:root {
	--bg: #f7f5ef;
	--panel: #ffffff;
	--ink: #143033;
	--muted: #596b68;
	--brand: #0f6f72;
	--brand-dark: #12343b;
	--accent: #a94126;
	--danger: #9d1f1f;
	--line: #d8ddd5;
	--soft: #e9f2ef;
	--focus: #8f3dff;
	--shadow: 0 1.25rem 3rem rgba(18, 52, 59, 0.12);
	color-scheme: light;
	font-family: Arial, Helvetica, sans-serif;
}

* {
	box-sizing: border-box;
}

html {
	scroll-behavior: smooth;
}

body {
	margin: 0;
	background: var(--bg);
	color: var(--ink);
	font-size: 1rem;
	line-height: 1.5;
}

a {
	color: var(--brand-dark);
}

a:hover {
	color: var(--accent);
}

a:focus-visible,
button:focus-visible,
input:focus-visible {
	outline: 0.2rem solid var(--focus);
	outline-offset: 0.18rem;
}

.site-header,
.site-footer,
main > section {
	padding-inline: clamp(1rem, 4vw, 4rem);
}

.site-header {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 1rem;
	padding-block: 1rem;
	background: rgba(247, 245, 239, 0.94);
	border-bottom: 0.0625rem solid var(--line);
	position: sticky;
	top: 0;
	z-index: 3;
}

.brand {
	display: inline-flex;
	align-items: center;
	gap: 0.75rem;
	text-decoration: none;
	color: var(--ink);
}

.brand-mark {
	display: grid;
	place-items: center;
	width: 2.75rem;
	aspect-ratio: 1;
	border-radius: 50%;
	background: var(--brand-dark);
	color: #ffffff;
	font-size: 1.7rem;
	font-weight: 700;
}

.brand strong,
.brand span span {
	display: block;
}

.brand span span {
	color: var(--muted);
	font-size: 0.9rem;
}

nav {
	display: flex;
	flex-wrap: wrap;
	justify-content: flex-end;
	gap: 0.75rem 1.25rem;
}

nav a {
	font-weight: 700;
	text-decoration-thickness: 0.08rem;
	text-underline-offset: 0.25rem;
}

.hero {
	display: grid;
	grid-template-columns: minmax(0, 1.15fr) minmax(17rem, 0.85fr);
	align-items: center;
	gap: clamp(1.5rem, 5vw, 4rem);
	min-height: 38rem;
	padding-block: clamp(3rem, 8vw, 6rem);
	background:
		linear-gradient(135deg, rgba(15, 111, 114, 0.08), rgba(200, 79, 49, 0.1)),
		var(--bg);
}

.hero-copy {
	max-width: 47rem;
}

.eyebrow {
	margin: 0 0 0.65rem;
	color: var(--accent);
	font-size: 0.82rem;
	font-weight: 700;
	letter-spacing: 0;
	text-transform: uppercase;
}

h1,
h2 {
	margin: 0;
	line-height: 1.08;
	letter-spacing: 0;
}

h1 {
	font-size: clamp(2.5rem, 7vw, 5.7rem);
	max-width: 12ch;
}

h2 {
	font-size: clamp(1.8rem, 4vw, 3rem);
}

.hero-copy p:last-child,
.section-heading p:last-child {
	max-width: 48rem;
	color: var(--muted);
	font-size: 1.12rem;
}

.equation-panel {
	display: grid;
	align-items: center;
	gap: 1rem;
	min-height: 18rem;
	margin: 0;
	padding: clamp(1.25rem, 4vw, 2.25rem);
	border: 0.0625rem solid var(--line);
	border-radius: 0.5rem;
	background: var(--panel);
	box-shadow: var(--shadow);
	color: var(--brand-dark);
	font-size: clamp(3rem, 9vw, 6rem);
	font-weight: 800;
	text-align: center;
}

.equation-panel img {
	display: block;
	width: 100%;
	height: auto;
}

.equation-panel figcaption {
	display: grid;
	grid-template-columns: 1fr auto 1fr 1fr;
	align-items: center;
	gap: clamp(0.45rem, 2vw, 1rem);
}

.equation-panel figcaption span:nth-child(4) {
	color: var(--accent);
}

.calculator-section,
.formulae-section,
.units-section {
	padding-block: clamp(2.5rem, 6vw, 4.5rem);
}

.section-heading {
	margin-bottom: 1.5rem;
}

.calculator {
	display: grid;
	gap: 1rem;
}

fieldset {
	margin: 0;
	padding: clamp(1rem, 3vw, 1.5rem);
	border: 0.0625rem solid var(--line);
	border-radius: 0.5rem;
	background: var(--panel);
	box-shadow: 0 0.6rem 1.5rem rgba(18, 52, 59, 0.06);
}

legend {
	padding-inline: 0.35rem;
	font-size: 1.15rem;
	font-weight: 700;
}

.field-grid {
	display: grid;
	grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
	gap: 1rem;
	margin-top: 1rem;
}

