/* ==========================================================================
   BioRevit Clinic — design language ported from Human Longevity
   (clean, airy, large type, numbered rhythm, generous white space)
   + Superpower's scroll-driven screen swap on the "how it works" section.

   Palette lives in :root so a redesign is a one-block edit.
   ========================================================================== */

:root {
	--ivory: #ffffff;
	--paper: #ffffff;
	--wash: #f4f4f2;          /* media / placeholder blocks */
	--ink: #0e1114;
	--ink-soft: #626a72;
	--ink-faint: #9aa2a9;
	--line: #e6e6e3;
	--accent: #1f6f63;
	--accent-soft: #eef5f3;

	--shell: 1220px;
	--gap: clamp(1.25rem, 4vw, 3.5rem);
	--radius: 4px;

	--step--1: clamp(0.78rem, 0.76rem + 0.1vw, 0.84rem);
	--step-0:  clamp(1rem, 0.96rem + 0.2vw, 1.09rem);
	--step-1:  clamp(1.15rem, 1.05rem + 0.5vw, 1.45rem);
	--step-2:  clamp(1.7rem, 1.35rem + 1.7vw, 3rem);
	--step-3:  clamp(2.4rem, 1.6rem + 3.6vw, 5rem);

	--ease: cubic-bezier(0.22, 0.61, 0.36, 1);

	/* Type system — ported from humanlongevity.com.
	   Sans for everything, a serif italic for the single accent word in a heading,
	   mono for the tiny uppercase labels. */
	--font-sans: "Bai Jamjuree", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
	--font-accent: "Instrument Serif", ui-serif, Georgia, "Times New Roman", serif;
	--font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

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

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

body {
	margin: 0;
	background: var(--ivory);
	color: var(--ink);
	font-family: var(--font-sans);
	font-size: var(--step-0);
	line-height: 1.6;
	-webkit-font-smoothing: antialiased;
	text-rendering: optimizeLegibility;
}

img { max-width: 100%; height: auto; display: block; }
a { color: inherit; text-decoration: none; }
a:hover { text-decoration: none; }
button { font: inherit; }

h1, h2, h3, h4 { margin: 0 0 0.45em; letter-spacing: -0.033em; line-height: 1.06; font-weight: 500; }
h1 { font-size: var(--step-3); }
h2 { font-size: var(--step-2); }
h3 { font-size: var(--step-1); letter-spacing: -0.02em; }
p  { margin: 0 0 1em; }
p:last-child { margin-bottom: 0; }

/* the italic emphasis word inside headings — Human Longevity's signature:
   a SERIF italic set inside a sans heading, slightly larger so it optically
   matches the x-height of the surrounding sans. */
em.acc {
	font-family: var(--font-accent);
	font-style: italic;
	font-weight: 400;
	letter-spacing: -0.01em;
	font-size: 1.06em;
}

.shell { width: min(100% - 2 * var(--gap), var(--shell)); margin-inline: auto; }

section { padding-block: clamp(3.5rem, 9vw, 8rem); }
.rule { border-top: 1px solid var(--line); }

.eyebrow {
	font-family: var(--font-mono);
	font-size: var(--step--1);
	letter-spacing: 0.16em;
	text-transform: uppercase;
	color: var(--ink-faint);
	font-weight: 400;
	margin: 0 0 1.4rem;
}

.lede { font-size: var(--step-1); color: var(--ink-soft); max-width: 56ch; letter-spacing: -0.01em; }

/* --- header --------------------------------------------------------------- */

.site-head {
	position: sticky; top: 0; z-index: 60;
	background: color-mix(in srgb, #fff 86%, transparent);
	backdrop-filter: saturate(180%) blur(12px);
	border-bottom: 1px solid transparent;
	transition: border-color 0.3s var(--ease);
}
.site-head.is-stuck { border-bottom-color: var(--line); }

.site-head .shell { display: flex; align-items: center; gap: 2rem; min-height: 72px; }

.brand { font-weight: 600; letter-spacing: 0.02em; font-size: 0.98rem; display: flex; align-items: baseline; gap: 0.5ch; }
.brand b { font-weight: 700; letter-spacing: 0.08em; }
.brand span { color: var(--ink-faint); font-weight: 400; letter-spacing: 0.02em; }

.site-head nav { margin-inline-start: auto; }
.site-head nav ul {
	display: flex; gap: 1.75rem; margin: 0; padding: 0; list-style: none;
	font-size: 0.92rem; color: var(--ink-soft);
}
.site-head nav a { transition: color 0.2s var(--ease); }
.site-head nav a:hover { color: var(--ink); }

