/* ---------- tokens ---------- */
:root {
  --bg: #f6f5f1;
  --surface: #ffffff;
  --surface-2: #efede7;
  --ink: #1b1c1e;
  --ink-2: #3a3d42;
  --muted: #62666d;
  --line: #e0ded7;
  --line-2: #cfccc3;
  --accent: #1f7a5a;
  --accent-hover: #186649;
  --accent-ink: #ffffff;
  --accent-soft: #e2f0e9;
  --accent-line: #b7dac9;
  --tok-bg: #fff1c7;
  --tok-ink: #6b4a00;
  --warn-bg: #fff5e0;
  --warn-line: #f0d398;
  --warn-ink: #7a4d00;
  --bad-bg: #fdeeec;
  --bad-line: #f2c2bb;
  --bad-ink: #9e2a1c;
  --term-bg: #16181d;
  --term-bar: #22252c;
  --term-ink: #e7e8ea;
  --term-muted: #8a909b;
  --term-prompt: #5fd3a2;
  --out-bg: #f1efe9;
  --mark: #d9eee3;
  --shadow: 0 1px 2px rgba(20, 20, 20, 0.04), 0 4px 14px rgba(20, 20, 20, 0.05);
  --radius: 12px;
  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #111214;
    --surface: #191b1e;
    --surface-2: #202327;
    --ink: #ececed;
    --ink-2: #c9cbcf;
    --muted: #9ba0a8;
    --line: #2a2d32;
    --line-2: #3a3e45;
    --accent: #4cc491;
    --accent-hover: #6ad3a6;
    --accent-ink: #0c1f17;
    --accent-soft: #15302a;
    --accent-line: #245443;
    --tok-bg: #3b3013;
    --tok-ink: #f5d27a;
    --warn-bg: #2d2412;
    --warn-line: #54421c;
    --warn-ink: #f1c778;
    --bad-bg: #331a17;
    --bad-line: #5a2a24;
    --bad-ink: #f3a39a;
    --term-bg: #0b0c0e;
    --term-bar: #16181c;
    --out-bg: #1e2125;
    --mark: #1b3a2e;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 16px rgba(0, 0, 0, 0.25);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #111214; --surface: #191b1e; --surface-2: #202327; --ink: #ececed; --ink-2: #c9cbcf; --muted: #9ba0a8;
  --line: #2a2d32; --line-2: #3a3e45; --accent: #4cc491; --accent-hover: #6ad3a6; --accent-ink: #0c1f17;
  --accent-soft: #15302a; --accent-line: #245443; --tok-bg: #3b3013; --tok-ink: #f5d27a; --warn-bg: #2d2412;
  --warn-line: #54421c; --warn-ink: #f1c778; --bad-bg: #331a17; --bad-line: #5a2a24; --bad-ink: #f3a39a;
  --term-bg: #0b0c0e; --term-bar: #16181c; --out-bg: #1e2125; --mark: #1b3a2e;
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.3), 0 4px 16px rgba(0, 0, 0, 0.25); color-scheme: dark;
}

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.6 var(--sans);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-underline-offset: 2px; }
a:hover { color: var(--accent-hover); }
p { margin: 0 0 0.6em; }
p:last-child { margin-bottom: 0; }
code, kbd { font-family: var(--mono); font-size: 0.86em; }
:not(pre) > code {
  background: var(--surface-2);
  border: 1px solid var(--line);
  padding: 0.08em 0.36em;
  border-radius: 5px;
  white-space: nowrap;
}
kbd {
  display: inline-block;
  padding: 0.05em 0.45em;
  border: 1px solid var(--line-2);
  border-bottom-width: 2px;
  border-radius: 5px;
  background: var(--surface);
  font-size: 0.8em;
}
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
h1:focus { outline: none; }
.small { font-size: 0.9rem; color: var(--muted); }

