:root {
        --color-primary: #059669;
        --color-primary-hover: rgba(16,185,129,0.15);
        --color-white: #ffffff;
        --color-bg-light: #f8fafc;
        --color-bg-hover: #f1f5f9;
        --color-text-dark: #1e293b;
        --color-text-medium: #475569;
        --color-text-muted: #64748b;
        --color-text-light: #94a3b8;
        --color-border: #e2e8f0;
        --color-success: #10b981;
        --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
        --shadow-green: 0 4px 14px rgba(5,150,105,0.18);
        --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1),0 2px 4px -1px rgba(0,0,0,0.06);
        --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1),0 4px 6px -2px rgba(0,0,0,0.05);
        --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1),0 10px 10px -5px rgba(0,0,0,0.04);
        --border-radius: 12px;
        --border-radius-sm: 8px;
    }

    *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
    body { font-family: 'DM Sans', sans-serif; background: #f8fafc; color: var(--color-text-dark); }

    /* ── Reading progress bar ── */
    .art-progress-bar {
        position: fixed;
        top: 0;
        left: 0;
        height: 3px;
        width: 0%;
        background: linear-gradient(90deg, var(--color-primary), #10b981);
        z-index: 9999;
        transition: width 0.1s linear;
    }

    /* ── Breadcrumb ── */
    .art-breadcrumb {
        background: var(--color-white);
        border-bottom: 1px solid var(--color-border);
        padding: 0.875rem 2rem;
        position: sticky;
        top: 0;
        z-index: 100;
        backdrop-filter: blur(8px);
        background: rgba(255,255,255,0.95);
    }

    .art-breadcrumb-inner {
        max-width: 1200px;
        margin: 0 auto;
        display: flex;
        align-items: center;
        justify-content: space-between;
        gap: 1rem;
        flex-wrap: wrap;
    }

    .art-breadcrumb-nav {
        display: flex;
        align-items: center;
        gap: 0.5rem;
        flex-wrap: wrap;
    }

    .art-breadcrumb-nav a {
        font-size: 0.8125rem;
        color: var(--color-text-muted);
        text-decoration: none;
        font-weight: 500;
        transition: color 0.2s;
        display: flex;
        align-items: center;
        gap: 0.3rem;
    }

    .art-breadcrumb-nav a:hover { color: var(--color-primary); }

    .art-breadcrumb-sep { color: var(--color-text-light); font-size: 0.75rem; }

    .art-breadcrumb-current {
        font-size: 0.8125rem;
        color: var(--color-text-dark);
        font-weight: 600;
        max-width: 300px;
        white-space: nowrap;
        overflow: hidden;
        text-overflow: ellipsis;
    }

    .art-breadcrumb-readtime {
        display: flex;
        align-items: center;
        gap: 0.35rem;
        font-size: 0.75rem;
        color: var(--color-text-muted);
        white-space: nowrap;
    }

    /* ── Layout ── */
    .art-layout {
        max-width: 1200px;
        margin: 0 auto;
        padding: 3rem 2rem 5rem;
        display: grid;
        grid-template-columns: 220px 1fr 240px;
        gap: 3rem;
        align-items: start;
    }

    /* ── Left TOC ── */
    .art-toc {
        position: sticky;
        top: 5rem;
    }

    .art-toc-title {
        font-size: 0.6875rem;
        font-weight: 700;
        text-transform: uppercase;
        letter-spacing: 0.1em;
        color: var(--color-text-muted);
        margin-bottom: 0.875rem;
    }

    .art-toc-list { list-style: none; display: flex; flex-direction: column; gap: 0.125rem; }

    .art-toc-link {
        display: block;
        font-size: 0.8125rem;
        font-weight: 500;
        color: var(--color-text-muted);
        text-decoration: none;
        padding: 0.375rem 0.75rem;
        border-left: 2px solid var(--color-border);
        transition: all 0.2s;
        border-radius: 0 4px 4px 0;
    }

    .art-toc-link:hover {
        color: var(--color-primary);
        border-left-color: var(--color-primary);
        background: var(--color-primary-hover);
    }

    .art-toc-link.active {
        color: var(--color-primary);
        border-left-color: var(--color-primary);
        background: var(--color-primary-hover);
        font-weight: 700;
    }

    /* ── Article main ── */
    .art-main {}

    /* ── Article header ── */
    .art-header {
        background: var(--color-white);
        border: 1.5px solid var(--color-border);
        border-radius: var(--border-radius);
        padding: 2.5rem;
        margin-bottom: 1.5rem;
        animation: artIn 0.5s ease-out both;
    }

