/* A4 Labs site. Editorial "ledger" direction: navy ink on warm paper, teal for numbers that tie out, amber for gaps. */

:root {
  --ink: #0f2747;
  --ink-soft: #33415c;
  --muted: #5b6680;
  --paper: #f7f5f0;
  --paper-deep: #efece4;
  --card: #ffffff;
  --line: #e2ddd2;
  --teal: #14b8a6;
  --teal-text: #0b7a6e;
  --amber: #8f5300;
  --amber-bg: #fdf1dc;
  --navy-deep: #011c41;

  --font-sans: "Instrument Sans", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "Cascadia Mono", Consolas, monospace;

  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.0625rem);
  --text-lead: clamp(1.125rem, 1rem + 0.6vw, 1.375rem);
  --text-h2: clamp(1.75rem, 1.2rem + 2.2vw, 2.75rem);
  --text-hero: clamp(2.5rem, 1.4rem + 5vw, 5rem);

  --space-section: clamp(4rem, 3rem + 5vw, 8rem);
  --radius: 14px;
  --radius-small: 8px;
  --gutter: clamp(1rem, 0.5rem + 2.5vw, 2.5rem);

  --duration-fast: 150ms;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

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

/* Author display rules would otherwise override the hidden attribute. */
[hidden] { display: none !important; }

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

/* Keep anchor targets and focused fields clear of the sticky header. */
html { scroll-behavior: smooth; scroll-padding-top: 5rem; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--ink);
  background-color: var(--paper);
  /* Faint graph-paper texture */
  background-image:
    linear-gradient(var(--paper-deep) 1px, transparent 1px),
    linear-gradient(90deg, var(--paper-deep) 1px, transparent 1px);
  background-size: 32px 32px;
}

img { max-width: 100%; display: block; }

h1, h2, h3 { line-height: 1.1; letter-spacing: -0.02em; margin: 0 0 0.6em; }
h1 { font-size: var(--text-hero); font-weight: 700; letter-spacing: -0.035em; }
h2 { font-size: var(--text-h2); font-weight: 650; max-width: 22ch; }
h3 { font-size: 1.2rem; font-weight: 650; }
p { margin: 0 0 1em; }

a { color: inherit; }

.mono { font-family: var(--font-mono); font-feature-settings: "tnum" 1; letter-spacing: -0.01em; }

.wrap { width: 100%; max-width: 1180px; margin: 0 auto; padding: 0 var(--gutter); }

.skip-link {
  position: absolute; left: 1rem; top: -3rem; z-index: 20;
  background: var(--ink); color: #fff; padding: 0.5rem 1rem; border-radius: var(--radius-small);
}
.skip-link:focus { top: 1rem; }

:focus-visible { outline: 3px solid var(--ink); outline-offset: 3px; border-radius: 4px; }
.section-ink :focus-visible, .card-ink :focus-visible { outline-color: var(--teal); }

.eyebrow {
  font-family: var(--font-mono); font-size: 0.8rem; font-weight: 600;
  letter-spacing: 0.12em; text-transform: uppercase; color: var(--teal-text); margin-bottom: 1rem;
}

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 0.5rem;
  min-height: 48px; padding: 0.75rem 1.4rem; border-radius: 999px;
  background: var(--ink); color: #fff; font-weight: 600; text-decoration: none;
  border: 2px solid var(--ink);
  transition: transform var(--duration-fast) var(--ease-out), background-color var(--duration-fast), box-shadow var(--duration-fast);
}
.btn:hover { transform: translateY(-2px); box-shadow: 0 6px 0 -2px var(--teal); }
.btn:active { transform: translateY(0); box-shadow: none; }
.btn-small { min-height: 40px; padding: 0.5rem 1rem; font-size: 0.95rem; }
.btn-ghost { background: transparent; color: var(--ink); }
.btn-ghost:hover { background: var(--card); }
.btn-light { background: #fff; color: var(--ink); border-color: #fff; }

/* Header */
.site-header {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.header-row { display: flex; align-items: center; justify-content: space-between; min-height: 68px; gap: 1rem; }
.brand { display: inline-flex; align-items: center; gap: 0.6rem; font-weight: 700; font-size: 1.15rem; text-decoration: none; }
.brand img { border-radius: 8px; }
.nav { display: flex; align-items: center; gap: 1.5rem; }
.nav a:not(.btn) { text-decoration: none; color: var(--ink-soft); font-weight: 500; position: relative; }
.nav a:not(.btn)::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -4px; height: 2px;
  background: var(--teal); transform: scaleX(0); transform-origin: left; transition: transform var(--duration-fast) var(--ease-out);
}
.nav a:not(.btn):hover::after { transform: scaleX(1); }