/* ---------- chrome ---------- */
.top {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 14px;
  height: 56px;
  padding: 0 24px;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line);
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--ink); text-decoration: none; font-weight: 600; letter-spacing: -0.01em; }
.brand:hover { color: var(--ink); }
.logo { color: var(--accent); display: flex; }
.section { color: var(--muted); font-size: 0.9rem; padding-left: 14px; border-left: 1px solid var(--line-2); }
.user-chip {
  margin-left: auto;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 4px 12px 4px 4px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--ink-2);
  font: 500 0.88rem var(--sans);
  cursor: pointer;
}
.user-chip:hover { border-color: var(--line-2); }
.user-chip img { border-radius: 50%; display: block; }
.user-chip[hidden] { display: none; }

.stage { flex: 1; padding: 40px 24px 56px; }

.nav {
  position: sticky;
  bottom: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 12px 24px calc(12px + env(safe-area-inset-bottom));
  background: color-mix(in srgb, var(--bg) 90%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-top: 1px solid var(--line);
}
.progress { flex: 1; min-width: 0; }
.bar { display: flex; gap: 3px; }
.seg {
  flex: 1;
  height: 8px;
  padding: 0;
  border: 0;
  border-radius: 3px;
  background: var(--line);
  cursor: pointer;
  transition: background 0.15s, transform 0.15s;
}
.seg.done { background: var(--accent); opacity: 0.55; }
.seg.open { background: var(--line-2); }
.seg.cur { background: var(--accent); }
.seg.locked { cursor: not-allowed; opacity: 0.6; }
.seg:not(:disabled):hover { transform: scaleY(1.5); }
.progress-meta { display: flex; justify-content: space-between; gap: 12px; margin-top: 6px; font-size: 0.8rem; color: var(--muted); font-variant-numeric: tabular-nums; }
.next-hint { text-align: right; }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 42px;
  padding: 0 18px;
  border: 1px solid var(--accent);
  border-radius: 10px;
  background: var(--accent);
  color: var(--accent-ink);
  font: 600 0.95rem var(--sans);
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
  transition: background 0.15s, border-color 0.15s, opacity 0.15s;
}
.btn:hover { background: var(--accent-hover); border-color: var(--accent-hover); color: var(--accent-ink); }
.btn:disabled { opacity: 0.4; cursor: not-allowed; }
.btn:disabled:hover { background: var(--accent); border-color: var(--accent); }
.btn-ghost { background: var(--surface); color: var(--ink); border-color: var(--line-2); }
.btn-ghost:hover { background: var(--surface-2); color: var(--ink); border-color: var(--line-2); }
.btn-ghost:disabled:hover { background: var(--surface); border-color: var(--line-2); }
.linkbtn { border: 0; background: none; padding: 0; color: var(--muted); font: inherit; font-size: 0.85rem; text-decoration: underline; text-underline-offset: 2px; cursor: pointer; }
.linkbtn:hover { color: var(--ink); }

/* ---------- slide ---------- */
.slide { max-width: 1140px; margin: 0 auto; animation: in 0.28s ease-out; }
@keyframes in { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }
@media (prefers-reduced-motion: reduce) { .slide { animation: none; } .seg { transition: none; } }
.kicker { font-size: 0.8rem; font-weight: 600; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); margin-bottom: 10px; }
.slide h1 { margin: 0 0 12px; font-size: clamp(1.9rem, 3.6vw, 2.7rem); line-height: 1.12; letter-spacing: -0.025em; font-weight: 700; text-wrap: balance; }
.lead { font-size: clamp(1.05rem, 1.6vw, 1.2rem); color: var(--ink-2); max-width: 760px; margin-bottom: 28px; text-wrap: pretty; }
.cols { display: grid; grid-template-columns: minmax(0, 1fr) 340px; gap: 40px; align-items: start; }
.slide-wide .cols { grid-template-columns: minmax(0, 1fr); }
.slide-wide .col-main { max-width: 980px; }
.col-aside { display: flex; flex-direction: column; gap: 16px; position: sticky; top: 80px; }
.slide .col-main > * + * { margin-top: 24px; }

.tok { background: var(--tok-bg); color: var(--tok-ink); padding: 0 0.25em; border-radius: 4px; font-weight: 600; }
.term .tok, .out .tok { background: rgba(255, 209, 102, 0.16); color: #ffd98a; font-weight: 500; }
.out .tok { background: var(--tok-bg); color: var(--tok-ink); }

