:root {
    color-scheme: light dark;
    --bg: #f3f0e6;
    --paper: #fffdf7;
    --ink: #16201d;
    --muted: #5c655f;
    --line: #d7d0bd;
    --line-strong: #b7ac8e;
    --soft: #ece5d2;
    --accent: #1d4d8f;
    --accent-strong: #123568;
    --accent-soft: #dde6f2;
    --rust: #a3521c;
    --rust-strong: #7c3d12;
    --warn: #9a5b0a;
    --warn-strong: #7a4506;
    --warn-bg: #f3e6d2;
    --terminal-bg: #e4e1d6;
    --terminal-ink: #40473f;
    --code: #10171f;
    --code-ink: #e9f0f6;
    --shadow: 6px 6px 0 0 color-mix(in srgb, var(--ink) 12%, transparent);
    --sidebar: 19rem;
    --grid: color-mix(in srgb, var(--line) 55%, transparent);
    font-family: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Noto Serif TC", ui-sans-serif, system-ui, sans-serif;
    font-synthesis: none;
}

/* OS 暗色偏好：純 CSS 就生效，不等 JavaScript，避免換頁白色閃爍。明確選擇 light 時不套用。 */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        color-scheme: dark;
        --bg: #10161a;
        --paper: #161f24;
        --ink: #eef2ee;
        --muted: #a2ada9;
        --line: #2d3a3f;
        --line-strong: #46595f;
        --soft: #1e2a2f;
        --accent: #79a8e8;
        --accent-strong: #a9c9f5;
        --accent-soft: #1c2c40;
        --rust: #e0965a;
        --rust-strong: #f0b57f;
        --warn: #f0b444;
        --warn-strong: #ffd27a;
        --warn-bg: #3a2f16;
        --terminal-bg: #333d38;
        --terminal-ink: #d8ded9;
        --code: #0a1016;
        --code-ink: #e5eef4;
        --shadow: 6px 6px 0 0 color-mix(in srgb, black 55%, transparent);
        --grid: color-mix(in srgb, var(--line) 65%, transparent);
    }
}

[data-theme="light"] { color-scheme: light; }

[data-theme="dark"] {
    color-scheme: dark;
    --bg: #10161a;
    --paper: #161f24;
    --ink: #eef2ee;
    --muted: #a2ada9;
    --line: #2d3a3f;
    --line-strong: #46595f;
    --soft: #1e2a2f;
    --accent: #79a8e8;
    --accent-strong: #a9c9f5;
    --accent-soft: #1c2c40;
    --rust: #e0965a;
    --rust-strong: #f0b57f;
    --warn: #f0b444;
    --warn-strong: #ffd27a;
    --warn-bg: #3a2f16;
    --terminal-bg: #333d38;
    --terminal-ink: #d8ded9;
    --code: #0a1016;
    --code-ink: #e5eef4;
    --shadow: 6px 6px 0 0 color-mix(in srgb, black 55%, transparent);
    --grid: color-mix(in srgb, var(--line) 65%, transparent);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 5rem; overflow-x: clip; }
body {
    margin: 0;
    background-color: var(--bg);
    background-image:
        linear-gradient(var(--grid) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid) 1px, transparent 1px);
    background-size: 28px 28px;
    color: var(--ink);
    line-height: 1.75;
    letter-spacing: 0.08em;
}
::selection { background: var(--accent); color: var(--paper); }
a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: .2em; }
a:hover { color: var(--accent-strong); }
button, input { font: inherit; }
button { color: inherit; }
:focus-visible { outline: 3px solid var(--rust); outline-offset: 3px; }

.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 100; padding: .65rem 1rem; background: var(--ink); color: var(--paper); }
.skip-link:focus { top: 1rem; }

