/* ==========================================================================
   Long-form content: HLD/LLD design pages, concepts, guides.
   Reading experience first — generous measure, clear hierarchy, calm surfaces.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Page shell
   -------------------------------------------------------------------------- */
.page-layout {
    max-width: var(--measure);
    margin: 0 auto;
    padding: var(--sp-6) var(--sp-5) var(--sp-8);
    display: grid;
    grid-template-columns: minmax(0, 1fr) 232px;
    gap: var(--sp-7);
    position: relative;
    z-index: 1;
}
.page-layout.no-toc { grid-template-columns: minmax(0, 1fr); max-width: 900px; }

.content { min-width: 0; }

/* --------------------------------------------------------------------------
   Breadcrumbs
   -------------------------------------------------------------------------- */
.breadcrumbs {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.4rem;
    font-size: var(--fs-sm);
    color: var(--text-dim);
    margin-bottom: var(--sp-4);
}
.breadcrumbs a { color: var(--text-muted); text-decoration: none; }
.breadcrumbs a:hover { color: var(--accent); }
.breadcrumbs .sep { opacity: 0.5; }

/* --------------------------------------------------------------------------
   Table of contents
   -------------------------------------------------------------------------- */
.toc {
    position: sticky;
    top: calc(var(--header-h) + var(--sp-4));
    align-self: start;
    max-height: calc(100vh - var(--header-h) - var(--sp-6));
    overflow-y: auto;
    font-size: var(--fs-sm);
    padding-left: var(--sp-4);
    border-left: 1px solid var(--border);
}
.toc-title {
    font-size: var(--fs-xs);
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-dim);
    margin-bottom: var(--sp-3);
}
.toc a {
    display: block;
    padding: 0.3rem 0;
    color: var(--text-dim);
    text-decoration: none;
    line-height: 1.45;
    border: none;
    transition: color var(--dur-fast) var(--ease);
}
.toc a:hover { color: var(--text); }
.toc a.active { color: var(--accent); font-weight: 600; }
.toc a.toc-h3 { padding-left: var(--sp-3); font-size: var(--fs-xs); }

/* --------------------------------------------------------------------------
   Typography
   -------------------------------------------------------------------------- */
.content h1 {
    font-size: var(--fs-3xl);
    font-weight: 800;
    letter-spacing: -0.035em;
    line-height: 1.12;
    color: var(--text);
    margin-bottom: var(--sp-4);
    text-wrap: balance;
}
.content h2 {
    font-size: var(--fs-xl);
    font-weight: 700;
    letter-spacing: -0.02em;
    line-height: 1.25;
    color: var(--text);
    margin: var(--sp-7) 0 var(--sp-4);
    padding-bottom: var(--sp-3);
    border-bottom: 1px solid var(--border);
    text-wrap: balance;
}
.content h3 {
    font-size: var(--fs-lg);
    font-weight: 650;
    letter-spacing: -0.012em;
    color: var(--text);
    margin: var(--sp-6) 0 var(--sp-3);
}
.content h4 {
    font-size: var(--fs-md);
    font-weight: 600;
    color: var(--text);
    margin: var(--sp-5) 0 var(--sp-2);
}

.content p {
    margin-bottom: var(--sp-4);
    color: var(--text-muted);
    line-height: 1.75;
    max-width: 74ch;
}
.content strong { color: var(--text); font-weight: 650; }
.content em { color: var(--text-muted); }

.content a {
    color: var(--accent);
    text-decoration: underline;
    text-decoration-color: color-mix(in srgb, var(--accent) 35%, transparent);
    text-decoration-thickness: 1px;
    text-underline-offset: 0.18em;
    transition: color var(--dur-fast) var(--ease), text-decoration-color var(--dur-fast) var(--ease);
}
.content a:hover { color: var(--accent-hover); text-decoration-color: currentColor; }

.content ul, .content ol {
    margin-bottom: var(--sp-4);
    padding-left: var(--sp-5);
    color: var(--text-muted);
    max-width: 74ch;
}
.content li { margin-bottom: 0.4rem; line-height: 1.72; }
.content li::marker { color: var(--text-dim); }

.content hr {
    border: none;
    height: 1px;
    background: var(--border);
    margin: var(--sp-7) 0;
}

/* --------------------------------------------------------------------------
   Code
   -------------------------------------------------------------------------- */
.content code {
    font-family: var(--font-mono);
    font-size: 0.855em;
    padding: 0.12em 0.4em;
    border-radius: var(--r-xs);
    background: var(--surface-2);
    border: 1px solid var(--border);
    color: var(--accent);
    word-break: break-word;
}
[data-theme="light"] .content code { color: #4338ca; }

