:root {
  --frost: #eef2f3;
  --white: #ffffff;
  --ink: #13212a;
  --steel: #4a5b64;
  --rule: #c9d3d7;
  --cold: #2f6fd6;
  --warm: #e98a15;
  --wrap: 1120px;
  --display: "Anybody", "Arial Black", sans-serif;
  --body: "Atkinson Hyperlegible Next", system-ui, sans-serif;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--frost); color: var(--ink); font: 400 1.0625rem/1.6 var(--body); }
h1, h2, h3 { font-family: var(--display); margin: 0; }
h2 { font-size: clamp(1.75rem, 3.6vw, 2.5rem); font-weight: 800; font-stretch: 125%; line-height: 1.05; letter-spacing: -.01em; margin-bottom: .6em; }
h3 { font-size: 1.15rem; font-weight: 700; font-stretch: 110%; line-height: 1.2; margin-bottom: .4em; }
p { margin: 0 0 1em; max-width: 66ch; }
a { color: inherit; }
:focus-visible { outline: 3px solid var(--cold); outline-offset: 3px; }
.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 16px; }

/* header */
.top { border-bottom: 1px solid var(--rule); background: var(--frost); }
.top-in { display: flex; align-items: center; justify-content: space-between; height: 68px; gap: 16px; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; font: 900 1.3rem/1 var(--display); font-stretch: 140%; }
.brand svg { width: 30px; height: 30px; fill: none; stroke-width: 3.2; stroke-linecap: round; stroke-linejoin: round; }
.brand .bc { stroke: var(--cold); }
.brand .bw { stroke: var(--warm); }
.nav { display: flex; align-items: center; gap: 28px; font-weight: 600; font-size: .95rem; }
.nav a:not(.btn) { text-decoration: none; }
.nav a:not(.btn):hover { text-decoration: underline; text-underline-offset: 4px; }

.btn { display: inline-block; background: var(--ink); color: var(--white); font-weight: 600; text-decoration: none; padding: 13px 22px; border-radius: 6px; }
.btn:hover { background: #22394a; }
.btn-sm { padding: 8px 14px; font-size: .9rem; }
.btn-lg { padding: 16px 28px; font-size: 1.05rem; }

/* hero */
.hero { padding-top: 48px; padding-bottom: 72px; }
h1 { font-size: clamp(2.2rem, 5vw, 4.2rem); font-weight: 900; font-stretch: 140%; line-height: .98; letter-spacing: -.02em; max-width: 17ch; }
.lede { font-size: 1.15rem; color: var(--steel); margin-top: 20px; max-width: 64ch; }

.rig {
  margin-top: 32px; background: var(--white); border: 1px solid var(--rule); border-radius: 14px; padding: 28px;
  display: grid; grid-template-columns: 170px 1fr 170px; grid-template-areas: "in svg stale" "exh svg sup" "dial dial dial";
  column-gap: 12px; row-gap: 8px; align-items: center;
}
.core-svg { grid-area: svg; width: 100%; height: auto; display: block; }
.r-in { grid-area: in; --c: var(--t-in); }
.r-stale { grid-area: stale; --c: var(--t-room); text-align: right; }
.r-exh { grid-area: exh; --c: var(--t-exh); }
.r-sup { grid-area: sup; --c: var(--t-sup); text-align: right; }
.read span { display: block; font-size: .85rem; color: var(--steel); line-height: 1.3; }
.read b { display: block; font: 800 clamp(2.4rem, 5vw, 3.6rem)/1 var(--display); font-stretch: 120%; color: var(--c, var(--ink)); font-variant-numeric: tabular-nums; margin-top: 4px; transition: color .2s; }
.r-sup b { font-size: clamp(3rem, 6.5vw, 4.6rem); }

.duct { fill: none; stroke: var(--frost); stroke-width: 34; stroke-linejoin: round; }
.flow { fill: none; stroke-width: 8; stroke-linecap: round; stroke-linejoin: round; stroke-dasharray: 16 12; animation: flow 1.4s linear infinite; transition: stroke .2s; }
@keyframes flow { to { stroke-dashoffset: -28; } }
.core-box { fill: var(--white); stroke: var(--ink); stroke-width: 3; }
.plate { stroke: var(--steel); stroke-width: 2; }
.core-lbl { font: 600 20px var(--body); fill: var(--steel); }