.topbar { position: fixed; inset: 0 0 auto 0; height: 3.75rem; z-index: 30; display: flex; align-items: center; gap: .75rem; padding: 0 1rem; background: color-mix(in srgb, var(--paper) 94%, transparent); border-bottom: 2px solid var(--ink); backdrop-filter: blur(16px); }
.brand { display: flex; align-items: baseline; gap: .55rem; color: var(--ink); text-decoration: none; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-weight: 700; letter-spacing: -.01em; }
.brand::before { content: "["; color: var(--rust); font-weight: 700; }
.brand span::after { content: "]"; color: var(--rust); font-weight: 700; margin-left: .05em; }
.brand small { color: var(--muted); font-size: .68rem; letter-spacing: .02em; font-family: "Iowan Old Style", Georgia, "Noto Serif TC", serif; font-style: italic; }
.topbar-spacer { flex: 1; }
.icon-button { display: inline-grid; place-items: center; min-width: 2.35rem; min-height: 2.35rem; border: 1px solid transparent; border-radius: 999px; background: transparent; color: var(--muted); cursor: pointer; transition: border-color 160ms ease-out, background 160ms ease-out, color 160ms ease-out, transform 100ms ease-out; }
.icon-button:hover { background: var(--accent-soft); border-color: var(--line-strong); color: var(--accent-strong); }
.icon-button:active { transform: scale(.94); }
.icon-button svg { display: block; }
.menu-button { display: none; }
.theme-button .icon-sun { display: none; }
.theme-button .icon-moon { display: block; }
.theme-button[data-active-theme="dark"] .icon-sun { display: block; }
.theme-button[data-active-theme="dark"] .icon-moon { display: none; }
.theme-button svg { transition: transform 220ms cubic-bezier(.34, 1.56, .64, 1), opacity 160ms ease-out; }
.theme-button:hover svg { transform: rotate(-14deg) scale(1.08); }
.progress-line { position: absolute; left: 0; bottom: -2px; width: 100%; height: 3px; appearance: none; border: 0; background: transparent; }
.progress-line::-webkit-progress-bar { background: transparent; }
.progress-line::-webkit-progress-value { background: var(--rust); }
.progress-line::-moz-progress-bar { background: var(--rust); }

.sidebar { position: fixed; inset: 3.75rem auto 0 0; width: var(--sidebar); padding: 1.25rem 1rem 2rem; overflow: auto; border-right: 2px solid var(--ink); background: var(--paper); z-index: 20; scrollbar-width: thin; scrollbar-color: var(--line-strong) transparent; }
.sidebar::-webkit-scrollbar { width: 8px; }
.sidebar::-webkit-scrollbar-track { background: transparent; }
.sidebar::-webkit-scrollbar-thumb { background: var(--line-strong); border-radius: 999px; border: 2px solid var(--paper); }
.sidebar::-webkit-scrollbar-thumb:hover { background: var(--muted); }
.nav-part { margin: 1.35rem .5rem .4rem; color: var(--accent-strong); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .7rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.chapter-nav { list-style: none; margin: 0; padding: 0; }
.chapter-nav a { display: grid; grid-template-columns: 1.9rem 1fr; gap: .5rem; padding: .5rem .55rem; border-left: 3px solid transparent; color: var(--muted); text-decoration: none; line-height: 1.35; transition: border-color 140ms ease-out, background 140ms ease-out; }
.chapter-nav a:hover { background: var(--soft); color: var(--ink); border-left-color: var(--line-strong); }
.chapter-nav a[aria-current="page"] { background: var(--accent-soft); color: var(--accent-strong); font-weight: 700; border-left-color: var(--rust); }
.chapter-number { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-variant-numeric: tabular-nums; color: var(--muted); }
.shell { padding: 5.25rem 1.5rem 4rem calc(var(--sidebar) + 1.5rem); }
.reader { width: min(100%, 52rem); margin: 0 auto; }
.article { position: relative; padding: clamp(1.5rem, 4vw, 3.8rem); background: var(--paper); border: 2px solid var(--ink); box-shadow: var(--shadow); }
.article::before {
    content: "";
    position: absolute;
    inset: .5rem;
    border: 1px solid var(--line-strong);
    pointer-events: none;
}
.eyebrow { margin: 0 0 .5rem; color: var(--rust); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
h1 { margin: 0; max-width: 15ch; font-family: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Noto Serif TC", serif; font-weight: 700; font-size: clamp(2.25rem, 6vw, 4.6rem); line-height: 1.05; letter-spacing: .02em; }
.article h1 { font-size: clamp(2rem, 5vw, 3.45rem); }
.deck { max-width: 44rem; color: var(--muted); font-size: clamp(1.05rem, 2vw, 1.25rem); }
.meta { display: flex; flex-wrap: wrap; gap: 1rem; margin: 1rem 0 2.4rem; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .78rem; }
.lead { margin: 0 0 2.2rem; padding-bottom: 2rem; border-bottom: 2px solid var(--ink); font-size: 1.18rem; line-height: 1.8; }
h2 { margin: 5rem 0 1.15rem; font-family: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Noto Serif TC", serif; font-weight: 700; font-size: 1.7rem; line-height: 1.25; letter-spacing: .02em; }
h2::before { content: "§ "; color: var(--rust); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
h3 { margin: 2rem 0 .65rem; font-size: 1.15rem; font-weight: 700; letter-spacing: .02em; }
p, li { max-width: 45rem; letter-spacing: .08em; }
li + li { margin-top: .35rem; }
blockquote { margin: 1.5rem 0; padding: .6rem 1rem; color: var(--muted); border-left: 3px solid var(--rust); background: var(--bg); font-style: italic; }

