:root {
  --bg: #f3f0e8;
  --ink: #16181c;
  --muted: #4b5560;
  --line: #c9cfd6;
  --paper: #fcfbf8;
  --result: #e7f2e8;
  --cta: #c45c0a;
  --cta-ink: #fff;
  --focus: #1d4e89;
  --max: 40rem;
  --tap: 2.85rem;
}

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

html {
  font-size: 112.5%;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: system-ui, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.45;
}

img,
svg {
  max-width: 100%;
}

a {
  color: var(--focus);
}

a:focus-visible,
button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 2px;
}

.wrap {
  width: min(var(--max), calc(100% - 1.5rem));
  margin-inline: auto;
}

.site-header {
  padding: 0.85rem 0 0.5rem;
  border-bottom: 1px solid var(--line);
  background: var(--paper);
}

.brand {
  font-weight: 750;
  letter-spacing: -0.03em;
  text-decoration: none;
  color: var(--ink);
  font-size: 1.15rem;
}

.brand span {
  color: var(--cta);
}

.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 0.9rem;
  margin-top: 0.45rem;
  font-size: 0.92rem;
}

.nav a {
  color: var(--muted);
  text-decoration: none;
  min-height: var(--tap);
  display: inline-flex;
  align-items: center;
}

.nav a[aria-current="page"] {
  color: var(--ink);
  font-weight: 650;
}

main {
  padding: 1.25rem 0 3rem;
}

h1 {
  font-size: 1.65rem;
  letter-spacing: -0.03em;
  line-height: 1.2;
  margin: 0 0 0.4rem;
}

.lede {
  margin: 0 0 1rem;
  color: var(--muted);
}

.unit-bar {
  display: flex;
  gap: 0.35rem;
  margin: 0 0 1rem;
}

.unit-bar button {
  min-height: var(--tap);
  min-width: var(--tap);
  padding: 0 0.85rem;
  border: 1px solid var(--line);
  background: var(--paper);
  color: var(--ink);
  border-radius: 0.4rem;
  font: inherit;
  font-weight: 650;
  cursor: pointer;
}

.unit-bar button[aria-pressed="true"] {
  background: var(--ink);
  color: #fff;
  border-color: var(--ink);
}

.card {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 0.7rem;
  padding: 1rem;
}

label {
  display: block;
  font-weight: 650;
  margin: 0.65rem 0 0.3rem;
}

.field {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 0.4rem;
  align-items: center;
}

input,
select {
  width: 100%;
  min-height: var(--tap);
  border: 1px solid #8b939c;
  border-radius: 0.4rem;
  padding: 0.4rem 0.65rem;
  font: inherit;
  font-variant-numeric: tabular-nums;
  background: #fff;
  color: var(--ink);
}

.unit {
  color: var(--muted);
  font-weight: 650;
  min-width: 2.2rem;
}

.result {
  margin-top: 1rem;
  background: var(--result);
  border: 1px solid #b7d0ba;
  border-radius: 0.7rem;
  padding: 1rem 1rem 1.1rem;
}

.example {
  font-size: 0.9rem;
  color: var(--muted);
  margin: 0 0 0.4rem;
}

.big {
  font-size: clamp(2.1rem, 8vw, 3.1rem);
  font-weight: 800;
  letter-spacing: -0.04em;
  font-variant-numeric: tabular-nums;
  line-height: 1.05;
  margin: 0;
}

.sub,
.pad,
.order {
  margin: 0.35rem 0 0;
  font-variant-numeric: tabular-nums;
}

.order {
  font-weight: 750;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.75rem;
}

.btn {
  min-height: var(--tap);
  padding: 0.45rem 1rem;
  border-radius: 0.45rem;
  border: 1px solid var(--line);
  background: var(--paper);
  color: var(--ink);
  font: inherit;
  font-weight: 650;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}

.btn-cta {
  background: var(--cta);
  border-color: var(--cta);
  color: var(--cta-ink);
  width: 100%;
  font-size: 1.05rem;
}

.btn-ghost {
  background: transparent;
}

.commerce {
  margin-top: 1.1rem;
}

.commerce p {
  margin: 0.4rem 0 0.7rem;
  color: var(--muted);
}

.quiet {
  font-size: 0.92rem;
  color: var(--muted);
}

.tools {
  display: grid;
  gap: 0.65rem;
  margin: 1rem 0;
}

.tools a {
  display: block;
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 0.65rem;
  padding: 0.9rem 1rem;
  text-decoration: none;
  color: var(--ink);
  min-height: var(--tap);
}

.tools a strong {
  display: block;
  font-size: 1.05rem;
}

.tools a span {
  color: var(--muted);
  font-size: 0.92rem;
}

.prose h2 {
  font-size: 1.15rem;
  margin: 1.4rem 0 0.4rem;
}

.prose p,
.prose li {
  color: var(--ink);
}

.prose ul {
  padding-left: 1.15rem;
}

.faq details {
  border-top: 1px solid var(--line);
  padding: 0.55rem 0;
}

.faq summary {
  cursor: pointer;
  font-weight: 650;
  min-height: var(--tap);
  display: flex;
  align-items: center;
}

.math {
  margin-top: 0.8rem;
  font-size: 0.92rem;
  color: var(--muted);
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 1.2rem 0 2rem;
  font-size: 0.88rem;
  color: var(--muted);
}

.site-footer nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1rem;
  margin-bottom: 0.5rem;
}

.site-footer a {
  color: var(--muted);
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
}

.sketch {
  width: 100%;
  height: auto;
  margin: 0.6rem 0 1rem;
}

.ad-slot {
  min-height: 0;
  margin-top: 1.25rem;
  /* Manual AdSense unit goes here later — never between calc fields. */
}