/* mosslogicllc.com — one stylesheet.
   Brand is not decided yet (docs/decisions.md). Everything visual is a token
   on :root, so a brand kit later means editing this block and nothing else.
   Two faces: Fraunces for display, IBM Plex Sans for text. */

:root {
  --ink: #171a19;
  --ink-soft: #4e564f;
  --ink-faint: #606861;
  --paper: #f7f6f2;
  --paper-raised: #fffefb;
  --rule: #d9d6cc;
  --accent: #39624b;
  --accent-soft: #e4ece6;
  --negative: #8c3a2c;

  --display: Fraunces, Georgia, "Times New Roman", serif;
  --text: "IBM Plex Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;

  --measure: 68ch;
  --gutter: clamp(16px, 5vw, 56px);
  --step: clamp(44px, 7vw, 88px);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink: #e9e7e0;
    --ink-soft: #a9b0a9;
    --ink-faint: #979f98;
    --paper: #121413;
    --paper-raised: #1a1d1b;
    --rule: #2e332f;
    --accent: #8ebfa3;
    --accent-soft: #1f2a24;
    --negative: #e09185;
  }
}

:root[data-theme="dark"] {
  --ink: #e9e7e0;
  --ink-soft: #a9b0a9;
  --ink-faint: #979f98;
  --paper: #121413;
  --paper-raised: #1a1d1b;
  --rule: #2e332f;
  --accent: #8ebfa3;
  --accent-soft: #1f2a24;
  --negative: #e09185;
}

*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--text);
  font-size: 17px;
  line-height: 1.65;
  font-synthesis: none;
  overflow-x: hidden;
}

.wrap { max-width: 1140px; margin-inline: auto; padding-inline: var(--gutter); }

.skip { position: absolute; left: -9999px; }
.skip:focus {
  left: 12px; top: 12px; z-index: 10;
  background: var(--paper-raised); color: var(--ink);
  padding: 12px 16px; border: 1px solid var(--ink);
}

:where(a) { color: inherit; text-decoration-color: var(--accent); text-underline-offset: 4px; }
:where(a):hover { text-decoration-thickness: 2px; }
:where(a):focus-visible, :where(button, input, select, textarea):focus-visible {
  outline: 2px solid var(--accent); outline-offset: 3px;
}

/* ------------------------------------------------------------- masthead */

.masthead {
  display: flex; align-items: center; gap: 24px; flex-wrap: wrap;
  padding: 20px var(--gutter);
  border-bottom: 1px solid var(--rule);
}

.brand {
  font-family: var(--display);
  font-size: 25px; font-weight: 600; letter-spacing: -0.02em;
  line-height: 1; text-decoration: none;
}
.brand span {
  display: block; margin-top: 6px;
  font-family: var(--text); font-size: 10px; font-weight: 400;
  letter-spacing: 0.18em; text-transform: uppercase; color: var(--ink-faint);
}

.nav { margin-left: auto; display: flex; align-items: center; gap: 22px; flex-wrap: wrap; }
.nav a {
  font-size: 14.5px; text-decoration: none;
  padding-block: 4px; border-bottom: 2px solid transparent;
}
.nav a:hover { border-bottom-color: var(--rule); }
.nav a[aria-current="page"] { border-bottom-color: var(--accent); }

.btn {
  display: inline-block; padding: 12px 20px;
  font-size: 15px; text-decoration: none; border: 1px solid var(--ink);
  background: transparent; color: var(--ink); cursor: pointer;
  font-family: var(--text);
}
.btn-primary { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.btn-primary:hover { background: var(--accent); border-color: var(--accent); color: #fff; }
.nav-cta { padding: 9px 16px; border-bottom-width: 1px; }
.btn[disabled] { opacity: 0.5; cursor: default; }

