/* ============================================================
   How a Blockchain Works — styles
   Light-first tokens on :root; dark overrides guarded so a
   manual [data-theme] toggle wins in both directions.
   ============================================================ */

:root {
  --bg: #f7f7f5;
  --bg-raised: #ffffff;
  --bg-sunken: #eeeeea;
  --ink: #1b1b1a;
  --ink-soft: #55554f;
  --ink-faint: #8a8a80;
  --line: #deded7;
  --line-strong: #c7c7bd;
  --accent: #1f5fa8;          /* course "whale" blue */
  --accent-ink: #ffffff;
  --accent-soft: #e6eef7;
  --eth: #6b7bd6;             /* Ethereum contrast accent */
  --eth-soft: #eceef9;
  --ok: #1f8a4c;
  --ok-soft: #e4f2ea;
  --bad: #c23b3b;
  --bad-soft: #f6e4e4;
  --warn: #b9791f;
  --warn-soft: #f6ecdb;
  /* the cast of parties — reused for badges, arrows, block authorship, fork branches */
  --who-payer: #0f8f8f;   /* Alice, payer */
  --who-payee: #7a52c9;   /* Bob, payee */
  --who-miner: #c07d16;   /* Miner M (won this PoW round) */
  --who-node:  #4d6b8a;   /* honest nodes that validate & relay */
  --who-evil:  #c23b3b;   /* equivocator / double-spender */
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --radius: 10px;
  --radius-sm: 6px;
  --shadow: 0 1px 2px rgba(0,0,0,.06), 0 6px 20px rgba(0,0,0,.06);
  --maxw: 1080px;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #16171a;
    --bg-raised: #202227;
    --bg-sunken: #1a1b1f;
    --ink: #e9e9e6;
    --ink-soft: #b4b4ad;
    --ink-faint: #85857c;
    --line: #32343a;
    --line-strong: #43454d;
    --accent: #6fa8e6;
    --accent-ink: #10243a;
    --accent-soft: #1e2c3d;
    --eth: #9aa7ec;
    --eth-soft: #23263a;
    --ok: #57c98a;
    --ok-soft: #16281f;
    --bad: #e98080;
    --bad-soft: #2e1c1c;
    --warn: #d7a25f;
    --warn-soft: #2c2417;
    --who-payer: #3fb6b6;
    --who-payee: #a98ae0;
    --who-miner: #d9a24e;
    --who-node:  #7f9fc0;
    --who-evil:  #e98080;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 26px rgba(0,0,0,.35);
  }
}

:root[data-theme="dark"] {
  --bg: #16171a;
  --bg-raised: #202227;
  --bg-sunken: #1a1b1f;
  --ink: #e9e9e6;
  --ink-soft: #b4b4ad;
  --ink-faint: #85857c;
  --line: #32343a;
  --line-strong: #43454d;
  --accent: #6fa8e6;
  --accent-ink: #10243a;
  --accent-soft: #1e2c3d;
  --eth: #9aa7ec;
  --eth-soft: #23263a;
  --ok: #57c98a;
  --ok-soft: #16281f;
  --bad: #e98080;
  --bad-soft: #2e1c1c;
  --warn: #d7a25f;
  --warn-soft: #2c2417;
  --who-payer: #3fb6b6;
  --who-payee: #a98ae0;
  --who-miner: #d9a24e;
  --who-node:  #7f9fc0;
  --who-evil:  #e98080;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 8px 26px rgba(0,0,0,.35);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
}

body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 { line-height: 1.25; margin: 0 0 .4em; }
p { margin: 0 0 .8em; }
a { color: var(--accent); }

/* ---------- header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--bg-raised);
  border-bottom: 1px solid var(--line);
}
.site-header__inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 10px 16px;
  display: flex;
  align-items: center;
  gap: 16px;
  flex-wrap: wrap;
}
.brand { display: flex; align-items: center; gap: 10px; margin-right: auto; }
.brand__mark { font-size: 22px; }
.brand__text { display: flex; flex-direction: column; line-height: 1.2; }
.brand__text strong { font-size: 15px; }
.brand__text span { font-size: 12px; color: var(--ink-faint); }

.viewtabs { display: flex; gap: 4px; }
.viewtab {
  text-decoration: none;
  color: var(--ink-soft);
  font-size: 14px;
  font-weight: 600;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
}
.viewtab:hover { background: var(--bg-sunken); }
.viewtab.is-active {
  color: var(--accent);
  background: var(--accent-soft);
  border-color: var(--line);
}

.header-actions { display: flex; gap: 6px; }

/* ---------- buttons ---------- */
.btn {
  font: inherit;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  background: var(--bg-raised);
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  padding: 7px 14px;
  cursor: pointer;
}
.btn:hover { border-color: var(--accent); }
.btn:disabled { opacity: .45; cursor: not-allowed; border-color: var(--line-strong); }
.btn--primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn--primary:hover { filter: brightness(1.06); }
.btn--ghost { background: transparent; border-color: var(--line); color: var(--ink-soft); }
.btn--icon { padding: 7px 10px; }
.btn--sm { padding: 4px 10px; font-size: 13px; }