pre { position: relative; margin: 1.4rem 0; padding: 2.35rem 1.15rem 1.15rem; overflow: auto; color: var(--code-ink); background: var(--code); border: 1px solid var(--line-strong); border-radius: 0; line-height: 1.55; tab-size: 4; }
pre::before { content: attr(data-lang); position: absolute; top: .62rem; left: 1.15rem; color: #82918c; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .68rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; }
code { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .9em; }
pre code { display: block; letter-spacing: normal; }
:not(pre) > code { padding: .1em .32em; background: var(--soft); border: 1px solid var(--line); border-radius: 0; }
.hljs-comment, .hljs-quote { color: #7f918b; font-style: italic; }
.hljs-keyword, .hljs-selector-tag, .hljs-literal, .hljs-section { color: #ff8f70; }
.hljs-string, .hljs-attr, .hljs-template-variable, .hljs-addition { color: #9ed88f; }
.hljs-number, .hljs-symbol, .hljs-bullet, .hljs-variable, .hljs-regexp { color: #e9bd75; }
.hljs-title, .hljs-title.function_, .hljs-title.class_, .hljs-function .hljs-title { color: #82c7ff; }
.hljs-built_in, .hljs-type, .hljs-name { color: #7bd8ce; }
.hljs-params, .hljs-property, .hljs-attribute { color: #d7e3de; }
.hljs-meta, .hljs-doctag { color: #c4a7e7; }
.hljs-deletion { color: #ff7b72; background: rgb(255 123 114 / .1); }
.hljs-addition { background: rgb(158 216 143 / .08); }
.copy-button { position: absolute; top: .55rem; right: .55rem; padding: .28rem .5rem; border: 1px solid #4b5a54; border-radius: 0; background: #26332e; color: #dce8e3; cursor: pointer; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .72rem; }
.copy-button:active { transform: translate(1px, 1px); }

table { display: block; width: 100%; margin: 1.5rem 0; overflow-x: auto; border-collapse: collapse; border: 1px solid var(--line-strong); }
th, td { padding: .65rem .75rem; text-align: left; vertical-align: top; border-bottom: 1px solid var(--line); }
th { font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .78rem; color: var(--accent-strong); background: var(--soft); letter-spacing: .02em; }
.compare { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.compare section { padding: 1rem 1.1rem; border: 1px solid var(--line-strong); background: var(--bg); }
.compare h3 { margin-top: 0; }
.note { position: relative; margin: 1.7rem 0; padding: 1rem 1.1rem 1rem 1.4rem; border: 1px dashed var(--line-strong); background: var(--bg); }
.note::before { content: ""; position: absolute; left: 0; top: .35rem; bottom: .35rem; width: 4px; background: var(--rust); }
.note > strong { display: block; margin-bottom: .35rem; color: var(--rust-strong); }

details.reading-branch { margin: 1.6rem 0; padding: 1rem 1.1rem; border: 1px dashed var(--line-strong); background: var(--bg); }
details.reading-branch > summary { cursor: pointer; font-weight: 700; }
details.reading-branch[open] > summary { margin-bottom: .75rem; }

figure.step-flow, figure.decision-tree { margin: 1.6rem 0; }
figure.step-flow figcaption, figure.decision-tree figcaption { margin-top: .6rem; color: var(--muted); font-size: .85rem; font-style: italic; }
.video-embed { margin: 1.6rem 0; }
.video-embed iframe { display: block; width: 100%; height: auto; aspect-ratio: 16 / 9; border: 2px solid var(--ink); background: var(--code); }
.video-embed figcaption { margin-top: .6rem; color: var(--muted); font-size: .85rem; font-style: italic; }