    @keyframes artIn {
        from { opacity:0; transform:translateY(16px); }
        to   { opacity:1; transform:translateY(0); }
    }

    .art-header-tags {
        display: flex;
        gap: 0.4rem;
        flex-wrap: wrap;
        margin-bottom: 1rem;
    }

    .art-tag {
        font-size: 0.6875rem;
        font-weight: 700;
        text-transform: uppercase;
        letter-spacing: 0.05em;
        color: var(--color-primary);
        background: #f0fdf4;
        border: 1px solid rgba(5,150,105,0.2);
        padding: 0.2rem 0.625rem;
        border-radius: 2rem;
    }

    .art-tag-popular {
        color: #b45309;
        background: #fffbeb;
        border-color: rgba(180,83,9,0.2);
    }

    .art-tag-popular i { margin-right: 0.35rem; }

    .art-header h1 {
        font-family: 'Lora', Georgia, serif;
        font-size: clamp(1.5rem, 3vw, 2.125rem);
        font-weight: 600;
        color: var(--color-text-dark);
        line-height: 1.3;
        margin-bottom: 1rem;
    }

    .art-header-excerpt {
        font-size: 1.0625rem;
        color: var(--color-text-medium);
        line-height: 1.65;
        margin-bottom: 1.5rem;
    }

    .art-header-meta {
        display: flex;
        align-items: center;
        gap: 1.5rem;
        flex-wrap: wrap;
        padding-top: 1.25rem;
        border-top: 1px solid var(--color-border);
    }

    .art-meta-item {
        display: flex;
        align-items: center;
        gap: 0.375rem;
        font-size: 0.8125rem;
        color: var(--color-text-muted);
        font-weight: 500;
    }

    .art-meta-item svg { width: 0.9375rem; height: 0.9375rem; }

    /* ── Article body content ── */
    .art-body-card {
        background: var(--color-white);
        border: 1.5px solid var(--color-border);
        border-radius: var(--border-radius);
        padding: 2.5rem;
        margin-bottom: 1.5rem;
        animation: artIn 0.5s ease-out 0.1s both;
    }

    /* Typography for the article content */
    .art-content { font-family: 'DM Sans', sans-serif; }

    .art-content .art-section { margin-bottom: 2.5rem; }
    .art-content .art-section:last-child { margin-bottom: 0; }

    .art-content h2 {
        font-family: 'Lora', Georgia, serif;
        font-size: 1.375rem;
        font-weight: 600;
        color: var(--color-text-dark);
        margin-bottom: 1rem;
        padding-bottom: 0.625rem;
        border-bottom: 2px solid #f0fdf4;
        display: flex;
        align-items: center;
        gap: 0.5rem;
    }

    .art-content h2::before {
        content: '';
        display: block;
        width: 4px;
        height: 1.25rem;
        background: linear-gradient(180deg, var(--color-primary), #10b981);
        border-radius: 2px;
        flex-shrink: 0;
    }

    .art-content p {
        font-size: 1rem;
        color: var(--color-text-medium);
        line-height: 1.75;
        margin-bottom: 1rem;
    }

    .art-content p:last-child { margin-bottom: 0; }

    .art-content ul, .art-content ol {
        padding-left: 1.25rem;
        margin-bottom: 1rem;
        display: flex;
        flex-direction: column;
        gap: 0.5rem;
    }

    .art-content li {
        font-size: 1rem;
        color: var(--color-text-medium);
        line-height: 1.65;
    }

    .art-content strong { color: var(--color-text-dark); font-weight: 700; }
    .art-content em { font-style: italic; }

    .art-content code {
        font-family: 'Space Mono', monospace;
        font-size: 0.8125rem;
        background: #f0fdf4;
        color: var(--color-primary);
        padding: 0.15rem 0.4rem;
        border-radius: 4px;
        border: 1px solid rgba(5,150,105,0.15);
    }

    /* Callout / info box */
    .art-callout {
        background: #f0fdf4;
        border: 1px solid rgba(5,150,105,0.25);
        border-left: 4px solid var(--color-primary);
        border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
        padding: 1rem 1.25rem;
        margin: 1.25rem 0;
        display: flex;
        gap: 0.75rem;
        align-items: flex-start;
    }

    .art-callout-icon { font-size: 1.125rem; flex-shrink: 0; margin-top: 1px; }
    .art-callout-icon i { color: var(--color-primary); }