/* ---------- layout ---------- */
main {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 20px 16px 60px;
}
.view[hidden] { display: none; }

/* ---------- step rail ---------- */
.steprail {
  list-style: none;
  margin: 0 0 18px;
  padding: 0;
  display: flex;
  gap: 6px;
  overflow-x: auto;
  scrollbar-width: thin;
}
.steprail__item {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 7px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--bg-raised);
  color: var(--ink-soft);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
}
.steprail__item:hover { border-color: var(--accent); }
.steprail__item.is-active { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.steprail__num {
  display: inline-grid;
  place-items: center;
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--bg-sunken);
  color: var(--ink-soft);
  font-size: 12px;
}
.steprail__item.is-active .steprail__num { background: rgba(255,255,255,.25); color: #fff; }
.steprail__lec {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: .04em;
  color: var(--ink-faint);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 0 4px;
}
.steprail__item.is-active .steprail__lec { color: #fff; border-color: rgba(255,255,255,.5); }

/* ---------- step card ---------- */
.stepcard {
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 22px;
  min-height: 300px;
}
.step-head { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; margin-bottom: 4px; }
.step-head h2 { font-size: 21px; }
.step-kicker {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--accent);
}
.step-lede { color: var(--ink-soft); max-width: 62ch; }

.stepnav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: 16px;
}
.stepnav__progress { font-size: 13px; color: var(--ink-faint); }

/* ---------- generic panels ---------- */
.panel {
  background: var(--bg-sunken);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 14px;
}
.panel + .panel { margin-top: 12px; }
.panel__title { font-size: 13px; font-weight: 700; color: var(--ink-soft); margin-bottom: 8px; }
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
@media (max-width: 720px) { .grid2, .grid3 { grid-template-columns: 1fr; } }

.field { display: flex; flex-direction: column; gap: 6px; margin-bottom: 12px; }
.field label { font-size: 13px; font-weight: 600; color: var(--ink-soft); }
textarea, input[type="text"], input[type="number"] {
  font: inherit;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--ink);
  background: var(--bg-raised);
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  padding: 8px 10px;
  width: 100%;
  resize: vertical;
}
input[type="range"] { width: 100%; }

.controls { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; margin-bottom: 12px; }

/* ---------- hex / byte rendering ---------- */
.hex {
  font-family: var(--mono);
  font-size: 12px;
  line-height: 1.7;
  word-break: break-all;
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 8px 10px;
}
.hex--label { display: block; font-size: 11px; color: var(--ink-faint); margin-bottom: 3px; font-family: var(--sans); }
.bytes { display: flex; flex-wrap: wrap; gap: 3px; font-family: var(--mono); font-size: 11px; }
.byte {
  padding: 2px 3px;
  border-radius: 3px;
  background: var(--bg-sunken);
  border: 1px solid var(--line);
  color: var(--ink-soft);
}
.byte.is-diff { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); font-weight: 700; }
.byte.is-same { opacity: .5; }

/* ---------- pipeline ---------- */
.pipe { display: flex; flex-wrap: wrap; align-items: stretch; gap: 8px; }
.pipe__stage {
  flex: 1 1 160px;
  min-width: 150px;
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 10px;
}
.pipe__stage h4 { font-size: 12px; color: var(--ink-faint); text-transform: uppercase; letter-spacing: .05em; margin-bottom: 6px; }
.pipe__val { font-family: var(--mono); font-size: 11px; word-break: break-all; color: var(--ink); }
.pipe__op {
  align-self: center;
  font-size: 11px;
  color: var(--ink-faint);
  white-space: nowrap;
  padding: 0 2px;
}
.pipe__op::before { content: "→ "; }
.pipe__op--rev { color: var(--accent); }
.pipe__op--rev::before { content: "⇄ "; }
.pipe__op--rev::after { content: " (reversible)"; opacity: .7; }

/* ---------- callouts ---------- */
.callout {
  border-left: 3px solid var(--line-strong);
  background: var(--bg-sunken);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
  font-size: 14px;
  margin-top: 12px;
}
.callout--eth { border-left-color: var(--eth); background: var(--eth-soft); }
.callout--eth .callout__tag { color: var(--eth); font-weight: 700; }
.callout--note { border-left-color: var(--warn); background: var(--warn-soft); }
.callout__tag { font-weight: 700; margin-right: 6px; }

/* ---------- property cards ---------- */
.props { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
@media (max-width: 720px) { .props { grid-template-columns: 1fr; } }
.prop {
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 10px 12px;
}
.prop h4 { font-size: 13px; margin-bottom: 4px; }
.prop p { font-size: 12.5px; color: var(--ink-soft); margin: 0; }
.prop__link { font-size: 11.5px; color: var(--accent); font-weight: 600; margin-top: 6px; display: block; }