.field {
	display: grid;
	gap: 0.45rem;
	align-content: start;
	min-width: 0;
	font-weight: 700;
}

.field.is-conflicted .input-row {
	border-color: var(--danger);
	box-shadow: 0 0 0 0.12rem rgba(157, 31, 31, 0.18);
}

.field.is-conflicted .field-note {
	color: var(--danger);
}

.input-row {
	display: grid;
	grid-template-columns: minmax(0, 1fr) auto;
	align-items: stretch;
	border: 0.0625rem solid #aebbb6;
	border-radius: 0.5rem;
	background: #ffffff;
	overflow: hidden;
}

input {
	width: 100%;
	min-height: 3rem;
	border: 0;
	padding: 0.7rem 0.85rem;
	color: var(--ink);
	font: inherit;
	font-size: 1.05rem;
}

.field.is-calculated input {
	background: var(--soft);
}

.unit {
	display: inline-flex;
	align-items: center;
	justify-content: center;
	min-width: 4.5rem;
	padding-inline: 0.75rem;
	border-left: 0.0625rem solid var(--line);
	background: #edf3f0;
	color: var(--brand-dark);
	font-weight: 700;
	white-space: nowrap;
}

.field-note {
	min-height: 1.3rem;
	color: var(--muted);
	font-size: 0.88rem;
	font-weight: 400;
}

.field.is-calculated .field-note::after {
	content: " - calculated";
	color: var(--brand);
	font-weight: 700;
}

.recalculate {
	justify-self: start;
	min-height: 2.35rem;
	padding: 0.45rem 0.7rem;
	background: #f6e4de;
	color: var(--danger);
	font-size: 0.9rem;
}

.recalculate:hover {
	background: #edd0c6;
	color: #731515;
}

.actions {
	display: flex;
	align-items: center;
	justify-content: space-between;
	gap: 1rem;
	flex-wrap: wrap;
	padding: 1rem 0 0;
}

button {
	min-height: 2.85rem;
	border: 0;
	border-radius: 0.5rem;
	padding: 0.75rem 1rem;
	background: var(--brand-dark);
	color: #ffffff;
	cursor: pointer;
	font: inherit;
	font-weight: 700;
}

button:hover {
	background: var(--brand);
}

.status {
	margin: 0;
	color: var(--muted);
	font-weight: 700;
}

.formula-list {
	display: grid;
	grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
	gap: 1rem;
	margin: 0;
	padding: 0;
	list-style: none;
}

.formula-list li {
	display: grid;
	gap: 0.35rem;
	padding: 1.1rem;
	border: 0.0625rem solid var(--line);
	border-radius: 0.5rem;
	background: var(--panel);
}

.formula-list strong {
	color: var(--brand-dark);
	font-size: 1.35rem;
}

.formula-list span {
	color: var(--muted);
}

.unit-list {
	display: grid;
	grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
	gap: 1rem;
	margin: 0;
	padding: 0;
}

.unit-list div {
	display: grid;
	grid-template-columns: auto minmax(0, 1fr);
	gap: 1rem;
	align-items: center;
	min-height: 6.25rem;
	padding: 1rem 1.1rem;
	border: 0.0625rem solid var(--line);
	border-radius: 0.5rem;
	background:
		linear-gradient(90deg, rgba(15, 111, 114, 0.08), rgba(15, 111, 114, 0) 38%),
		var(--panel);
	box-shadow: 0 0.45rem 1.1rem rgba(18, 52, 59, 0.06);
}

.unit-list dt {
	display: inline-grid;
	place-items: center;
	width: 3.7rem;
	aspect-ratio: 1;
	border: 0.0625rem solid rgba(18, 52, 59, 0.18);
	border-radius: 0.5rem;
	background: #eef5f2;
	color: var(--brand-dark);
	font-size: 1.3rem;
	font-weight: 800;
	line-height: 1;
}

.unit-list dd {
	margin: 0;
	color: var(--muted);
	font-size: 0.96rem;
}

.site-footer {
	padding-block: 1.5rem;
	border-top: 0.0625rem solid var(--line);
	color: var(--muted);
	text-align: center;
}

.site-footer p {
	margin: 0;
}

@media (max-width: 48rem) {
	.site-header {
		align-items: flex-start;
		flex-direction: column;
		position: static;
	}

	nav {
		justify-content: flex-start;
	}

	.hero {
		grid-template-columns: 1fr;
		min-height: auto;
	}

	h1 {
		max-width: none;
	}

	.equation-panel {
		min-height: 12rem;
	}

	.unit-list {
		grid-template-columns: 1fr;
	}

	.unit-list div {
		align-items: start;
	}
}

@media (prefers-reduced-motion: reduce) {
	html {
		scroll-behavior: auto;
	}
}