    .art-callout-text {
        font-size: 0.9rem;
        color: var(--color-text-medium);
        line-height: 1.6;
    }

    .art-callout-text strong { color: var(--color-text-dark); }

    /* Warning callout */
    .art-callout-warn {
        background: #fffbeb;
        border-color: rgba(245,158,11,0.25);
        border-left-color: #f59e0b;
    }

    .art-callout-warn .art-callout-icon i { color: #d97706; }

    /* ── Like / Dislike widget ── */
    .art-helpful-card {
        background: var(--color-white);
        border: 1.5px solid var(--color-border);
        border-radius: var(--border-radius);
        padding: 2rem 2.5rem;
        text-align: center;
        margin-bottom: 1.5rem;
        animation: artIn 0.5s ease-out 0.2s both;
    }

    .art-helpful-label {
        font-size: 1rem;
        font-weight: 700;
        color: var(--color-text-dark);
        margin-bottom: 0.375rem;
    }

    .art-helpful-sub {
        font-size: 0.875rem;
        color: var(--color-text-muted);
        margin-bottom: 1.5rem;
    }

    .art-helpful-actions {
        display: flex;
        justify-content: center;
        gap: 1rem;
        flex-wrap: wrap;
    }

    .art-helpful-btn {
        display: inline-flex;
        align-items: center;
        gap: 0.5rem;
        padding: 0.75rem 1.75rem;
        border-radius: var(--border-radius-sm);
        font-size: 0.9375rem;
        font-weight: 700;
        cursor: pointer;
        border: 2px solid var(--color-border);
        background: var(--color-white);
        color: var(--color-text-dark);
        font-family: 'DM Sans', sans-serif;
        transition: all 0.25s cubic-bezier(0.4,0,0.2,1);
        position: relative;
        overflow: hidden;
    }

    .art-helpful-btn svg { width: 1.25rem; height: 1.25rem; transition: transform 0.3s; }

    .art-helpful-btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }

    .art-helpful-btn-yes:hover {
        border-color: var(--color-primary);
        background: #f0fdf4;
        color: var(--color-primary);
    }

    .art-helpful-btn-yes:hover svg { transform: translateY(-3px); }

    .art-helpful-btn-no:hover {
        border-color: #ef4444;
        background: #fef2f2;
        color: #ef4444;
    }

    .art-helpful-btn-no:hover svg { transform: translateY(3px); }

    /* Voted states */
    .art-helpful-btn.voted-yes {
        border-color: var(--color-primary);
        background: linear-gradient(135deg, #f0fdf4, #ecfdf5);
        color: var(--color-primary);
        cursor: default;
        pointer-events: none;
    }

    .art-helpful-btn.voted-no {
        border-color: #ef4444;
        background: #fef2f2;
        color: #ef4444;
        cursor: default;
        pointer-events: none;
    }
    .art-helpful-btn.is-muted {
        opacity: 0.4;
        pointer-events: none;
    }

    .art-helpful-count {
        font-family: 'Space Mono', monospace;
        font-size: 0.75rem;
        background: var(--color-bg-light);
        padding: 0.1rem 0.45rem;
        border-radius: 2rem;
    }

    .art-helpful-thank {
        display: none;
        margin-top: 1.25rem;
        padding: 0.75rem 1.25rem;
        background: #f0fdf4;
        border: 1px solid rgba(5,150,105,0.2);
        border-radius: var(--border-radius-sm);
        font-size: 0.875rem;
        font-weight: 600;
        color: var(--color-primary);
        animation: thankIn 0.4s cubic-bezier(0.34,1.56,0.64,1) both;
    }

    @keyframes thankIn {
        from { opacity:0; transform: scale(0.92); }
        to   { opacity:1; transform: scale(1); }
    }

    /* ── Right sidebar ── */
    .art-sidebar { position: sticky; top: 5rem; display: flex; flex-direction: column; gap: 1.25rem; }

    .art-sidebar-card {
        background: var(--color-white);
        border: 1.5px solid var(--color-border);
        border-radius: var(--border-radius);
        padding: 1.5rem;
        transition: border-color 0.2s, box-shadow 0.2s;
    }

    .art-sidebar-card:hover { border-color: rgba(5,150,105,0.3); box-shadow: var(--shadow-green); }

    .art-sidebar-title {
        font-size: 0.6875rem;
        font-weight: 700;
        text-transform: uppercase;
        letter-spacing: 0.1em;
        color: var(--color-primary);
        margin-bottom: 1rem;
        display: flex;
        align-items: center;
        gap: 0.4rem;
    }

