/* RENA — Knee Rehabilitation Exoskeleton
   Editorial research site. Light mode. Warm cream paper.
   ------------------------------------------------------ */

:root {
  --bg:           #fafaf7;
  --bg-warm:      #f4f2eb;
  --bg-cool:      #f0eee5;
  --bg-edge:      #e6e4db;
  --ink:          #1a1a17;
  --ink-muted:    #6b6b63;
  --ink-faint:    #9c9a91;
  --rule:         #d8d6cf;
  --rule-strong:  #c3c0b6;
  --accent:       #3d7a5a;
  --accent-soft:  #d6e3da;
  --accent-faint: #ecf1ed;
  --series-grey:  #8a8478;
  --series-clay:  #a87156;

  --serif: "Fraunces", "Source Serif Pro", Georgia, serif;
  --sans:  "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --mono:  "JetBrains Mono", "SF Mono", ui-monospace, Menlo, monospace;

  --maxw: 1180px;
  --gutter: clamp(20px, 4vw, 56px);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body { position: relative; overflow-x: hidden; }

/* Paper grain overlay — SVG turbulence */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 100;
  background-image: url("paper-grain.svg");
  background-size: 240px 240px;
  opacity: 0.045;
  mix-blend-mode: multiply;
}

/* Selection */
::selection { background: var(--accent); color: var(--bg); }

/* Type ---------------------------------------------------- */

h1, h2, h3, h4 {
  font-family: var(--serif);
  font-weight: 400;
  color: var(--ink);
  letter-spacing: -0.02em;
  margin: 0;
  text-wrap: balance;
}

h1 {
  font-size: clamp(48px, 7.4vw, 96px);
  line-height: 0.96;
  letter-spacing: -0.035em;
  font-weight: 350;
}
h2 {
  font-size: clamp(34px, 4.5vw, 56px);
  line-height: 1.05;
  letter-spacing: -0.028em;
  font-weight: 350;
}
h3 {
  font-size: clamp(22px, 2vw, 28px);
  line-height: 1.18;
  letter-spacing: -0.018em;
  font-weight: 400;
}

p { margin: 0; text-wrap: pretty; }

em, .italic { font-style: italic; }
.accent { color: var(--accent); }
.muted  { color: var(--ink-muted); }
.faint  { color: var(--ink-faint); }

.serif { font-family: var(--serif); }
.sans  { font-family: var(--sans); }
.mono  { font-family: var(--mono); }

.eyebrow {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
}
.label {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 500;
}
.section-label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--ink-muted);
}
.section-label .section-no {
  color: var(--accent);
  margin-right: 6px;
  font-variant-numeric: tabular-nums;
}

a {
  color: var(--ink);
  text-decoration: none;
  border-bottom: 1px solid var(--rule);
  transition: border-color 0.2s ease, color 0.2s ease;
}
a:hover { color: var(--accent); border-bottom-color: var(--accent); }

a.plain { border: none; }
a.plain:hover { color: var(--accent); }

/* Layout primitives -------------------------------------- */

.container {
  max-width: var(--maxw);
  margin: 0 auto;
  padding-inline: var(--gutter);
}

.container-wide {
  max-width: 1320px;
  margin: 0 auto;
  padding-inline: var(--gutter);
}

.rule { border-top: 1px solid var(--rule); height: 0; }
.rule-strong { border-top: 1px solid var(--rule-strong); height: 0; }