.step-flow ol { display: flex; flex-wrap: wrap; align-items: stretch; gap: .5rem; list-style: none; margin: 0; padding: 0; }
.step-flow li { display: grid; place-items: center; gap: .3rem; padding: .75rem 1rem; border: 1px solid var(--line-strong); background: var(--bg); text-align: center; }
.step-flow .step-label { font-weight: 700; }
.step-flow .crash-note { margin: 0; color: var(--muted); font-size: .82rem; font-weight: 400; }
.step-flow .step-arrow, .step-flow .step-loop-back { border: 0; background: transparent; color: var(--muted); padding: 0 .25rem; }
.step-flow .step-decision { min-width: 13rem; }
.step-flow .step-decision span { display: block; }
.step-flow .step-exit { color: var(--muted); font-size: .82rem; font-weight: 400; }
.step-flow .step-continue { color: var(--accent-strong); font-size: .82rem; font-weight: 700; }
.step-flow .step-loop-back { width: 100%; text-align: left; color: var(--rust-strong); font-weight: 700; }
.step-flow .step-here { color: var(--accent-strong); border-color: var(--accent); border-width: 2px; }

.decision-tree { padding: 1.1rem 1.2rem 1.3rem; border: 1px solid var(--line-strong); background: var(--paper); }
.decision-tree > ol { border-left: 0; padding-left: 0; margin: 0; }
.decision-tree ol ol, .decision-tree ol ul { border-left: 2px solid var(--line-strong); padding-left: 1.25rem; margin: .5rem 0 .5rem .5rem; }
.decision-tree li { margin: .35rem 0; }
.decision-tree > ol > li { padding-top: .9rem; border-top: 1px dashed var(--line-strong); }
.decision-tree > ol > li:first-child { padding-top: 0; border-top: 0; }
.decision-tree .gate { font-weight: 700; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.decision-tree-legend { display: flex; flex-wrap: wrap; gap: .5rem .75rem; margin: 0 0 1.1rem; padding: .7rem .9rem; border: 1px solid var(--line-strong); background: var(--bg); font-size: .82rem; }
.decision-tree-legend .outcome { margin: 0; }
.decision-tree .outcome {
    display: inline-block;
    margin-top: .2rem;
    padding: .1rem .55rem;
    border-radius: 0;
    font-weight: 700;
    font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    font-size: .85em;
    background: var(--accent-soft);
    color: var(--accent-strong);
}
.decision-tree .outcome::before { content: "▶ "; }
.decision-tree .outcome.blocked { background: var(--warn-bg); color: var(--warn-strong); }
.decision-tree .outcome.blocked::before { content: "⏸ "; }
.decision-tree .outcome.terminal { background: var(--terminal-bg); color: var(--terminal-ink); }
.decision-tree .outcome.terminal::before { content: "■ "; }

.chapter-toc { display: flex; flex-wrap: wrap; gap: .5rem; margin: 0 0 2.2rem; padding: 1rem 1.1rem; border: 1px solid var(--line-strong); background: var(--bg); }
.chapter-toc-label { flex-basis: 100%; margin: 0 0 .15rem; color: var(--accent-strong); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .7rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.chapter-toc a { padding: .3rem .6rem; border: 1px solid var(--line-strong); border-radius: 999px; background: var(--paper); color: var(--ink); font-size: .82rem; text-decoration: none; }
.chapter-toc a:hover { border-color: var(--rust); color: var(--rust-strong); }

.takeaways { margin: 0 0 2.2rem; padding: 1.1rem 1.2rem; border: 2px solid var(--accent); background: var(--accent-soft); }
.takeaways-label { margin: 0 0 .55rem; color: var(--accent-strong); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; }
.takeaways ul { margin: 0; padding-left: 1.2rem; }
.takeaways li { margin: 0; }
.takeaways li + li { margin-top: .4rem; }