/* Disable programming ligatures so != renders literally, not as ≠ */
.content code,
.content pre,
.content pre code,
pre[class*="language-"],
code[class*="language-"] {
    font-variant-ligatures: none !important;
    font-feature-settings: "liga" 0, "calt" 0 !important;
}

.content pre {
    position: relative;
    background: var(--bg-subtle);
    border: 1px solid var(--border);
    border-radius: var(--r-md);
    padding: var(--sp-4);
    overflow-x: auto;
    margin-bottom: var(--sp-5);
    -webkit-overflow-scrolling: touch;
}
.content pre code {
    background: none !important;
    border: none !important;
    padding: 0 !important;
    font-size: var(--fs-sm);
    color: var(--text) !important;
    line-height: 1.65;
}

/* Copy button — always present on touch, hover-revealed on pointer devices */
.copy-btn {
    position: absolute;
    top: 8px;
    right: 8px;
    padding: 0.25rem 0.6rem;
    font-size: var(--fs-xs);
    font-weight: 600;
    color: var(--text-muted);
    background: var(--surface-2);
    border: 1px solid var(--border);
    border-radius: var(--r-xs);
    cursor: pointer;
    opacity: 1;
    transition: opacity var(--dur) var(--ease), color var(--dur-fast) var(--ease),
                border-color var(--dur-fast) var(--ease);
}
.copy-btn:hover { color: var(--accent); border-color: var(--border-accent); }
.copy-btn.copied { color: var(--success); border-color: var(--success); }

@media (hover: hover) and (pointer: fine) {
    .copy-btn { opacity: 0; }
    .content pre:hover .copy-btn,
    .copy-btn:focus-visible { opacity: 1; }
}

.code-lang-badge {
    position: absolute;
    top: 8px;
    left: 12px;
    font-size: 0.6rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    color: var(--text-dim);
}

/* Tabbed code blocks */
.code-tabs {
    margin-bottom: var(--sp-5);
    border: 1px solid var(--border);
    border-radius: var(--r-md);
    overflow: hidden;
    background: var(--bg-subtle);
}
.code-tabs .tab-buttons {
    display: flex;
    overflow-x: auto;
    background: var(--surface-2);
    border-bottom: 1px solid var(--border);
    scrollbar-width: none;
}
.code-tabs .tab-buttons::-webkit-scrollbar { display: none; }
.code-tabs .tab-btn {
    padding: 0.55rem 1rem;
    font-size: var(--fs-sm);
    font-weight: 600;
    color: var(--text-dim);
    border-bottom: 2px solid transparent;
    white-space: nowrap;
    min-height: 40px;
    transition: color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.code-tabs .tab-btn:hover { color: var(--text); }
.code-tabs .tab-btn.active { color: var(--accent); border-bottom-color: var(--accent); }
.code-tabs .tab-content { display: none; }
.code-tabs .tab-content.active { display: block; }
.code-tabs .tab-content pre { border: none; border-radius: 0; margin: 0; }

/* Prism token colours — WCAG-checked against --bg-subtle */
pre[class*="language-"],
code[class*="language-"] {
    font-family: var(--font-mono) !important;
    font-size: var(--fs-sm) !important;
    text-shadow: none !important;
}
pre[class*="language-"] {
    background: var(--bg-subtle) !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--r-md) !important;
    padding: var(--sp-4) !important;
}
.token.comment, .token.prolog, .token.cdata { color: #8b90a0 !important; }
.token.keyword, .token.class-name { color: #c4b5fd !important; }
.token.string, .token.char { color: #86efac !important; }
.token.function { color: #93c5fd !important; }
.token.number, .token.boolean { color: #fcd34d !important; }
.token.operator, .token.punctuation { color: #b0b4c0 !important; }
.token.annotation { color: #a78bfa !important; }

[data-theme="light"] .token.comment,
[data-theme="light"] .token.prolog,
[data-theme="light"] .token.cdata { color: #64748b !important; }
[data-theme="light"] .token.keyword,
[data-theme="light"] .token.class-name { color: #7c3aed !important; }
[data-theme="light"] .token.string,
[data-theme="light"] .token.char { color: #047857 !important; }
[data-theme="light"] .token.function { color: #1d4ed8 !important; }
[data-theme="light"] .token.number,
[data-theme="light"] .token.boolean { color: #b45309 !important; }
[data-theme="light"] .token.operator,
[data-theme="light"] .token.punctuation { color: #475569 !important; }