/* Hero */
.hero { padding: clamp(3rem, 2rem + 5vw, 6.5rem) 0 var(--space-section); }
.hero-grid { display: grid; grid-template-columns: 1.15fr 0.85fr; gap: clamp(2rem, 1rem + 4vw, 5rem); align-items: center; }
.lead { font-size: var(--text-lead); color: var(--ink-soft); max-width: 36ch; }
.cta-row { display: flex; flex-wrap: wrap; gap: 0.75rem; margin: 2rem 0 2.5rem; }
.proof-points { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.5rem; }
.proof-points li { font-family: var(--font-mono); font-size: 0.9rem; color: var(--ink-soft); padding-left: 1.6rem; position: relative; }
.proof-points li::before { content: "→"; position: absolute; left: 0; color: var(--teal-text); }

/* Ledger card (hero visual) */
.ledger {
  margin: 0; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.6rem; box-shadow: 0 1px 0 var(--line), 14px 14px 0 -1px var(--ink);
  transform: rotate(-1.2deg);
  transition: transform 400ms var(--ease-out);
}
.ledger:hover { transform: rotate(0deg); }
.ledger-head { display: flex; justify-content: space-between; align-items: center; font-size: 0.85rem; color: var(--muted); margin-bottom: 1rem; }
.tag { font-family: var(--font-mono); font-size: 0.75rem; font-weight: 600; padding: 0.2rem 0.6rem; border-radius: 999px; }
.tag-warn { background: var(--amber-bg); color: var(--amber); }
.ledger-figure { font-size: clamp(2rem, 1.5rem + 2vw, 2.75rem); font-weight: 600; margin: 0; }
.ledger-sub { color: var(--muted); font-size: 0.9rem; margin-bottom: 1.4rem; }

.tier-track { position: relative; height: 14px; background: var(--paper-deep); border-radius: 999px; margin: 2.2rem 0 1.4rem; }
.tier-fill { position: absolute; inset: 0 auto 0 0; width: 83.6%; background: linear-gradient(90deg, var(--ink), var(--ink-soft)); border-radius: 999px; }
.tier-mark { position: absolute; top: -8px; bottom: -8px; width: 2px; background: var(--ink); }
.tier-mark span { position: absolute; bottom: calc(100% + 4px); transform: translateX(-50%); white-space: nowrap; font-family: var(--font-mono); font-size: 0.7rem; color: var(--muted); }
.tier-mark-1 { left: 45.45%; }
.tier-mark-2 { left: 90.9%; background: var(--amber); }
.tier-mark-2 span { color: var(--amber); font-weight: 600; transform: translateX(-80%); }
.ledger-gap { font-size: 0.95rem; color: var(--ink-soft); }
.ledger-gap strong { color: var(--ink); }

.recon { margin: 1.2rem 0 0; border-top: 1px dashed var(--line); padding-top: 1rem; display: grid; gap: 0.4rem; }
.recon div, .calc-out dl div { display: flex; justify-content: space-between; gap: 1rem; font-size: 0.9rem; }
.recon dt, .calc-out dt { color: var(--muted); }
.recon dd, .calc-out dd { margin: 0; font-weight: 600; }
.ok { color: var(--teal-text); }
.ledger-note { margin-top: 1rem; font-size: 0.75rem; color: var(--muted); }

/* Sections */
.section { padding: var(--space-section) 0; }
.section-tint { background: var(--card); border-block: 1px solid var(--line); }
.section-ink { background: var(--ink); color: #fff; }
.section-ink .eyebrow { color: var(--teal); }

/* Bento */
.bento { display: grid; grid-template-columns: repeat(6, 1fr); gap: 1.25rem; margin-top: 2.5rem; }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 1.75rem;
  transition: transform var(--duration-fast) var(--ease-out), box-shadow var(--duration-fast);
}
.bento .card { grid-column: span 2; }
.bento .card-feature { grid-column: span 3; display: flex; flex-direction: column; }
.bento .card:hover { transform: translateY(-3px); box-shadow: 0 10px 30px -12px rgba(15, 39, 71, 0.25); }
.card-feature .btn { margin-top: auto; align-self: flex-start; }
.card-ink { background: var(--ink); color: #fff; border-color: var(--ink); }
.card-ink .card-kicker, .card-ink .fine { color: #b9c4d6; }
.card-ink .ticks li::before { color: var(--teal); }
.card-kicker { font-family: var(--font-mono); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); margin-bottom: 0.75rem; }
.card h3 { font-size: 1.5rem; }
.price { font-size: 0.95rem; margin-bottom: 1.2rem; }
.price .mono { font-weight: 600; font-size: 1.05rem; }
.ticks { list-style: none; padding: 0; margin: 0 0 1.2rem; display: grid; gap: 0.6rem; }
.ticks li { padding-left: 1.6rem; position: relative; }
.ticks li::before { content: "✓"; position: absolute; left: 0; color: var(--teal-text); font-weight: 700; }
.fine { font-size: 0.85rem; color: var(--muted); }
.chips { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.chips li { font-family: var(--font-mono); font-size: 0.8rem; padding: 0.3rem 0.7rem; border: 1px solid var(--line); border-radius: 999px; background: var(--paper); }