.bridge, .closure { display: block; margin: 2.4rem 0 0; padding: 1.1rem 1.2rem; border-left: 4px solid var(--rust); background: var(--soft); font-size: 1.02rem; }
.bridge::before { content: "下一章進度："; display: block; margin-bottom: .3rem; color: var(--rust-strong); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .72rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.closure { text-align: center; font-weight: 700; font-size: 1.1rem; border-left: 0; border-top: 2px solid var(--ink); border-bottom: 2px solid var(--ink); background: transparent; }

.deep-interface-callback, .three-interfaces-summary, .four-outcomes, .responsibility-backref, .transition { display: block; margin: 1.7rem 0; padding: .9rem 1.1rem; border: 1px dashed var(--line-strong); background: var(--bg); color: var(--ink); font-size: .95rem; }
.deep-interface-callback::before, .three-interfaces-summary::before { content: "🔁 重複出現的形狀"; display: block; margin-bottom: .35rem; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .7rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.four-outcomes::before { content: "先看結論"; display: block; margin-bottom: .35rem; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .7rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }
.responsibility-backref::before, .transition::before { content: "回頭看"; display: block; margin-bottom: .35rem; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .7rem; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; }

.version-note { margin: 1.2rem 0 0; color: var(--muted); font-size: .8rem; font-style: italic; }

.chapter-footer { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin: 1rem 0 0; }
.chapter-footer a { min-height: 5rem; padding: 1rem; border: 2px solid var(--ink); background: var(--paper); color: var(--ink); text-decoration: none; transition: background 140ms ease-out; }
.chapter-footer a:hover { background: var(--accent-soft); }
.chapter-footer a:last-child { text-align: right; }
.chapter-footer small { display: block; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .72rem; text-transform: uppercase; letter-spacing: .06em; }

.home-hero { position: relative; margin: 0 0 1.5rem; padding: .6rem; border: 2px solid var(--ink); background: var(--paper); box-shadow: var(--shadow); }
.home-hero::before {
    content: "";
    position: absolute;
    inset: .6rem;
    border: 1px solid var(--line-strong);
    pointer-events: none;
    z-index: 1;
}
.home-hero img { display: block; width: 100%; height: auto; filter: saturate(.92) contrast(1.02); }
.home-hero-tag {
    position: absolute;
    left: 1.4rem;
    bottom: 1.4rem;
    z-index: 2;
    padding: .35rem .7rem;
    border: 1px solid color-mix(in srgb, var(--ink) 25%, transparent);
    background: color-mix(in srgb, var(--paper) 82%, transparent);
    backdrop-filter: blur(6px);
    color: var(--ink);
    font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    font-size: .74rem;
    font-weight: 700;
    letter-spacing: .04em;
}
.home-intro { padding: clamp(2rem, 6vw, 5.5rem); }
.home-intro h1 { max-width: 12ch; }
.path { margin-top: 3rem; counter-reset: chapter; }
.path-card { display: grid; grid-template-columns: 4.5rem 1fr auto; gap: 1rem; align-items: start; padding: 1.3rem 0; color: var(--ink); border-top: 1px solid var(--line-strong); text-decoration: none; transition: padding-left 140ms ease-out; }
.path-card:last-child { border-bottom: 1px solid var(--line-strong); }
.path-card:hover { padding-left: .5rem; background: linear-gradient(90deg, var(--accent-soft), transparent 60%); }
.path-card:hover h2 { color: var(--accent-strong); }
.path-card .index { font-family: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Noto Serif TC", serif; font-size: 2.1rem; color: var(--line-strong); font-variant-numeric: tabular-nums; line-height: 1; }
.path-card h2 { margin: 0 0 .25rem; font-size: 1.18rem; transition: color 160ms ease-out; }
.path-card p { margin: 0; color: var(--muted); }
.path-card time { color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; white-space: nowrap; font-size: .78rem; }
.acknowledgement, .planned { margin-top: 4rem; padding: 1.4rem; border: 1px dashed var(--line-strong); }
.acknowledgement { border-style: solid; background: var(--bg); }
.acknowledgement h2, .planned h2 { margin-top: 0; }

.footer { margin-top: 2rem; padding: 1rem 0; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; text-align: center; }
.drawer-backdrop { display: none; }