/* --- buttons -------------------------------------------------------------- */

.btn {
	display: inline-flex; align-items: center; gap: 0.6ch;
	padding: 0.72rem 1.4rem; border-radius: 2px;
	font-size: 0.92rem; font-weight: 500; letter-spacing: -0.005em;
	border: 1px solid var(--ink); background: var(--ink); color: #fff;
	transition: opacity 0.25s var(--ease);
}
.btn:hover { opacity: 0.86; }
.btn--ghost { background: transparent; color: var(--ink); border-color: var(--line); }
.btn--ghost:hover { border-color: var(--ink); opacity: 1; }
.btn--sm { padding: 0.55rem 1.05rem; font-size: 0.86rem; }

.cta-row { display: flex; gap: 0.7rem; flex-wrap: wrap; align-items: center; }

/* --- hero ----------------------------------------------------------------- */

.hero { padding-block: clamp(3rem, 7vw, 6rem) clamp(2rem, 5vw, 4rem); }
.hero h1 { max-width: 17ch; margin-bottom: 0.55em; }
.hero .lede { max-width: 52ch; }
.hero .cta-row { margin-top: 2.2rem; }

.hero__lead {
	font-size: var(--step-1);
	line-height: 1.5;
	color: var(--ink);
	max-width: 48ch;
	margin-bottom: 0.8em;
}
.hero__lead strong { font-weight: 600; }
.hero__lead--close {
	color: var(--ink-soft);
	font-size: var(--step-0);
	margin-bottom: 0;
}

/* --- numbered feature cards ---------------------------------------------- */

.head-row { display: flex; flex-wrap: wrap; gap: 1.5rem 3rem; align-items: flex-end; justify-content: space-between; margin-bottom: clamp(2rem, 4vw, 3.5rem); }
.head-row h2 { max-width: 22ch; margin-bottom: 0; }
.head-row p { max-width: 40ch; color: var(--ink-soft); margin-bottom: 0.4rem; }

.num-grid { display: grid; gap: 1.5rem; grid-template-columns: repeat(auto-fit, minmax(230px, 1fr)); }

.num-card { border-top: 1px solid var(--ink); padding-top: 1.1rem; }
.num-card__n { font-family: var(--font-mono); font-size: var(--step--1); letter-spacing: 0.14em; color: var(--ink-faint); }
.num-card__media { background: var(--wash); border-radius: var(--radius); aspect-ratio: 4 / 3; margin: 1rem 0 1.1rem; }
.num-card h3 { font-size: 1.12rem; margin-bottom: 0.35em; }
.num-card p { color: var(--ink-soft); font-size: 0.94rem; }

/* --- split ---------------------------------------------------------------- */

.split { display: grid; gap: var(--gap); grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); align-items: center; }
.split__media {
	background: var(--wash); border-radius: var(--radius);
	aspect-ratio: 5 / 4; display: grid; place-items: center;
	color: var(--ink-faint); font-size: var(--step--1);
	letter-spacing: 0.16em; text-transform: uppercase;
}

/* --- proof screenshot ----------------------------------------------------- */

.proof__media {
	aspect-ratio: 16 / 10;
	background: #1a1d20;
	border-radius: var(--radius);
	display: grid; place-items: center;
	color: rgba(255,255,255,0.4);
	font-size: var(--step--1);
	letter-spacing: 0.16em; text-transform: uppercase;
}

/* --- contact -------------------------------------------------------------- */

.contact__grid { display: grid; gap: 2rem; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); margin-top: 2.5rem; }
.contact__grid h4 { font-family: var(--font-mono); font-size: var(--step--1); letter-spacing: 0.14em; text-transform: uppercase; color: var(--ink-faint); font-weight: 400; margin-bottom: 0.7em; }
.contact__grid p { color: var(--ink-soft); font-size: 0.96rem; }
.contact__grid a { border-bottom: 1px solid var(--line); }
.contact__grid a:hover { border-bottom-color: var(--ink); }

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

.site-foot { border-top: 1px solid var(--line); padding-block: 3rem; color: var(--ink-faint); font-size: 0.88rem; }
.site-foot .shell { display: flex; flex-wrap: wrap; gap: 1rem 2rem; justify-content: space-between; }

/* --- responsive ----------------------------------------------------------- */

@media (max-width: 820px) {
	.site-head nav { display: none; }
	.hero h1 { max-width: none; }
}

/* --- a11y ----------------------------------------------------------------- */

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