/* ---------- status chips ---------- */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: 12px;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: 999px;
  border: 1px solid var(--line);
}
.chip--ok { background: var(--ok-soft); color: var(--ok); border-color: var(--ok); }
.chip--bad { background: var(--bad-soft); color: var(--bad); border-color: var(--bad); }
.chip--neutral { background: var(--bg-sunken); color: var(--ink-faint); }

/* ---------- collapsible ---------- */
details.disclose {
  margin-top: 12px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--bg-raised);
}
details.disclose > summary {
  cursor: pointer;
  padding: 10px 12px;
  font-size: 13px;
  font-weight: 600;
  color: var(--ink-soft);
}
details.disclose[open] > summary { border-bottom: 1px solid var(--line); }
details.disclose > .disclose__body { padding: 12px; }

/* ---------- stub / in-progress ---------- */
.stub { color: var(--ink-faint); font-size: 14px; }
.stub code { font-family: var(--mono); font-size: 12px; }

/* ---------- concept map (placeholder) ---------- */
.mapcard {
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 22px;
  min-height: 420px;
}

/* ---------- footer ---------- */
.site-footer {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 20px 16px 40px;
  display: flex;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  font-size: 12px;
  color: var(--ink-faint);
  border-top: 1px solid var(--line);
}
.eth-tag { color: var(--eth); font-weight: 700; }

.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

@media (max-width: 560px) {
  body { font-size: 15px; }
  main { padding: 14px 10px 48px; }
  .stepcard { padding: 16px 13px; }
  .step-head h2 { font-size: 19px; }
  .site-header__inner { padding: 8px 10px; gap: 10px; }
  .brand__text span { display: none; }
  .ba__row { flex-wrap: wrap; }
  .ba__row .k { flex-basis: 100%; }
}

/* ---------- cast of parties ---------- */
.castbar {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding: 10px;
  margin-bottom: 14px;
  background: var(--bg-sunken);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
}
.castbar__caption {
  flex-basis: 100%;
  font-size: 11px;
  color: var(--ink-faint);
  margin-bottom: 2px;
}
.who {
  --who: var(--ink-faint);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 4px 9px 4px 4px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--bg-raised);
  font-size: 12px;
  font-weight: 600;
  color: var(--ink-soft);
  cursor: pointer;
  opacity: .5;
}
.who:hover { opacity: .8; }
.who.is-active {
  opacity: 1;
  border-color: var(--who);
  box-shadow: inset 0 -2px 0 var(--who);
}
.who__badge {
  display: inline-grid;
  place-items: center;
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--who);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
}
.who__role { color: var(--ink-faint); font-weight: 500; }
.who.is-active .who__role { color: var(--ink-soft); }

.castbar__detail {
  flex-basis: 100%;
  margin-top: 6px;
  padding: 10px;
  border-radius: var(--radius-sm);
  background: var(--bg-raised);
  border: 1px solid var(--line);
  border-left: 3px solid var(--who, var(--line-strong));
  font-size: 13px;
}
.castbar__detail h4 { font-size: 13px; margin: 0 0 4px; }
.castbar__detail p { margin: 2px 0; color: var(--ink-soft); }
.castbar__detail .lbl { font-weight: 700; color: var(--ink); }

/* ---------- concept cross-links under a step ---------- */
.concepts-foot {
  margin-top: 16px;
  padding-top: 10px;
  border-top: 1px dashed var(--line);
  font-size: 12px;
  color: var(--ink-faint);
}
.concepts-foot a { font-weight: 600; }

/* ---------- before / after on-chain status ---------- */
.ba {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  overflow: hidden;
  margin-top: 12px;
}
.ba__head {
  padding: 8px 12px;
  font-size: 13px;
  font-weight: 700;
  color: var(--ink-soft);
  background: var(--bg-sunken);
  border-bottom: 1px solid var(--line);
}
.ba__cols { display: grid; grid-template-columns: 1fr 1fr; }
@media (max-width: 640px) { .ba__cols { grid-template-columns: 1fr; } }
.ba__col { padding: 12px; }
.ba__col + .ba__col { border-left: 1px solid var(--line); }
@media (max-width: 640px) { .ba__col + .ba__col { border-left: 0; border-top: 1px solid var(--line); } }
.ba__col h5 {
  margin: 0 0 8px;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: .06em;
  color: var(--ink-faint);
}
.ba__col--after h5 { color: var(--ok); }
.ba__row {
  display: flex;
  gap: 8px;
  font-size: 12.5px;
  padding: 3px 0;
  border-bottom: 1px dashed var(--line);
}
.ba__row:last-child { border-bottom: 0; }
.ba__row .k { color: var(--ink-faint); flex: 0 0 92px; }
.ba__row .v { color: var(--ink); font-family: var(--mono); font-size: 12px; }
.ba__note { font-size: 12px; color: var(--ink-soft); margin: 6px 0 0; }