/* ── themes ─────────────────────────────────────────────── */
:root {
  --scale: 1;
  --serif: "Iowan Old Style", "Palatino", "Book Antiqua", Georgia, "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter", Roboto, sans-serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  --body-font: var(--serif);
  --measure: 68rem;
}
:root[data-font="sans"] { --body-font: var(--sans); }

:root, :root[data-theme="light"] {
  --bg: #faf9f5;
  --surface: #f1efe9;
  --surface-2: #e9e6de;
  --ink: #2b2a26;
  --ink-soft: #56544d;
  --muted: #8b887e;
  --accent: #9c4a26;
  --accent-soft: #9c4a2622;
  --border: #e2dfd6;
  --shadow: 0 8px 32px rgba(60, 50, 30, .12);
  --code-bg: #f0eee7;
  --hl-key: #8a3fa0; --hl-str: #3d7a44; --hl-num: #a05a1f;
  --hl-cmt: #97948a; --hl-fn: #2f6da6; --hl-attr: #8a6116;
}
:root[data-theme="sepia"] {
  --bg: #f6ecd9;
  --surface: #efe2c8;
  --surface-2: #e7d8ba;
  --ink: #453722;
  --ink-soft: #6b5a3e;
  --muted: #998664;
  --accent: #8c4a2f;
  --accent-soft: #8c4a2f22;
  --border: #e2d3b4;
  --shadow: 0 8px 32px rgba(90, 65, 25, .14);
  --code-bg: #eee0c4;
  --hl-key: #8a3fa0; --hl-str: #4a7a3a; --hl-num: #a05a1f;
  --hl-cmt: #a08d6b; --hl-fn: #2f6da6; --hl-attr: #8a6116;
}
:root[data-theme="dark"] {
  --bg: #16181c;
  --surface: #1e2126;
  --surface-2: #262a30;
  --ink: #d8d4ca;
  --ink-soft: #a9a497;
  --muted: #7c7870;
  --accent: #d4a373;
  --accent-soft: #d4a37326;
  --border: #2c3037;
  --shadow: 0 8px 32px rgba(0, 0, 0, .45);
  --code-bg: #1d2025;
  --hl-key: #c792ea; --hl-str: #9ece6a; --hl-num: #e0af68;
  --hl-cmt: #6a7079; --hl-fn: #7aa2f7; --hl-attr: #d7ba7d;
}

/* ── base ───────────────────────────────────────────────── */
* { box-sizing: border-box; margin: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--body-font);
  font-size: calc(1.15rem * var(--scale));
  line-height: 1.72;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background .35s ease, color .35s ease;
}
::selection { background: var(--accent-soft); }

main {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 5.5rem 1.5rem 6rem;
}

/* ── reading progress ───────────────────────────────────── */
#progress {
  position: fixed; top: 0; left: 0; z-index: 40;
  height: 3px; width: 0;
  background: var(--accent);
  border-radius: 0 2px 2px 0;
  transition: width .08s linear;
}

/* ── toolbar ────────────────────────────────────────────── */
#toolbar {
  position: fixed; top: .9rem; z-index: 30;
  left: 1rem; right: 1rem;
  display: flex; justify-content: space-between; align-items: center;
  pointer-events: none;
  opacity: 1;
  transition: opacity .3s ease, transform .3s ease;
}
#toolbar.hidden { opacity: 0; transform: translateY(-6px); pointer-events: none; }
#toolbar > * { pointer-events: auto; }
.toolbar-group {
  display: flex; align-items: center; gap: .1rem;
  background: color-mix(in srgb, var(--surface) 82%, transparent);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  border-radius: 99px;
  padding: .25rem .45rem;
  box-shadow: var(--shadow);
}
#toolbar button {
  appearance: none; border: 0; background: transparent;
  color: var(--ink-soft);
  font: inherit; font-size: .85rem;
  width: 2.1rem; height: 2.1rem;
  display: grid; place-items: center;
  border-radius: 99px;
  cursor: pointer;
  transition: background .15s ease, color .15s ease;
}
#toolbar button:hover { background: var(--surface-2); color: var(--ink); }
#toolbar button.on { color: var(--accent); background: var(--accent-soft); }
#toolbar button svg { width: 1.05rem; height: 1.05rem; }
#btn-toc {
  background: color-mix(in srgb, var(--surface) 82%, transparent);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border) !important;
  box-shadow: var(--shadow);
}
#toolbar #btn-bionic { width: auto; padding: 0 .6rem; font-size: .78rem; letter-spacing: .01em; }
.a-small { font-size: .72rem; font-family: var(--sans); }
.a-large { font-size: .95rem; font-family: var(--sans); }
.ff { font-size: .82rem; }
.sep { width: 1px; height: 1.1rem; background: var(--border); margin: 0 .3rem; }