@media (max-width: 860px) {
    .js .menu-button { display: inline-grid; }
    .sidebar { position: static; width: auto; margin: 3.75rem 1rem 0; border: 2px solid var(--ink); }
    .js .sidebar { position: fixed; inset: 3.75rem auto 0 0; width: var(--sidebar); margin: 0; transform: translateX(-100%); transition: transform 180ms cubic-bezier(.23, 1, .32, 1); box-shadow: var(--shadow); }
    .js [data-drawer="open"] .sidebar { transform: translateX(0); }
    .js [data-drawer="open"] .drawer-backdrop { display: block; position: fixed; inset: 3.75rem 0 0; z-index: 15; border: 0; background: rgba(0, 0, 0, .28); }
    .shell { padding: 1rem; }
    .js .shell { padding-top: 5.25rem; }
    .article { padding: 1.4rem; }
    .home-hero-tag { left: .8rem; bottom: .8rem; font-size: .68rem; padding: .3rem .55rem; }
    .compare { grid-template-columns: 1fr; }
    .path-card { grid-template-columns: 3rem 1fr; }
    .path-card time { grid-column: 2; }
    .step-flow ol { flex-direction: column; }
    .step-flow .step-arrow { display: block; transform: rotate(90deg); }
    .decision-tree ol, .decision-tree ul { padding-left: .85rem; }
}

@media (max-width: 520px) {
    .brand small { display: none; }
    .chapter-footer { grid-template-columns: 1fr; }
    .chapter-footer a:last-child { text-align: left; }
}

.architecture-preview button { position: relative; display: block; width: 100%; padding: 0; border: 0; background: transparent; color: inherit; cursor: zoom-in; }
.architecture-preview button::after { content: ""; position: absolute; inset: 0; border: 3px solid transparent; pointer-events: none; transition: border-color .15s ease, background .15s ease; }
.architecture-preview button:hover::after, .architecture-preview button:focus-visible::after { border-color: var(--accent); background: color-mix(in srgb, var(--accent) 5%, transparent); }
.architecture-preview button span { position: absolute; right: .75rem; bottom: .75rem; padding: .45rem .7rem; background: color-mix(in srgb, var(--code) 88%, transparent); color: var(--code-ink); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .75rem; font-weight: 700; }
.architecture-dialog { width: 90vw; max-width: none; height: 90vh; max-height: none; margin: auto; padding: 0; border: 1px solid var(--line-strong); background: var(--paper); color: var(--ink); box-shadow: 0 24px 80px rgb(0 0 0 / .35); overflow: hidden; }
.architecture-dialog[open] { display: grid; grid-template-rows: auto 1fr; }
.architecture-dialog::backdrop { background: rgb(5 12 18 / .72); backdrop-filter: blur(5px); }
.architecture-dialog header { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: .7rem 1rem; border-bottom: 1px solid var(--line); }
.architecture-dialog header small { color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; }
.architecture-dialog header h2 { margin: .1rem 0 0; font-size: 1rem; }
.architecture-dialog header button { padding: .45rem .7rem; border: 1px solid var(--line-strong); background: var(--paper); color: var(--ink); cursor: pointer; }
.architecture-dialog object { display: block; width: 100%; height: 100%; border: 0; background: #07131f; }
@media (max-width: 860px) {
    .architecture-dialog { width: 94vw; height: 88vh; }
    .architecture-preview button span { position: static; display: block; margin-top: .6rem; background: var(--accent-soft); color: var(--accent-strong); }
}