/* --------------------------------------------------------------------------
   Tables — scroll-hinted on mobile
   -------------------------------------------------------------------------- */
.content .table-scroll {
    overflow-x: auto;
    margin-bottom: var(--sp-5);
    border: 1px solid var(--border);
    border-radius: var(--r-md);
    -webkit-overflow-scrolling: touch;
}
.content .table-scroll table {
    margin: 0;
    border: none;
    border-radius: 0;
    display: table;
    width: 100%;
}
.content table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin-bottom: var(--sp-5);
    font-size: var(--fs-sm);
    display: block;
    overflow-x: auto;
    border: 1px solid var(--border);
    border-radius: var(--r-md);
}
.content th {
    position: sticky;
    top: 0;
    background: var(--surface-2);
    color: var(--text);
    padding: 0.7rem 0.9rem;
    text-align: left;
    font-weight: 700;
    font-size: var(--fs-xs);
    letter-spacing: 0.02em;
    text-transform: uppercase;
    border-bottom: 1px solid var(--border);
    white-space: nowrap;
}
.content td {
    padding: 0.7rem 0.9rem;
    border-bottom: 1px solid var(--border);
    color: var(--text-muted);
    vertical-align: top;
}
.content tbody tr:last-child td { border-bottom: none; }
.content tbody tr:hover td { background: var(--surface-2); }

/* --------------------------------------------------------------------------
   Callouts
   -------------------------------------------------------------------------- */
.content blockquote {
    padding: var(--sp-4);
    margin-bottom: var(--sp-4);
    background: var(--surface);
    border: 1px solid var(--border);
    border-left: 3px solid var(--accent);
    border-radius: var(--r-sm);
}
.content blockquote p { margin-bottom: 0; color: var(--text-muted); }
.content blockquote p + p { margin-top: var(--sp-3); }

.hint-block {
    display: block;
    margin-top: var(--sp-2);
    padding: var(--sp-3) var(--sp-4);
    background: var(--accent-subtle);
    border: 1px solid var(--border-accent);
    border-radius: var(--r-sm);
    font-size: var(--fs-sm);
    color: var(--text-muted);
    line-height: 1.65;
}

/* --------------------------------------------------------------------------
   Diagrams
   -------------------------------------------------------------------------- */
.mermaid,
.excalidraw-diagram {
    background: var(--bg-subtle);
    border: 1px solid var(--border);
    border-radius: var(--r-md);
    padding: var(--sp-5);
    margin-bottom: var(--sp-5);
    text-align: center;
    overflow-x: auto;
    max-width: 100%;
    -webkit-overflow-scrolling: touch;
}
.excalidraw-diagram img { display: inline-block; }
[data-theme="dark"] .excalidraw-diagram img {
    filter: invert(0.88) hue-rotate(180deg) saturate(1.6) brightness(1.1);
}

/* --------------------------------------------------------------------------
   Deep dives (Bad / Good / Great)
   -------------------------------------------------------------------------- */
.deep-dive-section { margin-bottom: var(--sp-6); }
.deep-dive-section > h3 {
    margin: 0 0 var(--sp-3);
    padding: 0.6rem var(--sp-4);
    font-size: var(--fs-md);
    background: var(--surface-2);
    border-left: 3px solid var(--accent);
    border-radius: 0 var(--r-sm) var(--r-sm) 0;
}

.deep-dive-tabs {
    display: flex;
    gap: 0;
    overflow-x: auto;
    border-bottom: 1px solid var(--border);
    scrollbar-width: none;
}
.deep-dive-tabs::-webkit-scrollbar { display: none; }
.deep-dive-tab {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.55rem 1rem;
    font-size: var(--fs-sm);
    font-weight: 600;
    color: var(--text-dim);
    border-bottom: 2px solid transparent;
    white-space: nowrap;
    min-height: 42px;
    transition: color var(--dur-fast) var(--ease), border-color var(--dur-fast) var(--ease);
}
.deep-dive-tab:hover { color: var(--text-muted); }
.deep-dive-tab.active { color: var(--text); border-bottom-color: var(--accent); }
.deep-dive-tab .tab-dot { width: 7px; height: 7px; border-radius: 50%; flex-shrink: 0; }
.deep-dive-tab .tab-dot.dot-bad { background: var(--danger); }
.deep-dive-tab .tab-dot.dot-good { background: var(--warning); }
.deep-dive-tab .tab-dot.dot-great { background: var(--success); }