/* steps */
.steps { list-style: none; margin: 0; padding: 0; counter-reset: s; }
.steps > li { position: relative; padding: 0 0 26px 46px; counter-increment: s; }
.steps > li::before {
  content: counter(s);
  position: absolute;
  left: 0;
  top: 0;
  width: 30px;
  height: 30px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid var(--accent-line);
  font-weight: 700;
  font-size: 0.88rem;
}
.steps > li::after { content: ""; position: absolute; left: 15px; top: 36px; bottom: 6px; width: 1px; background: var(--line); }
.steps > li:last-child { padding-bottom: 0; }
.steps > li:last-child::after { display: none; }
.step-h { font-weight: 600; font-size: 1.05rem; line-height: 30px; margin-bottom: 8px; }
.steps > li > * + * { margin-top: 10px; }
ul.plain { margin: 0; padding-left: 1.1em; }
ul.plain li + li { margin-top: 4px; }

/* terminal */
.term { border-radius: 10px; overflow: hidden; background: var(--term-bg); box-shadow: var(--shadow); }
.term-bar { display: flex; align-items: center; gap: 10px; padding: 7px 8px 7px 12px; background: var(--term-bar); }
.term-dots { display: flex; gap: 6px; }
.term-dots i { width: 10px; height: 10px; border-radius: 50%; background: #3b3f47; }
.term-title { color: var(--term-muted); font-size: 0.75rem; font-weight: 500; flex: 1; }
.copy {
  border: 1px solid #3a3e46;
  background: transparent;
  color: #c9ccd2;
  font: 500 0.75rem var(--sans);
  padding: 3px 10px;
  border-radius: 6px;
  cursor: pointer;
}
.copy:hover { background: #2c3038; color: #fff; }
.copy.did { color: var(--term-prompt); border-color: #2f5e4a; }
.term pre { margin: 0; padding: 14px 16px 16px; overflow-x: auto; color: var(--term-ink); font: 0.88rem/1.7 var(--mono); }
.term code { font-size: inherit; }
.t-line { display: block; white-space: pre; }
.t-cmd::before { content: "$ "; color: var(--term-prompt); user-select: none; -webkit-user-select: none; }
.t-comment { color: var(--term-muted); }

/* expected output */
.out { border: 1px dashed var(--line-2); border-radius: 10px; background: var(--out-bg); overflow: hidden; }
.out-label { padding: 8px 14px 0; font-size: 0.72rem; font-weight: 600; letter-spacing: 0.05em; text-transform: uppercase; color: var(--muted); }
.out pre { margin: 0; padding: 6px 14px 12px; overflow-x: auto; font: 0.82rem/1.65 var(--mono); color: var(--ink-2); }
.out mark { background: var(--mark); color: var(--ink); border-radius: 3px; padding: 0 2px; }

/* notes */
.note { border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); padding: 16px 18px; font-size: 0.94rem; color: var(--ink-2); }
.note-label { font-size: 0.75rem; font-weight: 700; letter-spacing: 0.05em; text-transform: uppercase; color: var(--muted); margin-bottom: 8px; }
.note-why { border-color: var(--accent-line); background: var(--accent-soft); }
.note-why .note-label { color: var(--accent); }
.note-warn { border-color: var(--warn-line); background: var(--warn-bg); }
.note-warn .note-label { color: var(--warn-ink); }
.note .term { margin-top: 10px; }
.note .term pre { white-space: pre-wrap; }
.note .term .t-line { white-space: pre-wrap; word-break: break-word; }
ol.loop { margin: 0; padding-left: 1.3em; }
ol.loop li + li { margin-top: 3px; }

/* where strip */
.where { display: flex; flex-wrap: wrap; align-items: center; gap: 6px; margin: -10px 0 28px; font-size: 0.85rem; }
.where-l { color: var(--muted); margin-right: 4px; }
.where-p { padding: 4px 10px; border-radius: 999px; border: 1px solid var(--line); background: var(--surface); color: var(--muted); }
.where-p.past { color: var(--ink-2); }
.where-p.on { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
.where-a { color: var(--line-2); }

