/* TRUSS — public landing page.
   No build step, no framework, no CDN, no webfont. Everything here is either a
   system font or a colour. The page must render identically on a machine with
   no route to the internet, because some of the people it is written for will
   be reading it on exactly such a machine. */

/* ── tokens ─────────────────────────────────────────────────────────────── */
:root {
  --bg:       #fbfbfa;
  --bg-alt:   #f2f2f0;
  --card:     #ffffff;
  --ink:      #14171a;
  --ink-2:    #4b535b;
  --ink-3:    #6f7880;
  --rule:     #dcdedb;
  --rule-2:   #c3c7c3;
  --accent:   #0b56a4;
  --on-accent:#ffffff;

  --sans: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
          "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
          "Liberation Mono", "DejaVu Sans Mono", monospace;

  --pad: clamp(1.25rem, 5vw, 3.25rem);
  --max: 74rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:       #0b0d0f;
    --bg-alt:   #111417;
    --card:     #14181b;
    --ink:      #e9ecee;
    --ink-2:    #a6aeb5;
    --ink-3:    #7d868d;
    --rule:     #22272b;
    --rule-2:   #333a3f;
    --accent:   #74b4ff;
    --on-accent:#07121f;
  }
}

/* ── reset ──────────────────────────────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; }
html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  scroll-behavior: smooth;
}
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 1rem;
  line-height: 1.55;
  /* A long identifier or a URL must wrap rather than push the viewport wide.
     This is the whole no-horizontal-scroll story on a phone. */
  overflow-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 { margin: 0; font-weight: 640; letter-spacing: -0.014em; line-height: 1.15; }
p, ol, ul, dl { margin: 0; }
a { color: var(--accent); text-underline-offset: 0.18em; }
b, strong { font-weight: 650; color: var(--ink); }
/* Emphasis by weight and colour, never by underline: this page carries real
   links in running text and a decorative underline reads as one. */
em { font-style: normal; font-weight: 640; color: var(--ink); }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

.skip {
  position: absolute; left: -9999px;
  background: var(--accent); color: var(--on-accent);
  padding: 0.6rem 1rem; font: 600 0.85rem/1 var(--mono); z-index: 10;
}
.skip:focus { left: 0.5rem; top: 0.5rem; }

.wrap { max-width: var(--max); margin-inline: auto; padding-inline: var(--pad); }

/* ── masthead ───────────────────────────────────────────────────────────── */
.masthead { border-bottom: 1px solid var(--rule); background: var(--bg); }
.masthead-in {
  display: flex; align-items: baseline; justify-content: space-between;
  gap: 1rem; padding-block: 1.1rem;
}
.mark {
  font: 700 1.05rem/1 var(--mono);
  letter-spacing: 0.24em;
}
.mark-sub {
  font: 400 0.72rem/1 var(--mono);
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink-3);
}

/* ── hero ───────────────────────────────────────────────────────────────── */
.hero { padding-block: clamp(3rem, 9vw, 6.5rem) clamp(2.5rem, 6vw, 4.5rem); }

.eyebrow {
  font: 500 0.74rem/1.3 var(--mono);
  letter-spacing: 0.17em; text-transform: uppercase; color: var(--accent);
  margin-bottom: 1.4rem;
}

.hero h1 {
  font-size: clamp(2.05rem, 6.2vw, 3.9rem);
  line-height: 1.04;
  letter-spacing: -0.028em;
  max-width: 21ch;
}

.lede {
  margin-top: 1.6rem;
  max-width: 64ch;
  font-size: clamp(1rem, 0.97rem + 0.2vw, 1.12rem);
  color: var(--ink-2);
}
.lede.narrow { max-width: 58ch; }

.stats {
  list-style: none; padding: 0;
  margin-top: clamp(2.25rem, 5vw, 3.25rem);
  display: grid; gap: 0 clamp(1.5rem, 4vw, 3.5rem);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 12rem), 1fr));
}
.stats li { border-top: 2px solid var(--ink); padding-top: 0.7rem; }
.stats b {
  display: block; font: 600 2.1rem/1 var(--mono);
  letter-spacing: -0.02em; color: var(--accent);
}
.stats span {
  display: block; margin-top: 0.4rem; max-width: 22ch;
  font: 400 0.76rem/1.4 var(--mono);
  letter-spacing: 0.03em; color: var(--ink-3);
}

/* ── bands ──────────────────────────────────────────────────────────────── */
.band {
  border-top: 1px solid var(--rule);
  padding-block: clamp(2.75rem, 7vw, 5rem);
}
.band.alt { background: var(--bg-alt); }

.sec {
  font: 500 0.72rem/1 var(--mono);
  letter-spacing: 0.17em; text-transform: uppercase; color: var(--accent);
  margin-bottom: 1.1rem;
}
.band h2 {
  font-size: clamp(1.45rem, 1.15rem + 1.5vw, 2.15rem);
  max-width: 26ch;
}
.band h3 {
  font-size: 1rem;
  letter-spacing: -0.006em;
}

