-text);
}

.install-tab.active {
    background: var(--gfo-bg);
    color: var(--gfo-secondary);
    box-shadow: var(--gfo-shadow-sm);
}

/* -- Code Blocks ----------------------------------------------------------- */

.highlight {
    background: var(--gfo-bg-alt) !important;
    border-radius: 8px;
    border: 1px solid var(--gfo-border);
}

.highlight pre {
    padding: 1rem;
    margin: 0;
    overflow-x: auto;
}

/* -- Comparison Table ------------------------------------------------------ */

.comparison-table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    border-radius: 12px;
    overflow: hidden;
    border: 1px solid var(--gfo-border);
}

.comparison-table th {
    background: linear-gradient(135deg, var(--gfo-primary) 0%, var(--gfo-secondary) 100%);
    color: white;
    padding: 1rem;
    text-align: left;
    font-weight: 600;
}

.comparison-table td {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--gfo-border);
}

.comparison-table tr:last-child td {
    border-bottom: none;
}

.comparison-table tr:nth-child(even) {
    background: var(--gfo-bg-alt);
}

/* -- API Interface Tabs ---------------------------------------------------- */

.api-tabs {
    display: flex;
    border-bottom: 2px solid var(--gfo-border);
    margin-bottom: 1.5rem;
}

.api-tab {
    padding: 0.75rem 1.5rem;
    border: none;
    background: transparent;
    color: var(--gfo-text-muted);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 500;
    position: relative;
    transition: all 0.2s ease;
}

.api-tab:hover {
    color: var(--gfo-text);
}

.api-tab.active {
    color: var(--gfo-secondary);
}

.api-tab.active::after {
    content: "";
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gfo-secondary);
}

/* -- Parameter Tables ------------------------------------------------------ */

.param-table {
    width: 100%;
    margin: 1rem 0;
}

.param-table th {
    background: var(--gfo-bg-alt);
    padding: 0.75rem 1rem;
    text-align: left;
    font-weight: 600;
    color: var(--gfo-text);
    border-bottom: 2px solid var(--gfo-border);
}

.param-table td {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--gfo-border);
    vertical-align: top;
}

.param-name {
    font-family: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    font-size: 0.9rem;
    color: var(--gfo-secondary);
    background: var(--gfo-bg-alt);
    padding: 0.1rem 0.4rem;
    border-radius: 4px;
}

.param-type {
    font-size: 0.85rem;
    color: var(--gfo-text-muted);
    font-style: italic;
}

.param-default {
    font-family: monospace;
    font-size: 0.85rem;
    color: var(--gfo-accent);
}

/* -- Navigation Cards ------------------------------------------------------ */

.nav-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
    margin: 2rem 0;
}

.nav-card {
    background: var(--gfo-bg);
    border: 1px solid var(--gfo-border);
    border-radius: 12px;
    padding: 1.25rem;
    text-decoration: none;
    color: var(--gfo-text);
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 1rem;
}

.nav-card:hover {
    border-color: var(--gfo-accent);
    box-shadow: var(--gfo-shadow);
    transform: translateX(4px);
    text-decoration: none;
    color: var(--gfo-text);
}

.nav-card-icon {
    width: 40px;
    height: 40px;
    border-radius: 8px;
    background: var(--gfo-bg-alt);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--gfo-secondary);
    font-size: 1.25rem;
    flex-shrink: 0;
}

.nav-card-content {
    flex: 1;
}

.nav-card-title {
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.nav-card-description {
    font-size: 0.85rem;
    color: var(--gfo-text-muted);
}

.nav-card-arrow {
    color: var(--gfo-text-muted);
    transition: transform 0.2s ease;
}

.nav-card:hover .nav-card-arrow {
    transform: translateX(4px);
    color: var(--gfo-accent);
}

/* -- Badges Section -------------------------------------------------------- */

.badge-strip {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
    margin: 1.5rem 0;
}

.badge-strip img {
    height: 20px;
}

/* -- Responsive Adjustments ------------------------------------------------ */

@media (max-width: 768px) {
    .hero-section {
        padding: 2.5rem 1rem;
    }

    .hero-title {
        font-size: 2rem;
    }

    .stats-strip {
        flex-wrap: wrap;
    }

    .stat-item {
        flex: 1 1 50%;
        padding: 1rem 0.75rem;
        min-height: 75px;
    }

    .stat-item:not(:last-child)::after {
        display: none;
    }

    .stat-item:nth-child(1),
    .stat-item:nth-child(2) {
        border-bottom: 1px solid var(--gfo-border);
    }

    .stat-item:nth-child(odd) {
        border-right: 1px solid var(--gfo-border);
    }

    .stat-value {
        font-size: 1.5rem;
    }

    .stat-hover-text {
        font-size: 0.75rem;
    }

    .category-grid,
    .feature-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 1.75rem;
    }