/* flow diagram */
.flow { display: flex; align-items: stretch; gap: 0; }
.flow-node {
  flex: 1;
  min-width: 0;
  position: relative;
  padding: 18px 16px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}
.flow-remote { border-color: var(--accent-line); background: var(--accent-soft); }
.flow-tag { display: inline-block; font-size: 0.68rem; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--muted); margin-bottom: 6px; }
.flow-remote .flow-tag { color: var(--accent); }
.flow-t { font-weight: 700; font-size: 1.02rem; line-height: 1.3; margin-bottom: 6px; overflow-wrap: anywhere; }
.flow-s { font-size: 0.88rem; color: var(--muted); line-height: 1.5; }
.flow-edge { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 4px; padding: 0 6px; min-width: 96px; }
.flow-edge code { font-size: 0.78rem; background: var(--surface); }
.flow-arrow { display: block; width: 100%; height: 2px; background: var(--accent); position: relative; }
.flow-arrow::after { content: ""; position: absolute; right: -1px; top: -5px; border: 6px solid transparent; border-left: 8px solid var(--accent); border-right: 0; }
.flow-back { color: var(--muted); font-size: 0.95rem; }

/* definitions */
.defs { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; margin-bottom: 0; }
.defs > div { border-top: 2px solid var(--line); padding-top: 10px; }
.defs dt { font-weight: 700; margin-bottom: 4px; }
.defs dd { margin: 0; color: var(--ink-2); font-size: 0.93rem; }

/* cards */
.cards3 { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; }
.card { border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); padding: 16px; }
.card-t { font-weight: 700; margin-bottom: 6px; }
.card p { font-size: 0.92rem; color: var(--ink-2); }

/* branch graph */
.graph { margin-left: 0; margin-right: 0; margin-bottom: 0; padding: 12px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.graph svg { width: 100%; height: auto; display: block; }
.g-main { stroke: var(--ink-2); stroke-width: 4; stroke-linecap: round; }
.g-branch { stroke: var(--accent); stroke-width: 4; fill: none; stroke-linecap: round; }
.g-dot { fill: var(--surface); stroke: var(--ink-2); stroke-width: 4; }
.g-dot-b { stroke: var(--accent); }
.g-merge { fill: var(--accent); stroke: var(--accent); }
.g-lbl { font: 600 17px var(--mono); fill: var(--ink-2); }
.g-lbl-b { fill: var(--accent); }
.g-note { font: 600 15px var(--sans); fill: var(--muted); }

/* Q&A table */
.qa { width: 100%; border-collapse: collapse; font-size: 0.92rem; margin-top: 8px; }
.qa td { padding: 8px 10px; border-top: 1px solid var(--line); vertical-align: top; }
.qa tr:last-child td { border-bottom: 1px solid var(--line); }
.qa td:first-child { color: var(--muted); }
.qa td:last-child { white-space: nowrap; }

/* PR bar */
.pr-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); font-size: 0.88rem; }
.pr-bar > span:not(.pr-arrow) { padding: 3px 9px; border: 1px solid var(--line-2); border-radius: 6px; background: var(--surface-2); }
.pr-arrow { color: var(--muted); }

/* username form */
.user-form { padding: 20px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow); }
.user-form label { display: block; font-weight: 600; margin-bottom: 8px; }
.user-row { display: flex; align-items: stretch; border: 1px solid var(--line-2); border-radius: 10px; overflow: hidden; background: var(--bg); }
.user-row:focus-within { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.at { display: flex; align-items: center; padding: 0 4px 0 14px; color: var(--muted); font: 0.95rem var(--mono); }
.user-row input { flex: 1; min-width: 0; border: 0; outline: 0; background: transparent; color: var(--ink); padding: 12px 14px 12px 0; font: 500 1rem var(--mono); }
.user-form .hint { margin-top: 8px; font-size: 0.85rem; color: var(--muted); }
.user-form + .gate { margin-top: 12px; }

