/* Guides: the front page's editorial language (ink on white, hairline rules,
   the compressed display face, colour carried by the app's own art) applied
   to a long-form lesson. One column of reading, figures that are real
   captures of the app with teaching marks drawn over them. */
:root {
  --ink: #212138;
  --ink-soft: rgba(33, 33, 56, 0.62);
  --ink-faint: rgba(33, 33, 56, 0.40);
  --accent: #0085ff;
  --accent-pastel: #a3cffc;
  --hairline: rgba(33, 33, 56, 0.14);
  --page: #ffffff;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, system-ui, "Segoe UI", Roboto, sans-serif;
  font-stretch: extra-condensed;
  color: var(--ink); background: var(--page);
  -webkit-font-smoothing: antialiased;
  line-height: 1.55;
}
h1, h2, h3 { font-weight: 900; letter-spacing: -0.01em; line-height: 1.05; }
a { color: inherit; }
.wrap { max-width: 1020px; margin: 0 auto; padding: 0 28px; }
.kicker {
  font-weight: 800; font-size: 0.78rem; letter-spacing: 0.14em;
  text-transform: uppercase; color: var(--ink-faint); margin-bottom: 14px;
}

/* ---- Header, same as the front page ---- */
header { border-bottom: 1px solid var(--hairline); background: var(--page); }
.nav { display: flex; align-items: baseline; gap: 14px; padding-block: 22px; }
.nav .name { font-weight: 900; font-size: 1.3rem; letter-spacing: -0.01em; text-decoration: none; }
.nav .spacer { flex: 1; }
.nav .waver { height: 46px; width: auto; align-self: baseline; margin-left: -8px; translate: 0 14px; transform-origin: 50% 100%; }
@keyframes cat-wave {
  0%, 78%, 100% { transform: rotate(0deg); }
  82% { transform: rotate(-7deg); } 86% { transform: rotate(5deg); }
  90% { transform: rotate(-4deg); } 94% { transform: rotate(2deg); }
}
.nav .waver { animation: cat-wave 7s ease-in-out infinite; }
.nav a.cta {
  text-decoration: none; font-weight: 800; font-size: 0.78rem;
  letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-soft);
}
.nav a.cta:hover { color: var(--accent); }

/* ---- Article ---- */
.lede-block { padding-block: 72px 36px; } /* padding-block only: the shorthand zeroed .wrap's side padding */
.lede-block h1 { font-size: clamp(2.6rem, 7vw, 4.4rem); max-width: 14ch; }
.lede-block .lede {
  font-size: clamp(1.05rem, 2.6vw, 1.25rem); color: var(--ink-soft);
  font-weight: 600; max-width: 52ch; margin-top: 18px;
}
.lede-block .meta { margin-top: 18px; color: var(--ink-faint); font-weight: 700; font-size: 0.9rem; }
article section { border-top: 1px solid var(--hairline); padding: 64px 0; }
article h2 { font-size: clamp(1.7rem, 4vw, 2.4rem); max-width: 22ch; }
article p { max-width: 62ch; font-size: 1.08rem; font-weight: 500; color: var(--ink); margin-top: 16px; }
article p.soft { color: var(--ink-soft); font-weight: 600; }
article ul { max-width: 62ch; margin-top: 14px; padding-left: 1.2em; font-size: 1.08rem; font-weight: 500; }
article li { margin-top: 6px; }
article li b { font-weight: 900; }
.rule {
  margin-top: 22px; padding: 18px 22px; border-left: 4px solid var(--accent);
  background: rgba(163, 207, 252, 0.18); border-radius: 0 14px 14px 0;
  font-weight: 800; font-size: 1.15rem; max-width: 60ch;
}

/* ---- Figures: real captures, marks drawn over them ---- */
.fig { margin-top: 34px; }
.fig .frame {
  position: relative; width: min(560px, 100%); margin: 0 auto;
  border-radius: 24px; overflow: hidden;
  border: 1px solid var(--hairline);
  box-shadow: 0 18px 40px rgba(33, 33, 56, 0.10);
  background: #fff;
}
.fig .frame img { display: block; width: 100%; height: auto; }
.fig .frame svg { position: absolute; inset: 0; width: 100%; height: 100%; pointer-events: none; }
.fig figcaption {
  margin: 14px auto 0; max-width: 52ch; text-align: center;
  color: var(--ink-soft); font-weight: 600; font-size: 0.98rem; line-height: 1.45;
}
.fig.phone .frame { width: min(340px, 82vw); border-radius: 30px; }
/* Three boards side by side: rows, columns, boxes */
.trio { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: 34px; }
.trio .fig { margin-top: 0; }
.trio .fig .frame { border-radius: 18px; }
.trio figcaption { font-size: 0.92rem; }