/* ── table of contents ──────────────────────────────────── */
#toc {
  position: fixed; top: 0; left: 0; bottom: 0; z-index: 50;
  width: min(20rem, 85vw);
  background: var(--surface);
  border-right: 1px solid var(--border);
  transform: translateX(-102%);
  transition: transform .32s cubic-bezier(.25,.9,.3,1);
  display: flex; flex-direction: column;
  box-shadow: none;
}
#toc.open { transform: none; box-shadow: var(--shadow); }
.toc-head {
  padding: 1.4rem 1.5rem .9rem;
  font-family: var(--sans); font-size: .72rem; font-weight: 600;
  letter-spacing: .14em; text-transform: uppercase; color: var(--muted);
}
.toc-links { overflow-y: auto; flex: 1; padding: 0 .75rem 1rem; }
.toc-link {
  display: block;
  padding: .38rem .75rem;
  border-radius: .5rem;
  color: var(--ink-soft);
  font-family: var(--sans); font-size: .86rem; line-height: 1.4;
  text-decoration: none;
  transition: background .15s ease, color .15s ease;
}
.toc-link:hover { background: var(--surface-2); color: var(--ink); }
.toc-link.active { color: var(--accent); background: var(--accent-soft); }
.toc-l1 { font-weight: 600; }
.toc-l2 { padding-left: 1.5rem; }
.toc-l3 { padding-left: 2.25rem; font-size: .8rem; }
.toc-l4 { padding-left: 3rem; font-size: .8rem; }
.toc-foot {
  padding: .9rem 1.5rem 1.1rem;
  border-top: 1px solid var(--border);
  display: flex; flex-wrap: wrap; gap: .35rem .8rem;
  font-family: var(--sans); font-size: .7rem; color: var(--muted);
}
kbd {
  font-family: var(--mono); font-size: .92em;
  background: var(--surface-2); border: 1px solid var(--border);
  border-radius: .25rem; padding: 0 .3em;
}
#toc-backdrop {
  position: fixed; inset: 0; z-index: 45;
  background: rgba(0,0,0,.25);
  opacity: 0; pointer-events: none;
  transition: opacity .3s ease;
}
#toc-backdrop.show { opacity: 1; pointer-events: auto; }

/* ── document meta ──────────────────────────────────────── */
.doc-meta {
  display: flex; justify-content: space-between; align-items: baseline;
  gap: 1rem; flex-wrap: wrap;
  margin-bottom: 3rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
  font-family: var(--sans); font-size: .78rem;
  color: var(--muted);
}
.doc-file { letter-spacing: .06em; }
.doc-end { text-align: center; margin-top: 4.5rem; color: var(--muted); font-size: 1.1rem; }

/* ── article typography ─────────────────────────────────── */
article > * { transition: opacity .3s ease; }

article h1, article h2, article h3, article h4 {
  font-family: var(--body-font);
  font-weight: 650;
  line-height: 1.25;
  letter-spacing: -.01em;
  color: var(--ink);
  scroll-margin-top: 5rem;
  text-wrap: balance;
}
article h1 { font-size: 2.3em; margin: 0 0 1.2rem; letter-spacing: -.02em; }
article h1:not(:first-child) { margin-top: 3.5rem; }
article h2 {
  font-size: 1.55em;
  margin: 3rem 0 1rem;
  padding-top: 2.2rem;
}
article h2::before {
  content: "";
  display: block;
  width: 2.4rem; height: 2px;
  background: var(--accent);
  opacity: .55;
  border-radius: 2px;
  margin-bottom: 2rem;
}
article h3 { font-size: 1.22em; margin: 2.2rem 0 .8rem; }
article h4 { font-size: 1em; margin: 1.8rem 0 .6rem; text-transform: uppercase; letter-spacing: .07em; font-size: .85em; color: var(--ink-soft); }

article p { margin: 0 0 1.35rem; }
article a { color: var(--accent); text-decoration: underline; text-decoration-thickness: 1px; text-underline-offset: 3px; text-decoration-color: color-mix(in srgb, var(--accent) 45%, transparent); transition: text-decoration-color .15s; }
article a:hover { text-decoration-color: var(--accent); }
article strong { font-weight: 680; color: var(--ink); }
article em { font-style: italic; }

article ul, article ol { margin: 0 0 1.35rem; padding-left: 1.4rem; }
article li { margin-bottom: .5rem; padding-left: .3rem; }
article li::marker { color: var(--accent); font-weight: 600; }
article li > ul, article li > ol { margin: .5rem 0 0; }
article input[type="checkbox"] { accent-color: var(--accent); margin-right: .4rem; transform: translateY(1px); }

article blockquote {
  margin: 2rem 0;
  padding: .2rem 0 .2rem 1.4rem;
  border-left: 3px solid var(--accent);
  color: var(--ink-soft);
  font-style: italic;
  font-size: 1.04em;
}
article blockquote p:last-child { margin-bottom: 0; }