.dial { grid-area: dial; border-top: 1px solid var(--rule); margin-top: 16px; padding-top: 20px; }
.dial label { display: flex; justify-content: space-between; align-items: baseline; font-weight: 600; }
.dial output { font: 800 1.4rem var(--display); font-stretch: 120%; font-variant-numeric: tabular-nums; color: var(--t-in); }
input[type=range] { width: 100%; margin: 14px 0 12px; appearance: none; -webkit-appearance: none; height: 10px; border-radius: 5px; background: linear-gradient(90deg, var(--cold), #7d8b93 73%, var(--warm)); }
input[type=range]::-webkit-slider-thumb { -webkit-appearance: none; width: 30px; height: 30px; border-radius: 50%; background: var(--white); border: 3px solid var(--ink); cursor: grab; }
input[type=range]::-moz-range-thumb { width: 26px; height: 26px; border-radius: 50%; background: var(--white); border: 3px solid var(--ink); cursor: grab; }
.verdict { font-size: 1.1rem; margin: 0; min-height: 3.2em; }
.fine { font-size: .85rem; color: var(--steel); margin-top: 12px; }

/* why */
.why { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; padding-top: 88px; padding-bottom: 88px; border-top: 1px solid var(--rule); }
.why-text p { color: var(--steel); }
.problems { margin: 0; }
.problems div { padding: 18px 0; border-bottom: 1px solid var(--rule); }
.problems div:first-child { padding-top: 6px; }
.problems dt { font: 700 1.1rem var(--display); font-stretch: 110%; }
.problems dd { margin: 4px 0 0; color: var(--steel); }

/* how: a real sequence, so it keeps its numbers */
.how { background: var(--ink); color: var(--frost); padding: 88px 0; }
.steps { list-style: none; margin: 40px 0 0; padding: 0; display: grid; grid-template-columns: repeat(3, 1fr); gap: 32px; counter-reset: s; position: relative; }
.steps::before { content: ""; position: absolute; left: 0; right: 0; top: 23px; height: 4px; background: linear-gradient(90deg, #7d8b93, var(--cold) 45%, var(--cold)); border-radius: 2px; }
.steps li { counter-increment: s; position: relative; }
.steps li::before { content: counter(s); display: grid; place-items: center; width: 50px; height: 50px; border-radius: 50%; background: var(--ink); border: 3px solid var(--frost); font: 800 1.2rem var(--display); margin-bottom: 20px; position: relative; }
.steps p { color: #b7c4ca; }

/* compare */
.compare { padding-top: 88px; padding-bottom: 24px; }
.compare > p { color: var(--steel); }
.table-scroll { overflow-x: auto; margin-top: 24px; }
table { border-collapse: collapse; width: 100%; background: var(--white); border: 1px solid var(--rule); border-radius: 10px; overflow: hidden; }
th, td { text-align: left; padding: 14px 18px; border-bottom: 1px solid var(--rule); vertical-align: top; }
thead th { font: 800 1.2rem var(--display); font-stretch: 125%; background: var(--frost); }
tbody th { font-weight: 600; width: 26%; }
tbody tr:last-child > * { border-bottom: 0; }

/* faq */
.faq { padding-top: 88px; padding-bottom: 88px; max-width: 880px; margin-left: max(0px, calc((100% - var(--wrap)) / 2)); }
details { border-bottom: 1px solid var(--rule); }
details:first-of-type { border-top: 1px solid var(--rule); }
summary { cursor: pointer; font: 700 1.15rem var(--display); font-stretch: 110%; padding: 20px 0; list-style: none; display: flex; justify-content: space-between; gap: 16px; }
summary::-webkit-details-marker { display: none; }
summary::after { content: "+"; font-size: 1.5rem; line-height: 1; color: var(--cold); }
details[open] summary::after { content: "–"; }
details p { color: var(--steel); margin-bottom: 20px; }

/* contact */
.contact { background: var(--white); border-top: 1px solid var(--rule); padding: 88px 0; }
.contact p { color: var(--steel); }
.contact .btn { margin-top: 8px; }

.foot { border-top: 1px solid var(--rule); padding: 24px 0; font-size: .9rem; color: var(--steel); }
.foot-in { display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; }

@media (prefers-reduced-motion: reduce) {
  .flow { animation: none; stroke-dasharray: none; }
  html { scroll-behavior: auto; }
}
@media (max-width: 860px) {
  .nav a:not(.btn) { display: none; }
  .hero { padding-top: 40px; }
  .rig { padding: 18px; grid-template-columns: 1fr 1fr; grid-template-areas: "in stale" "svg svg" "exh sup" "dial dial"; row-gap: 12px; }
  .why { grid-template-columns: 1fr; gap: 24px; }
  .steps { grid-template-columns: 1fr; }
  .steps::before { left: 23px; right: auto; top: 0; bottom: 0; width: 4px; height: auto; background: linear-gradient(180deg, #7d8b93, var(--cold) 45%, var(--cold)); }
  .steps li { padding-left: 72px; }
  .steps li::before { position: absolute; left: 0; top: -6px; margin: 0; }
  th, td { padding: 12px 10px; font-size: .95rem; }
  tbody th { width: 34%; }
}