/* Step-through: a stack of frames, one showing, a caption per frame,
   dots to show where you are. Tap the figure or use the arrows. */
.steps .frame { cursor: pointer; }
.steps .frames { position: relative; }
.steps .frames .f { position: relative; }
.steps .frames .f:not(:first-child) { position: absolute; inset: 0; }
.steps .frames .f { opacity: 0; transition: opacity 0.28s ease; }
.steps .frames .f.on { opacity: 1; }
.steps .frames .f:first-child { opacity: 1; } /* static fallback before JS runs */
.steps.js .frames .f:first-child:not(.on) { opacity: 0; }
.steps .ctl { display: flex; align-items: center; justify-content: center; gap: 12px; margin-top: 14px; }
.steps .ctl button {
  appearance: none; border: 1px solid var(--hairline); background: #fff; color: var(--ink);
  width: 38px; height: 38px; border-radius: 50%; font-size: 1.1rem; font-weight: 900; cursor: pointer;
  transition: transform 0.15s ease, background 0.15s ease;
}
.steps .ctl button:hover { background: var(--accent-pastel); }
.steps .ctl button:active { transform: scale(0.94); }
.steps .ctl .dots { display: flex; gap: 8px; }
.steps .ctl .dots i { width: 8px; height: 8px; border-radius: 50%; background: var(--hairline); transition: background 0.2s ease, transform 0.2s ease; }
.steps .ctl .dots i.on { background: var(--accent); transform: scale(1.25); }
.steps figcaption { min-height: 3.2em; }
.steps figcaption .step { font-weight: 900; color: var(--ink); margin-right: 6px; }

/* Marks over the board */
.mk-ring { fill: none; stroke: var(--accent); stroke-width: 9; }
.mk-cand { fill: none; stroke: var(--ink); stroke-width: 6; stroke-dasharray: 14 10; opacity: 0.7; }
.mk-x { stroke: var(--ink); stroke-width: 10; stroke-linecap: round; opacity: 0.55; }
.mk-src { fill: none; stroke: var(--ink); stroke-width: 8; opacity: 0.8; }

/* ---- Try it ---- */
.cta-block { border-top: 1px solid var(--hairline); padding: 72px 0 96px; text-align: center; }
.cta-block h2 { font-size: clamp(1.9rem, 4.6vw, 2.8rem); margin: 0 auto; }
.cta-block p { color: var(--ink-soft); font-weight: 600; font-size: 1.08rem; max-width: 46ch; margin: 16px auto 0; }
.applink {
  display: inline-block; margin-top: 28px;
  background: var(--accent-pastel); color: var(--ink);
  font-weight: 800; font-size: 1rem; text-decoration: none;
  padding: 14px 28px; border-radius: 15px;
  box-shadow: 0 4px 8px rgba(0,0,0,0.15);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.applink:hover { transform: translateY(-2px); box-shadow: 0 7px 14px rgba(0,0,0,0.16); }
.applink:active { transform: scale(0.97); }

footer { border-top: 1px solid var(--hairline); padding: 34px 0 56px; }
.foot { display: flex; flex-wrap: wrap; align-items: baseline; gap: 22px; color: var(--ink-soft); font-weight: 700; font-size: 0.92rem; }
.foot .name { font-weight: 900; color: var(--ink); font-size: 1.05rem; }
.foot a { text-decoration: none; }
.foot a:hover { color: var(--accent); }
.foot .fine { margin-left: auto; color: var(--ink-faint); font-weight: 600; }

@media (prefers-reduced-motion: reduce) {
  .nav .waver { animation: none; }
  .steps .frames .f { transition: none; }
}
@media (max-width: 760px) {
  .nav .waver { height: 36px; translate: 0 11px; }
  .lede-block { padding-block: 48px 24px; }
  article section { padding: 48px 0; }
  .trio { grid-template-columns: 1fr; gap: 26px; }
  .trio .fig .frame { width: min(420px, 100%); }
  .foot .fine { margin-left: 0; }
}

/* Questions: a smaller heading per question, same column */
article h3 { font-size: 1.2rem; margin-top: 26px; max-width: 40ch; }
article h3 + p { margin-top: 8px; }

/* More marks (all guides): a tinted band over a run of cells, and arrows */
.mk-band { fill: var(--accent); opacity: 0.16; }
.mk-arrow { stroke: var(--ink); stroke-width: 8; stroke-linecap: round; opacity: 0.8; fill: none; }
.mk-head { fill: var(--ink); opacity: 0.8; }