.deep-dive-panel { display: none; padding: var(--sp-4) 0; }
.deep-dive-panel.active { display: block; }
.deep-dive-panel[data-level="bad"] { border-left: 3px solid var(--danger); padding-left: var(--sp-4); }
.deep-dive-panel[data-level="good"] { border-left: 3px solid var(--warning); padding-left: var(--sp-4); }
.deep-dive-panel[data-level="great"] { border-left: 3px solid var(--success); padding-left: var(--sp-4); }

/* --------------------------------------------------------------------------
   "Simulate this design" CTA (injected by JS on HLD pages)
   Selector is .content a.sim-design-btn so it outranks the generic `.content a`
   link colour — otherwise the label renders accent-on-accent and disappears.
   Kept visible on mobile: the simulator is one of the best features here.
   -------------------------------------------------------------------------- */
.content a.sim-design-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    margin: 0 0 var(--sp-5);
    padding: 0.65rem 1.15rem;
    min-height: 42px;
    font-size: var(--fs-sm);
    font-weight: 600;
    color: var(--accent-contrast);
    background: var(--accent);
    border: 1px solid var(--accent);
    border-radius: var(--r-sm);
    text-decoration: none;
    transition: background var(--dur-fast) var(--ease), box-shadow var(--dur-fast) var(--ease),
                transform var(--dur-fast) var(--ease);
}
.content a.sim-design-btn:hover {
    color: var(--accent-contrast);
    background: var(--accent-hover);
    border-color: var(--accent-hover);
    box-shadow: var(--shadow-accent);
    transform: translateY(-1px);
}

/* --------------------------------------------------------------------------
   Author byline
   -------------------------------------------------------------------------- */
.author-byline {
    display: flex;
    gap: var(--sp-4);
    align-items: flex-start;
    margin-top: var(--sp-7);
    padding: var(--sp-4);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--r-lg);
}
.author-byline-avatar { border-radius: 50%; flex-shrink: 0; border: 1px solid var(--border); }
.author-byline-body { min-width: 0; }
.author-byline-label {
    display: block;
    font-size: var(--fs-xs);
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-dim);
}
.author-byline-name { font-size: var(--fs-md); font-weight: 700; color: var(--text); text-decoration: none; }
.author-byline-name:hover { color: var(--accent); }
.author-byline-title { color: var(--text-muted); font-size: var(--fs-sm); margin-left: 0.4rem; }
.author-byline-bio { color: var(--text-muted); font-size: var(--fs-sm); line-height: 1.6; margin: var(--sp-2) 0 0; }

/* --------------------------------------------------------------------------
   Mobile TOC drawer
   -------------------------------------------------------------------------- */
.mobile-toc-btn {
    display: none;
    position: fixed;
    bottom: var(--sp-5);
    left: var(--sp-5);
    align-items: center;
    gap: 0.4rem;
    padding: 0.6rem 1.1rem;
    min-height: 44px;
    font-size: var(--fs-sm);
    font-weight: 600;
    color: var(--text-muted);
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--r-full);
    box-shadow: var(--shadow-md);
    z-index: 50;
}
.mobile-toc-btn:hover { color: var(--accent); border-color: var(--border-accent); }

.mobile-toc-drawer {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    max-height: 62vh;
    overflow-y: auto;
    padding: var(--sp-5) var(--sp-5) var(--sp-6);
    background: var(--surface);
    border-top: 1px solid var(--border);
    border-radius: var(--r-xl) var(--r-xl) 0 0;
    box-shadow: var(--shadow-lg);
    z-index: 200;
}
.mobile-toc-drawer.open { display: block; animation: drawerIn var(--dur) var(--ease) both; }
.mobile-toc-drawer a {
    display: block;
    padding: 0.7rem 0;
    min-height: 44px;
    color: var(--text-muted);
    text-decoration: none;
    font-size: var(--fs-base);
    border-bottom: 1px solid var(--border);
}
.mobile-toc-drawer a:last-child { border-bottom: none; }
.mobile-toc-drawer a.toc-h3 { padding-left: var(--sp-4); font-size: var(--fs-sm); }

@keyframes drawerIn {
    from { transform: translateY(100%); }
    to { transform: translateY(0); }
}

.mobile-toc-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.55);
    z-index: 199;
}
.mobile-toc-overlay.open { display: block; }

/* --------------------------------------------------------------------------
   Support / donate strip
   -------------------------------------------------------------------------- */
.support-strip {
    max-width: var(--measure-narrow);
    margin: var(--sp-7) auto 0;
    padding: var(--sp-5);
    text-align: center;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--r-lg);
    position: relative;
    z-index: 1;
}
.support-strip p { color: var(--text-muted); font-size: var(--fs-sm); margin-bottom: var(--sp-3); }