/* Calculator */
.calc-grid { display: grid; grid-template-columns: 0.9fr 1.1fr; gap: clamp(2rem, 1rem + 4vw, 4.5rem); align-items: start; }
.calc { display: grid; gap: 1rem; box-shadow: 10px 10px 0 -1px var(--teal); }
.field { display: grid; gap: 0.35rem; }
.field label { font-size: 0.85rem; font-weight: 600; color: var(--ink-soft); }
.field input[type="text"] {
  font: 600 1.05rem/1.2 var(--font-mono); color: var(--ink);
  padding: 0.7rem 0.85rem; border: 1.5px solid var(--muted); border-radius: var(--radius-small); background: var(--paper);
  min-height: 48px; width: 100%;
  transition: border-color var(--duration-fast), background-color var(--duration-fast);
}
.field input[type="text"]:hover { border-color: var(--ink-soft); }
.field input[type="text"]:focus { border-color: var(--ink); background: #fff; outline: 2px solid transparent; box-shadow: 0 0 0 3px color-mix(in srgb, var(--teal) 40%, transparent); }
.field input[aria-invalid="true"] { border-color: var(--amber); }
.field-pair { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.field-check { display: flex; align-items: center; gap: 0.6rem; align-self: end; min-height: 48px; }
.field-check input { width: 22px; height: 22px; accent-color: var(--ink); }
.calc-out { border-top: 1px dashed var(--line); padding-top: 1rem; }
.calc-out dl { margin: 0; display: grid; gap: 0.5rem; }
.calc-out dd { font-size: 1rem; }
.calc-error { color: var(--amber); font-weight: 600; font-size: 0.9rem; }
.pace-short { color: var(--amber); }
.pace-ok { color: var(--teal-text); }

/* Approach */
.steps { list-style: none; counter-reset: step; padding: 0; margin: 2.5rem 0 0; display: grid; grid-template-columns: repeat(4, 1fr); gap: 1.25rem; }
.steps li { counter-increment: step; border-top: 3px solid var(--ink); padding-top: 1rem; }
.steps li::before { content: "0" counter(step); font-family: var(--font-mono); font-weight: 600; color: var(--teal-text); display: block; margin-bottom: 0.5rem; }
.steps p { color: var(--ink-soft); font-size: 0.95rem; }
.principles { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.25rem; margin-top: 3.5rem; padding: 2rem; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); }
.principles p { color: var(--ink-soft); font-size: 0.95rem; margin: 0; }

/* Contact */
.contact-grid { display: grid; grid-template-columns: 1.2fr 0.8fr; gap: 2rem; align-items: center; }
.section-ink h2 { max-width: 18ch; }
.section-ink p { color: #c9d2e1; }
.contact-actions { display: grid; gap: 1rem; justify-items: start; }
.contact-actions .btn { font-family: var(--font-mono); }
.text-link { color: #fff; text-underline-offset: 4px; }
.text-link:hover { color: var(--teal); }

/* Footer */
.site-footer { background: var(--navy-deep); color: #a9b5c8; font-size: 0.85rem; }
.footer-row { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 0.5rem 2rem; padding-block: 1.5rem; }
.footer-row p { margin: 0; }

/* Responsive */
@media (max-width: 960px) {
  .hero-grid, .calc-grid, .contact-grid { grid-template-columns: 1fr; }
  .ledger { transform: none; max-width: 520px; }
  .bento .card, .bento .card-feature { grid-column: span 6; }
  .steps { grid-template-columns: repeat(2, 1fr); }
  .principles { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .nav a:not(.btn) { display: none; }
  .steps { grid-template-columns: 1fr; }
  .field-pair { grid-template-columns: 1fr; }
  .ledger { box-shadow: 8px 8px 0 -1px var(--ink); }
  .calc { box-shadow: 6px 6px 0 -1px var(--teal); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; }
  .ledger { transform: none; }
}