/* ------------------------------------------------------------- sections */

.hero { padding-block: clamp(40px, 7vw, 86px) var(--step); }
.section { padding-block: var(--step); border-top: 1px solid var(--rule); }

h1, h2, h3 { font-family: var(--display); font-weight: 500; letter-spacing: -0.025em; }

h1 {
  font-size: clamp(2.3rem, 6vw, 3.9rem);
  line-height: 1.04; margin: 0 0 24px; max-width: 24ch;
}
h2 {
  font-size: clamp(1.65rem, 3.6vw, 2.3rem);
  line-height: 1.14; margin: 0 0 24px; max-width: 30ch;
}
h3 { font-size: 1.17rem; line-height: 1.35; margin: 0 0 8px; }
/* A sub-heading that follows other content needs air above it. */
.wrap > * + h3 { margin-top: 34px; }

p, ul, ol { max-width: var(--measure); }
p { margin: 0 0 20px; color: var(--ink-soft); }
.hero > .wrap > p:first-of-type { font-size: 1.16rem; color: var(--ink); }

h2 + p, h2 + .point { margin-top: -4px; }

/* A paragraph that opens with a bold lead-in is one point in a list of them. */
.point { margin: 0 0 18px; }
.point strong {
  font-family: var(--display); font-weight: 600; font-size: 1.06em;
  color: var(--ink); letter-spacing: -0.015em;
}

ul, ol { margin: 0 0 22px; padding-left: 1.3em; color: var(--ink-soft); }
li { margin-block: 7px; }
li::marker { color: var(--ink-faint); }

strong { color: var(--ink); font-weight: 600; }
code {
  font-family: ui-monospace, "SF Mono", Menlo, monospace; font-size: 0.88em;
  background: var(--accent-soft); padding: 1px 5px; border-radius: 2px;
}
abbr { text-decoration: none; color: var(--accent); }

.eyebrow {
  font-size: 11px; letter-spacing: 0.17em; text-transform: uppercase;
  color: var(--ink-faint); margin: 0 0 16px;
}
.mini { font-size: 13px; line-height: 1.55; color: var(--ink-faint); margin: 0 0 8px; }

/* ---------------------------------------------------------------- tables */

.tablewrap { overflow-x: auto; margin: 0 0 24px; border: 1px solid var(--rule); }
table { width: 100%; border-collapse: collapse; font-size: 14.5px; min-width: 520px; }
th, td { text-align: left; padding: 13px 16px; border-bottom: 1px solid var(--rule); vertical-align: top; }
thead th {
  font-family: var(--text); font-weight: 600; font-size: 12px;
  letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-faint);
  background: var(--paper-raised);
}
tbody th { font-weight: 600; color: var(--ink); white-space: nowrap; }
tbody tr:last-child th, tbody tr:last-child td { border-bottom: 0; }

/* -------------------------------------------------------------- diagrams */

.diagram { margin: 0; }
.diagram figcaption {
  margin-top: 14px; font-size: 11px; letter-spacing: 0.12em;
  text-transform: uppercase; color: var(--ink-faint);
}
.diagram-svg { width: 100%; height: auto; display: block; color: var(--ink-faint); }
.dg-box rect { fill: var(--paper-raised); stroke: var(--rule); stroke-width: 1.2; }
.dg-memory { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.4; }
.dg-line { fill: none; stroke: var(--ink-faint); stroke-width: 1.2; }
.dg-label {
  fill: var(--ink-soft); font-family: var(--text); font-size: 13px;
  letter-spacing: 0.01em;
}
.dg-memory-title {
  fill: var(--ink); font-family: var(--display); font-size: 21px; font-weight: 600;
}

/* Home hero: text left, diagram right, stacked on narrow screens. */
.hero:has(.hero-text) > .wrap {
  display: grid; grid-template-columns: 1.1fr 0.9fr;
  gap: clamp(28px, 5vw, 64px); align-items: center;
}
.hero-text > :last-child { margin-bottom: 0; }
.hero-text > p.point { margin-bottom: 22px; }

.walls-cols {
  list-style: none; padding: 0; margin: 0 0 4px; max-width: none;
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px;
}
.walls-cols li {
  margin: 0; padding: 20px; border: 1px solid var(--rule);
  background: var(--paper-raised);
}
.walls-n { font-size: 11px; letter-spacing: 0.14em; color: var(--ink-faint); }
.walls-cols h3 { margin: 12px 0 8px; font-size: 1.06rem; }
.walls-cols p { margin: 0; font-size: 14px; max-width: none; }