/* --------------------------------------------------------------------------
   Responsive
   -------------------------------------------------------------------------- */
@media (max-width: 1024px) {
    .page-layout { grid-template-columns: minmax(0, 1fr); gap: var(--sp-5); }
    .toc { display: none; }
    .mobile-toc-btn { display: inline-flex; }
}

@media (max-width: 640px) {
    .page-layout { padding: var(--sp-5) var(--sp-4) var(--sp-8); }
    .content pre { padding: var(--sp-3); border-radius: var(--r-sm); }
    .content p, .content ul, .content ol { max-width: none; }
    .mermaid, .excalidraw-diagram { padding: var(--sp-3); }
    .author-byline { flex-direction: column; gap: var(--sp-3); }
    /* Keep floating controls from colliding on narrow screens */
    .mobile-toc-btn { left: var(--sp-4); bottom: var(--sp-4); }
    #back-to-top { right: var(--sp-4); bottom: var(--sp-4); }
}

/* --------------------------------------------------------------------------
   Practice loop — read the design -> build it in the simulator -> draw it
   Appended after the article body on every HLD design page.
   -------------------------------------------------------------------------- */
.practice-loop {
    margin: var(--sp-7) 0 var(--sp-6);
    padding: var(--sp-5);
    border: 1px solid var(--border);
    border-radius: var(--r-lg);
    background:
        radial-gradient(120% 140% at 0% 0%, var(--accent-subtle), transparent 60%),
        var(--surface);
}
.practice-loop-head h2 {
    font-size: var(--fs-lg);
    font-weight: 750;
    letter-spacing: -0.02em;
    margin: 0 0 6px;
    /* Override the heading rules the article body sets (anchor offsets, rules) */
    border: none;
    padding: 0;
}
.practice-loop-head p { color: var(--text-muted); margin: 0 0 var(--sp-4); line-height: 1.6; }

.practice-loop-steps { display: grid; gap: var(--sp-2); }

.pl-step {
    display: flex;
    align-items: flex-start;
    gap: var(--sp-3);
    padding: var(--sp-3) var(--sp-4);
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--r-md);
    text-decoration: none;
}
.pl-num {
    flex-shrink: 0;
    width: 24px;
    height: 24px;
    display: grid;
    place-items: center;
    border-radius: var(--r-full);
    background: var(--surface-3);
    color: var(--text-dim);
    font-size: var(--fs-xs);
    font-weight: 700;
    font-variant-numeric: tabular-nums;
}
.pl-body { display: flex; flex-direction: column; gap: 3px; min-width: 0; }
.pl-body strong { font-weight: 650; color: var(--text); font-size: var(--fs-base); }
.pl-body span { color: var(--text-muted); font-size: var(--fs-sm); line-height: 1.55; }
.pl-tag {
    display: inline-block;
    margin-left: 6px;
    padding: 1px 7px;
    border-radius: var(--r-full);
    background: var(--accent-subtle);
    color: var(--accent);
    font-size: 0.66rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    vertical-align: 1px;
}
.pl-go {
    margin-left: auto;
    align-self: center;
    flex-shrink: 0;
    color: var(--accent);
    font-size: var(--fs-md);
    transition: transform var(--dur-fast) var(--ease);
}

/* Step 1 is the page you're already on — present, but visibly inert. */
.pl-step-done { opacity: 0.72; }
.pl-step-done .pl-num { background: var(--accent-subtle); color: var(--accent); }

/* The band renders inside .content, and `.content a` (0,1,1) out-specifies
   `.pl-step` (0,1,0) — so without this the whole card, body copy included, gets
   the article link underline. These selectors clear 0,2,0. */
.content .pl-step-link,
.content .pl-step-link:hover { text-decoration: none; color: inherit; }
.pl-step-link { transition: border-color var(--dur-fast) var(--ease), background var(--dur-fast) var(--ease); }
.pl-step-link:hover { border-color: var(--accent); background: var(--surface-2); }
.pl-step-link:hover .pl-num { background: var(--accent); color: var(--accent-contrast); }
.pl-step-link:hover .pl-go { transform: translateX(3px); }

@media (max-width: 600px) {
    .practice-loop { padding: var(--sp-4); margin: var(--sp-6) 0 var(--sp-5); }
    .pl-step { padding: var(--sp-3); }
    .pl-go { display: none; }
}