/* Diagram embeds */
figure.diagram-embed {
    margin: 2rem 0;
    padding: 1rem;
    border: 1px solid var(--line-strong);
    border-radius: 0;
    background: var(--paper);
    text-align: center;
}
figure.diagram-embed img {
    max-width: 100%;
    height: auto;
    border-radius: 0;
    display: block;
    margin: 0 auto;
    box-shadow: none;
}
figure.diagram-embed figcaption {
    margin-top: 0.85rem;
    color: var(--muted);
    font-size: 0.88rem;
    line-height: 1.5;
    font-style: italic;
}
figure.data-anim { margin: 1.8rem 0; padding: 1.1rem 1.1rem 1.2rem; border: 1px solid var(--line-strong); background: var(--bg); }
figure.data-anim figcaption { margin-top: .65rem; color: var(--muted); font-size: .85rem; font-style: italic; }
.anim-track { display: flex; flex-wrap: wrap; align-items: stretch; gap: .5rem; list-style: none; margin: 0; padding: 0; }
.anim-node { flex: 1 1 9.5rem; min-width: 9rem; padding: .7rem .85rem; border: 1px solid var(--line-strong); border-radius: 0; background: var(--paper); }
.anim-title { display: block; font-weight: 700; font-size: .92rem; }
.anim-data { display: block; margin-top: .35rem; color: var(--muted); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .76rem; line-height: 1.5; overflow-wrap: anywhere; }
.anim-arrow { align-self: center; padding: 0 .1rem; color: var(--muted); }
.data-anim .chip { display: inline-block; margin: .2rem .25rem 0 0; padding: .02rem .4rem; border: 1px solid var(--line-strong); border-radius: 0; background: var(--soft); color: var(--ink); font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .72rem; }
.data-anim .chip.keep { border-color: var(--accent); }
.data-anim .chip.drop { text-decoration: line-through; animation: anim-chip-drop 9s infinite; }
.anim-toggle { margin-top: .6rem; padding: .28rem .6rem; border: 1px solid var(--line-strong); border-radius: 0; background: var(--paper); color: var(--muted); cursor: pointer; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .75rem; }

@keyframes anim-node-active {
    0% { border-color: var(--line-strong); background: var(--paper); box-shadow: none; }
    4%, 16% { border-color: var(--rust); background: var(--accent-soft); box-shadow: 0 0 0 3px color-mix(in srgb, var(--rust) 20%, transparent); }
    24%, 100% { border-color: var(--line-strong); background: var(--paper); box-shadow: none; }
}
@keyframes anim-arrow-active {
    0% { color: var(--muted); }
    4%, 16% { color: var(--rust-strong); }
    24%, 100% { color: var(--muted); }
}
@keyframes anim-chip-drop {
    0%, 20% { opacity: 1; }
    26%, 90% { opacity: .3; }
    97%, 100% { opacity: 1; }
}
.anim-node.s1 { animation: anim-node-active 9s infinite; }
.anim-node.s2 { animation: anim-node-active 9s infinite 1.5s; }
.anim-node.s3 { animation: anim-node-active 9s infinite 3s; }
.anim-node.s4 { animation: anim-node-active 9s infinite 4.5s; }
.anim-node.s5 { animation: anim-node-active 9s infinite 6s; }
.anim-node.s6 { animation: anim-node-active 9s infinite 7.5s; }
.anim-arrow.a1 { animation: anim-arrow-active 9s infinite .75s; }
.anim-arrow.a2 { animation: anim-arrow-active 9s infinite 2.25s; }
.anim-arrow.a3 { animation: anim-arrow-active 9s infinite 3.75s; }
.anim-arrow.a4 { animation: anim-arrow-active 9s infinite 5.25s; }
.anim-arrow.a5 { animation: anim-arrow-active 9s infinite 6.75s; }
.data-anim.paused .anim-node, .data-anim.paused .anim-arrow, .data-anim.paused .chip { animation-play-state: paused; }

@media (max-width: 860px) {
    .anim-track { flex-direction: column; }
    .anim-arrow { transform: rotate(90deg); }
}

@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
    .anim-node, .anim-arrow, .data-anim .chip { animation: none !important; }
    .anim-toggle { display: none; }
}

@media (prefers-reduced-transparency: reduce) {
    .topbar { background: var(--paper); backdrop-filter: none; }
}

@media print {
    :root { color-scheme: light; --paper: white; --ink: black; --muted: #444; --line: #bbb; --bg: white; }
    body { background-image: none; }
    .topbar, .sidebar, .chapter-footer, .footer, .copy-button, .chapter-toc, .home-hero { display: none !important; }
    .shell { padding: 0; }
    .reader { width: auto; }
    .article { padding: 0; border: 0; box-shadow: none; }
    .article::before { display: none; }
    a { color: inherit; text-decoration: none; }
    a[href^="http"]::after { content: " (" attr(href) ")"; font-size: .8em; }
    pre { white-space: pre-wrap; break-inside: avoid; }
    h2, h3 { break-after: avoid; }
    .step-flow li, .decision-tree li { break-inside: avoid; }
    .anim-toggle { display: none !important; }
    .anim-node, .anim-arrow, .data-anim .chip { animation: none !important; }
    figure.data-anim { break-inside: avoid; }
}