/* ------------------------------------------------------------ calculator */

.calc {
  display: grid; grid-template-columns: 1fr 1fr;
  gap: clamp(20px, 3vw, 40px); margin: 8px 0 32px; align-items: start;
}
.calc-inputs, .calc-outputs {
  border: 1px solid var(--rule); background: var(--paper-raised); padding: clamp(18px, 2.5vw, 28px);
}
.calc-outputs { background: var(--accent-soft); border-color: var(--accent); }

.ctrl { margin-bottom: 20px; }
.ctrl:last-child { margin-bottom: 4px; }
.ctrl label {
  display: flex; justify-content: space-between; align-items: baseline; gap: 12px;
  font-size: 13.5px; color: var(--ink-soft); margin-bottom: 8px;
}
.ctrl output {
  font-family: var(--display); font-size: 1.15rem; font-weight: 600;
  color: var(--ink); white-space: nowrap;
}
input[type="range"] { width: 100%; accent-color: var(--accent); margin: 0; }

select, input[type="text"], input[type="email"], input:not([type]), textarea {
  width: 100%; font: inherit; font-size: 15px; color: var(--ink);
  background: var(--paper); border: 1px solid var(--rule); border-radius: 0;
  padding: 11px 12px;
}
select { cursor: pointer; }
textarea { resize: vertical; min-height: 120px; }

.out {
  display: flex; justify-content: space-between; align-items: baseline; gap: 16px;
  padding: 11px 0; border-bottom: 1px solid color-mix(in srgb, var(--accent) 25%, transparent);
}
.out-k { font-size: 13.5px; color: var(--ink-soft); }
.out-v {
  font-family: var(--display); font-size: 1.22rem; font-weight: 600;
  color: var(--ink); text-align: right; white-space: nowrap;
}
.out-v.is-negative { color: var(--negative); }
.calc-outputs .eyebrow { margin-top: 20px; }
.calc-outputs .eyebrow:first-child { margin-top: 0; }
.calc-outputs .mini { margin-top: 14px; }

/* ------------------------------------------------------------------ form */

.form {
  border: 1px solid var(--rule); background: var(--paper-raised);
  padding: clamp(20px, 3vw, 32px); max-width: 640px;
}
.row { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.field { margin-bottom: 18px; }
.field label { display: block; font-size: 13.5px; color: var(--ink-soft); margin-bottom: 7px; }
.opt { color: var(--ink-faint); }
.trap { position: absolute; left: -9999px; width: 1px; height: 1px; overflow: hidden; }

.form-status { margin: 16px 0 0; font-size: 14px; min-height: 1.4em; }
.form-status.is-ok { color: var(--accent); }
.form-status.is-error, .form-status.is-warn { color: var(--negative); }

/* ---------------------------------------------------------------- footer */

.footer {
  border-top: 1px solid var(--rule); padding: 28px var(--gutter) 40px;
  display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap;
  font-size: 13px; color: var(--ink-faint);
}
.footer p { margin: 0; color: inherit; max-width: none; }
.footer-links { display: flex; gap: 20px; flex-wrap: wrap; }

/* ------------------------------------------------------------ narrow ----- */

@media (max-width: 880px) {
  .calc, .row { grid-template-columns: 1fr; }
  .walls-cols { grid-template-columns: 1fr 1fr; }
  .hero:has(.hero-text) > .wrap { grid-template-columns: 1fr; }
  .hero:has(.hero-text) > .wrap > .diagram { max-width: 480px; }
}

@media (max-width: 600px) {
  body { font-size: 16.5px; }
  .masthead { gap: 14px; }
  .nav { margin-left: 0; width: 100%; gap: 16px; }
  .nav a { font-size: 13.5px; }
  .walls-cols { grid-template-columns: 1fr; }
  h1 { max-width: none; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
}