/* gate */
.slide .gate { margin-top: 32px; padding-top: 24px; border-top: 1px solid var(--line); }
.gate-check { display: flex; flex-wrap: wrap; align-items: flex-start; gap: 14px; }
.gate-t { font-weight: 600; margin-bottom: 10px; }
.tick { display: flex; align-items: flex-start; gap: 10px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface); cursor: pointer; }
.tick + .tick { margin-top: 8px; }
.tick:hover { border-color: var(--line-2); }
.tick input { margin: 4px 0 0; width: 18px; height: 18px; accent-color: var(--accent); flex: none; }
.tick:has(input:checked) { border-color: var(--accent-line); background: var(--accent-soft); }
.result:empty { display: none; }
.result { flex: 1 1 320px; display: flex; gap: 10px; align-items: flex-start; padding: 10px 14px; border-radius: 10px; border: 1px solid var(--line); background: var(--surface); font-size: 0.93rem; }
.result.ok { border-color: var(--accent-line); background: var(--accent-soft); }
.result.bad { border-color: var(--bad-line); background: var(--bad-bg); color: var(--ink); }
.r-icon { flex: none; width: 22px; height: 22px; border-radius: 50%; display: grid; place-items: center; font-weight: 700; font-size: 0.8rem; background: var(--accent); color: var(--accent-ink); margin-top: 1px; }
.result.bad .r-icon { background: var(--bad-ink); color: var(--bad-bg); }
.result .skip { margin-top: 8px; }
.spinner { flex: none; width: 18px; height: 18px; margin-top: 2px; border: 2px solid var(--line-2); border-top-color: var(--accent); border-radius: 50%; animation: spin 0.7s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.found { display: inline-flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.found img { border-radius: 50%; }

/* solo */
.solo { list-style: none; padding: 0; margin: 0; counter-reset: s; }
.solo > li { counter-increment: s; position: relative; padding: 14px 16px 14px 56px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.solo > li + li { margin-top: 10px; }
.solo > li::before { content: counter(s); position: absolute; left: 16px; top: 13px; width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; background: var(--accent-soft); color: var(--accent); border: 1px solid var(--accent-line); font-weight: 700; font-size: 0.85rem; }
.solo > li > span { display: block; line-height: 30px; }
.solo details { margin-top: 6px; }
.solo summary { cursor: pointer; color: var(--accent); font-size: 0.88rem; font-weight: 600; width: max-content; }
.solo details[open] summary { margin-bottom: 10px; }

/* cheat sheet */
.cheat { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.cheat > div { border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); padding: 16px; }
.cheat h3 { margin: 0 0 10px; font-size: 0.78rem; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent); }
.cheat dl { margin: 0; }
.cheat dt { margin-top: 10px; }
.cheat dt:first-child { margin-top: 0; }
.cheat dt code { white-space: normal; word-break: break-word; }
.cheat dd { margin: 2px 0 0; font-size: 0.88rem; color: var(--muted); }
.done-actions { display: flex; }

/* ---------- responsive ---------- */
@media (max-width: 1020px) {
  .cols { grid-template-columns: minmax(0, 1fr); gap: 28px; }
  .col-aside { position: static; }
}
@media (max-width: 820px) {
  .flow { flex-direction: column; }
  .flow-edge { flex-direction: row; min-width: 0; padding: 6px 0; height: 52px; gap: 10px; }
  .flow-arrow { width: 2px; height: 100%; order: -1; }
  .flow-arrow::after { right: -5px; top: auto; bottom: -1px; border: 6px solid transparent; border-top: 8px solid var(--accent); border-bottom: 0; }
  .cards3 { grid-template-columns: minmax(0, 1fr); }
}
@media (max-width: 640px) {
  .top { padding: 0 16px; gap: 10px; }
  .brand-t, .section { display: none; }
  .brand + .section { display: inline; border-left: 0; padding-left: 0; }
  .stage { padding: 28px 16px 40px; }
  .nav { padding: 10px 16px calc(10px + env(safe-area-inset-bottom)); gap: 12px; }
  .nav .btn { padding: 0 14px; }
  .next-hint { display: none; }
  .steps > li { padding-left: 40px; }
  .term pre { font-size: 0.8rem; }
  .qa td:last-child { white-space: normal; }
  .solo > li { padding-left: 52px; }
}

/* welcome: gate lives inside the username card */
.slide .user-form .gate { margin-top: 16px; padding-top: 0; border-top: 0; }
.user-form .gate-check .btn { width: 100%; }
.user-form .result { flex-basis: 100%; }