    /* Related articles */
    .art-related-list { display: flex; flex-direction: column; gap: 0; }

    .art-related-link {
        display: flex;
        align-items: flex-start;
        gap: 0.625rem;
        padding: 0.75rem 0;
        border-bottom: 1px solid var(--color-border);
        text-decoration: none;
        transition: all 0.2s;
    }

    .art-related-link:last-child { border-bottom: none; padding-bottom: 0; }

    .art-related-link:hover { padding-left: 4px; }

    .art-related-dot {
        width: 0.4rem;
        height: 0.4rem;
        background: var(--color-primary);
        border-radius: 50%;
        flex-shrink: 0;
        margin-top: 0.45rem;
    }

    .art-related-info {}

    .art-related-title {
        font-size: 0.8125rem;
        font-weight: 600;
        color: var(--color-text-dark);
        line-height: 1.4;
        margin-bottom: 0.2rem;
        transition: color 0.2s;
    }

    .art-related-link:hover .art-related-title { color: var(--color-primary); }

    .art-related-time {
        font-size: 0.6875rem;
        color: var(--color-text-muted);
        display: flex;
        align-items: center;
        gap: 0.25rem;
    }

    /* Share */
    .art-share-btns { display: flex; gap: 0.5rem; }

    .art-share-btn {
        flex: 1;
        padding: 0.55rem;
        border-radius: var(--border-radius-sm);
        border: 1.5px solid var(--color-border);
        background: var(--color-white);
        cursor: pointer;
        font-size: 0.8125rem;
        font-weight: 600;
        color: var(--color-text-medium);
        font-family: 'DM Sans', sans-serif;
        transition: all 0.2s;
        display: flex;
        align-items: center;
        justify-content: center;
        gap: 0.35rem;
        text-decoration: none;
    }

    .art-share-btn svg { width: 1rem; height: 1rem; }

    .art-share-btn:hover {
        border-color: var(--color-primary);
        background: #f0fdf4;
        color: var(--color-primary);
        transform: translateY(-1px);
    }
    .art-share-btn.is-copied {
        border-color: var(--color-primary);
        color: var(--color-primary);
    }

    /* Contact CTA in sidebar */
    .art-sidebar-cta {
        background: linear-gradient(135deg, var(--color-primary), #10b981);
        border: none;
        text-align: center;
        padding: 1.75rem 1.25rem;
    }

    .art-sidebar-cta:hover { box-shadow: var(--shadow-green); border-color: transparent; }

    .art-sidebar-cta-icon {
        font-size: 1.75rem;
        margin-bottom: 0.625rem;
    }

    .art-sidebar-cta h3 {
        font-size: 0.9375rem;
        font-weight: 700;
        color: white;
        margin-bottom: 0.4rem;
    }

    .art-sidebar-cta p {
        font-size: 0.8rem;
        color: rgba(255,255,255,0.85);
        margin-bottom: 1.1rem;
        line-height: 1.5;
    }

    .art-sidebar-cta a {
        display: inline-flex;
        align-items: center;
        gap: 0.4rem;
        padding: 0.55rem 1.25rem;
        background: white;
        color: var(--color-primary);
        border-radius: var(--border-radius-sm);
        font-size: 0.8125rem;
        font-weight: 700;
        text-decoration: none;
        transition: all 0.25s;
        box-shadow: var(--shadow-sm);
    }

    .art-sidebar-cta a:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); }

    /* ── Back to category ── */
    .art-back-link {
        display: inline-flex;
        align-items: center;
        gap: 0.5rem;
        font-size: 0.875rem;
        font-weight: 600;
        color: var(--color-text-muted);
        text-decoration: none;
        margin-bottom: 2rem;
        transition: color 0.2s;
    }

    .art-back-link svg { width: 1rem; height: 1rem; transition: transform 0.2s; }
    .art-back-link:hover { color: var(--color-primary); }
    .art-back-link:hover svg { transform: translateX(-3px); }

    /* ── Responsive ── */
    @media (max-width: 1060px) {
        .art-layout { grid-template-columns: 1fr 240px; }
        .art-toc { display: none; }
    }

    @media (max-width: 760px) {
        .art-layout { grid-template-columns: 1fr; padding: 1.5rem 1.25rem 4rem; gap: 1.5rem; }
        .art-sidebar { position: static; }
        .art-header, .art-body-card { padding: 1.5rem; }
        .art-helpful-card { padding: 1.5rem; }
        .art-breadcrumb-readtime { display: none; }
    }