article hr {
  border: 0;
  margin: 3.2rem auto;
  text-align: center;
}
article hr::after {
  content: "· · ·";
  color: var(--muted);
  font-size: 1.2rem;
  letter-spacing: .8em;
  padding-left: .8em;
}

article img, article video {
  max-width: 100%;
  border-radius: .6rem;
  margin: 1.8rem 0;
  box-shadow: var(--shadow);
}

article code {
  font-family: var(--mono);
  font-size: .84em;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: .35rem;
  padding: .12em .38em;
  color: var(--ink);
}
article pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: .7rem;
  padding: 1.1rem 1.3rem;
  margin: 1.8rem 0;
  overflow-x: auto;
  line-height: 1.55;
}
article pre code { background: none; border: 0; padding: 0; font-size: .82em; }

article .table-wrap {
  margin: 1.8rem 0;
  overflow-x: auto;
}
article table {
  width: 100%;
  border-collapse: collapse;
  font-size: .92em;
  font-family: var(--sans);
  line-height: 1.5;
}
article th {
  text-align: left;
  font-weight: 600;
  padding: .55rem .8rem;
  border-bottom: 2px solid var(--border);
  color: var(--ink-soft);
  font-size: .82em;
  text-transform: uppercase;
  letter-spacing: .05em;
}
article td { padding: .55rem .8rem; border-bottom: 1px solid var(--border); vertical-align: top; }
article tr:last-child td { border-bottom: 0; }

/* ── branding ───────────────────────────────────────────── */
.doc-brand { margin: 2.8rem 0 0; }
.doc-brand img { display: block; max-height: 3.2rem; max-width: 15rem; }
#drop-hint {
  position: fixed; inset: 1rem; z-index: 60;
  display: grid; place-items: center;
  background: color-mix(in srgb, var(--bg) 75%, transparent);
  backdrop-filter: blur(6px); -webkit-backdrop-filter: blur(6px);
  border: 2px dashed var(--accent);
  border-radius: 1rem;
  font-family: var(--sans); font-size: 1.05rem; color: var(--ink-soft);
  opacity: 0; pointer-events: none;
  transition: opacity .15s ease;
}
#drop-hint.show { opacity: 1; }

/* ── edit mode ──────────────────────────────────────────── */
article.editing {
  outline: 1px dashed color-mix(in srgb, var(--accent) 45%, transparent);
  outline-offset: 1.4rem;
  border-radius: 2px;
  caret-color: var(--accent);
}

/* ── share button + toast ───────────────────────────────── */
#btn-share.busy { pointer-events: none; }
#btn-share.busy svg { animation: share-pulse 1s ease-in-out infinite; }
@keyframes share-pulse { 50% { opacity: .25; } }
#toast {
  position: fixed; bottom: 1.4rem; left: 50%; z-index: 70;
  transform: translateX(-50%) translateY(10px);
  max-width: min(90vw, 44rem);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border); border-radius: 99px;
  padding: .65rem 1.2rem;
  font-family: var(--sans); font-size: .85rem; color: var(--ink);
  box-shadow: var(--shadow);
  cursor: pointer;
  opacity: 0; pointer-events: none;
  transition: opacity .25s ease, transform .25s ease;
}
#toast.show { opacity: 1; pointer-events: auto; transform: translateX(-50%) translateY(0); }

/* ── syntax highlighting ────────────────────────────────── */
.hljs-keyword, .hljs-selector-tag, .hljs-literal, .hljs-built_in, .hljs-type { color: var(--hl-key); }
.hljs-string, .hljs-regexp, .hljs-addition { color: var(--hl-str); }
.hljs-number, .hljs-symbol, .hljs-bullet, .hljs-meta { color: var(--hl-num); }
.hljs-comment, .hljs-quote, .hljs-deletion { color: var(--hl-cmt); font-style: italic; }
.hljs-title, .hljs-function, .hljs-section, .hljs-name { color: var(--hl-fn); }
.hljs-attr, .hljs-attribute, .hljs-variable, .hljs-template-variable, .hljs-params { color: var(--hl-attr); }
.hljs-emphasis { font-style: italic; }
.hljs-strong { font-weight: 700; }

/* ── bionic reading ─────────────────────────────────────── */
b.bio { font-weight: 660; color: var(--ink); }

/* ── focus mode ─────────────────────────────────────────── */
:root[data-focus] article > * { opacity: .28; }
:root[data-focus] article > .in-focus { opacity: 1; }
:root[data-focus] .doc-meta, :root[data-focus] .doc-end, :root[data-focus] .doc-brand { opacity: .28; }

/* ── responsive ─────────────────────────────────────────── */
@media (max-width: 640px) {
  body { font-size: calc(1.05rem * var(--scale)); }
  main { padding-top: 4.5rem; }
  #btn-bionic span { font-size: .72rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; }
}