    .hero-tagline {
        font-size: 1rem;
    }
}

/* -- Compact dimension cards (search spaces page) ------------------------- */

.sd-card.gfo-compact .sd-card-body {
    padding: 0.6rem 1rem !important;
}

.sd-card.gfo-compact .sd-card-title {
    margin-bottom: 0.2rem !important;
    font-size: 0.95rem;
}

.sd-card.gfo-compact .sd-row {
    --sd-gutter-x: 0 !important;
    --sd-gutter-y: 0 !important;
    align-items: center;
}

.sd-card.gfo-compact .highlight {
    margin-bottom: 0 !important;
    margin-top: 0 !important;
}

.sd-card.gfo-compact .highlight pre {
    padding: 0.5rem 0.75rem !important;
}

.sd-card.gfo-compact p {
    margin-bottom: 0 !important;
}

/* -- Category-colored sphinx-design cards ---------------------------------- */

.sd-card.gfo-local { border-color: var(--gfo-local) !important; }
.sd-card.gfo-global { border-color: var(--gfo-global) !important; }
.sd-card.gfo-population { border-color: var(--gfo-population) !important; }
.sd-card.gfo-smbo { border-color: var(--gfo-smbo) !important; }

/* -- sphinx-design overrides ----------------------------------------------- */

.sd-card {
    border-radius: 12px !important;
    border: 1px solid var(--gfo-border) !important;
    transition: all 0.3s ease !important;
}

.sd-card:hover {
    border-color: var(--gfo-accent) !important;
    box-shadow: var(--gfo-shadow) !important;
}

.sd-card-header {
    background: transparent !important;
    border-bottom: 1px solid var(--gfo-border) !important;
    padding: 1rem 1.25rem !important;
}

.sd-card-body {
    padding: 1.25rem !important;
}

.sd-card-footer {
    background: var(--gfo-bg-alt) !important;
    border-top: 1px solid var(--gfo-border) !important;
    padding: 0.75rem 1.25rem !important;
}

/* Tab styling */
.sd-tab-set > input:checked + label {
    border-color: var(--gfo-secondary) !important;
    color: var(--gfo-secondary) !important;
}

.sd-tab-label:hover {
    border-color: var(--gfo-accent) !important;
    color: var(--gfo-accent) !important;
}

/* -- Admonition styling ---------------------------------------------------- */

.admonition {
    border-radius: 8px !important;
    border-left-width: 4px !important;
}

.admonition.tip {
    border-left-color: var(--gfo-accent) !important;
}

.admonition.note {
    border-left-color: var(--gfo-secondary) !important;
}

.admonition.warning {
    border-left-color: var(--gfo-local) !important;
}

/* -- Section headers ------------------------------------------------------- */

h1 {
    font-weight: 600;
    color: var(--gfo-text);
}

/* Home page h1s - underline style (matching section headers) */
article:has(.hero-section) h1:not(.hero-title) {
    padding-bottom: 0.4rem;
    border-bottom: 1px solid var(--pst-color-border);
}

h2 {
    font-weight: 600;
    color: var(--gfo-text);
    margin-top: 2rem;
}

h3 {
    font-weight: 600;
    color: var(--gfo-text-muted);
}

/* -- Links ----------------------------------------------------------------- */

a {
    color: var(--gfo-secondary);
    text-decoration: none;
    transition: color 0.2s ease;
}

a:hover {
    color: var(--gfo-accent);
}

/* -- Footer ---------------------------------------------------------------- */

.bd-footer {
    border-top: 1px solid var(--gfo-border);
    padding: 2rem 0;
    margin-top: 3rem;
}

/* -- Algorithm list styling ------------------------------------------------ */

.algorithm-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.algorithm-list-item {
    display: flex;
    align-items: center;
    padding: 0.75rem 1rem;
    border: 1px solid var(--gfo-border);
    border-radius: 8px;
    margin-bottom: 0.5rem;
    transition: all 0.2s ease;
}

.algorithm-list-item:hover {
    border-color: var(--gfo-accent);
    background: var(--gfo-bg-alt);
}

.algorithm-list-item a {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    text-decoration: none;
    color: var(--gfo-text);
}

.algorithm-list-item a:hover {
    color: var(--gfo-secondary);
}

/* -- GIF display styling --------------------------------------------------- */

.gif-container {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 1rem;
    margin: 1.5rem 0;
}

.gif-wrapper {
    background: var(--gfo-bg-alt);
    border: 1px solid var(--gfo-border);
    border-radius: 12px;
    overflow: hidden;
}

.gif-wrapper img {
    width: 100%;
    height: auto;
    display: block;
}

.gif-caption {
    padding: 0.75rem;
    text-align: center;
    font-size: 0.9rem;
    color: var(--gfo-text-muted);
    border-top: 1px solid var(--gfo-border);
}

@media (max-width: 640px) {
    .gif-container {
        grid-template-columns: 1fr;
    }
}

/* -- Back to top ----------------------------------------------------------- */

.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--gfo-secondary);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    box-shadow: var(--gfo-shadow-lg);
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 1000;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: var(--gfo-accent);
    transform: translateY(-4px);
    color: white;
}