/* ── 01 the loop ────────────────────────────────────────────────────────── */
.steps {
  list-style: none; padding: 0;
  margin-top: clamp(2rem, 4.5vw, 3rem);
  counter-reset: step;
  display: grid; gap: 1.75rem clamp(1.5rem, 3.5vw, 3rem);
  /* 14rem so that all FOUR steps sit on one row on a desktop — the loop reads
     as a sequence, and a 3 + 1 wrap breaks the reading of it. */
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 14rem), 1fr));
}
.steps li { counter-increment: step; border-top: 1px solid var(--rule-2); padding-top: 0.9rem; }
.steps li::before {
  content: counter(step, decimal-leading-zero);
  display: block; margin-bottom: 0.55rem;
  font: 500 0.76rem/1 var(--mono); letter-spacing: 0.12em; color: var(--ink-3);
}
.steps p { margin-top: 0.5rem; color: var(--ink-2); font-size: 0.94rem; }

/* ── 02 invariants ──────────────────────────────────────────────────────── */
.rule-quote {
  margin-top: 1.5rem; max-width: 56ch;
  padding-left: 1rem; border-left: 3px solid var(--accent);
  font-size: 1.02rem; color: var(--ink);
}
.inv {
  list-style: none; padding: 0;
  margin-top: clamp(2rem, 4.5vw, 3rem);
  counter-reset: inv;
  display: grid; gap: 1.6rem clamp(1.5rem, 3.5vw, 3rem);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 18rem), 1fr));
}
.inv li {
  counter-increment: inv;
  display: grid; grid-template-columns: 2.15rem 1fr; align-items: start;
  border-top: 1px solid var(--rule-2); padding-top: 0.85rem;
}
.inv li::before {
  content: counter(inv);
  font: 600 1.05rem/1.25 var(--mono); color: var(--accent);
}
.inv p { margin-top: 0.35rem; grid-column: 2; color: var(--ink-2); font-size: 0.94rem; }

/* ── 03 cards ───────────────────────────────────────────────────────────── */
.cards {
  margin-top: clamp(2rem, 4.5vw, 3rem);
  display: grid; gap: clamp(1rem, 2.5vw, 1.5rem);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 19rem), 1fr));
}
.card {
  background: var(--card);
  border: 1px solid var(--rule-2);
  padding: clamp(1.25rem, 2.5vw, 1.75rem);
}
.cardno {
  font: 600 0.78rem/1 var(--mono);
  letter-spacing: 0.2em; text-transform: uppercase; color: var(--accent);
  margin-bottom: 0.9rem;
}
.card h3 { font-size: 1.08rem; }
.card p + p { margin-top: 0.85rem; }
.card p:not(.cardno) { color: var(--ink-2); font-size: 0.93rem; }
.card h3 + p { margin-top: 0.7rem; }

/* ── 04 runtime grid ────────────────────────────────────────────────────── */
.grid2 {
  margin-top: clamp(2rem, 4.5vw, 3rem);
  display: grid; gap: 1.7rem clamp(1.5rem, 3.5vw, 3rem);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 17rem), 1fr));
}
.item { border-top: 1px solid var(--rule-2); padding-top: 0.9rem; }
.item p { margin-top: 0.5rem; color: var(--ink-2); font-size: 0.94rem; }

/* ── 05 tiers ───────────────────────────────────────────────────────────── */
.tiers {
  margin-top: clamp(2rem, 4.5vw, 3rem);
  display: grid;
  grid-template-columns: minmax(0, 15rem) minmax(0, 1fr);
  column-gap: clamp(1.5rem, 3.5vw, 3rem);
}
.tiers dt {
  border-top: 1px solid var(--rule-2);
  padding: 0.95rem 0;
  font: 600 1rem/1.4 var(--sans);
  display: flex; align-items: center; gap: 0.6rem; flex-wrap: wrap;
}
.tiers dd {
  border-top: 1px solid var(--rule-2);
  padding: 0.95rem 0;
  margin: 0; color: var(--ink-2); font-size: 0.94rem;
}
.tcode {
  font: 600 0.72rem/1 var(--mono); letter-spacing: 0.1em;
  color: var(--accent); border: 1px solid var(--accent);
  padding: 0.28rem 0.42rem;
}

@media (max-width: 44rem) {
  .tiers { grid-template-columns: minmax(0, 1fr); }
  .tiers dt { padding-bottom: 0.35rem; }
  .tiers dd { border-top: 0; padding-top: 0; padding-bottom: 1.1rem; }
}

.note {
  margin-top: clamp(1.75rem, 3.5vw, 2.5rem);
  max-width: 62ch; padding-top: 1rem;
  border-top: 2px solid var(--ink);
  color: var(--ink-2); font-size: 0.94rem;
}

/* ── 06 cta ─────────────────────────────────────────────────────────────── */
.cta .btn {
  display: inline-block; margin-top: 1.9rem;
  background: var(--accent); color: var(--on-accent);
  padding: 0.85rem 1.6rem; text-decoration: none;
  font: 600 0.82rem/1 var(--mono); letter-spacing: 0.13em; text-transform: uppercase;
}
.cta .btn:hover { filter: brightness(1.12); }
.btn-note {
  display: inline-block; margin-left: 1rem;
  font: 400 0.82rem/1 var(--mono); color: var(--ink-3);
}

/* ── footer ─────────────────────────────────────────────────────────────── */
.foot { border-top: 1px solid var(--rule); padding-block: 2.25rem 3rem; }
.foot-in {
  display: flex; flex-wrap: wrap; gap: 0.5rem 2.5rem;
  font: 400 0.78rem/1.55 var(--mono); color: var(--ink-3);
}
.foot p { max-width: 52ch; }