/* Top nav ------------------------------------------------ */

.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 50;
  background: rgba(250, 250, 247, 0.78);
  backdrop-filter: saturate(140%) blur(18px);
  -webkit-backdrop-filter: saturate(140%) blur(18px);
  border-bottom: 1px solid var(--rule);
}
.nav-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px var(--gutter);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 32px;
}
.wordmark {
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 400;
  letter-spacing: -0.01em;
  color: var(--ink);
  border: none;
  display: flex;
  align-items: baseline;
  gap: 9px;
}
.wordmark .wm-mark {
  display: inline-block;
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--accent);
  transform: translateY(-1px);
}
.wordmark .wm-em { font-style: italic; }
.nav-meta {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}
.nav-links a {
  border: none;
  color: var(--ink-muted);
  transition: color 0.2s ease;
}
.nav-links a:hover, .nav-links a.active { color: var(--accent); }
.nav-links a.cta {
  color: var(--ink);
  padding: 6px 12px;
  border: 1px solid var(--rule-strong);
  border-radius: 999px;
  display: inline-flex; align-items: center; gap: 6px;
}
.nav-links a.cta:hover {
  color: var(--accent);
  border-color: var(--accent);
}
.nav-links a.cta::after { content: "→"; font-family: var(--sans); letter-spacing: 0; }

/* Pills / chips ------------------------------------------ */

.pill {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  padding: 5px 11px;
  border: 1px solid var(--accent);
  background: var(--bg);
  color: var(--accent);
  border-radius: 999px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  font-weight: 500;
  line-height: 1.4;
  white-space: nowrap;
}
.pill .pill-num {
  font-family: var(--serif);
  font-style: italic;
  font-size: 13px;
  font-weight: 400;
}
.pill.neutral {
  border-color: var(--rule-strong);
  color: var(--ink);
}

.tag {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
}

/* Stat tiles --------------------------------------------- */

.stat {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.stat-num {
  font-family: var(--serif);
  font-weight: 350;
  font-size: clamp(38px, 4.2vw, 58px);
  line-height: 1;
  letter-spacing: -0.035em;
  color: var(--ink);
  font-variant-numeric: tabular-nums;
}
.stat-num .unit {
  font-family: var(--mono);
  font-size: 0.32em;
  font-weight: 500;
  letter-spacing: 0.05em;
  color: var(--ink-muted);
  margin-left: 6px;
  vertical-align: 0.55em;
  text-transform: uppercase;
}
.stat-num .em {
  font-style: italic;
  color: var(--accent);
}
.stat-label {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
}
.stat-sub {
  font-size: 13.5px;
  color: var(--ink-muted);
  line-height: 1.35;
  margin-top: 2px;
}

/* Buttons / CTA ------------------------------------------ */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 13px 22px;
  background: var(--accent);
  color: var(--bg);
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  border: 1px solid var(--accent);
  border-radius: 999px;
  transition: background 0.2s ease;
}
.btn:hover { background: #2f6347; border-color: #2f6347; color: var(--bg); }
.btn.ghost {
  background: transparent;
  color: var(--accent);
}
.btn.ghost:hover { background: var(--accent); color: var(--bg); }
.btn .arrow { font-family: var(--sans); font-size: 14px; letter-spacing: 0; }

/* Code blocks -------------------------------------------- */

pre.code, .code-block {
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.7;
  padding: 22px 26px;
  background: var(--bg-warm);
  border: 1px solid var(--rule);
  border-radius: 4px;
  overflow-x: auto;
  color: var(--ink);
}
.code-block .k  { color: var(--accent); }
.code-block .s  { color: var(--series-grey); }
.code-block .n  { color: #5b8a86; }       /* muted teal */
.code-block .c  { color: var(--ink-faint); font-style: italic; }
.code-block .p  { color: var(--ink-muted); }

/* Tables ------------------------------------------------- */

table.data {
  width: 100%;
  border-collapse: collapse;
  font-size: 13.5px;
  font-family: var(--sans);
}
table.data th, table.data td {
  text-align: left;
  padding: 12px 16px 12px 0;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
}
table.data th {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 500;
  border-bottom: 1px solid var(--rule-strong);
  padding-top: 0;
}
table.data td.num {
  font-family: var(--mono);
  font-variant-numeric: tabular-nums;
}
table.data tr:last-child td { border-bottom: none; }
table.data tr.total td {
  border-top: 1px solid var(--rule-strong);
  font-weight: 500;
}

/* Callout ------------------------------------------------ */

.callout {
  border-left: 2px solid var(--accent);
  padding: 4px 0 4px 22px;
  margin: 28px 0;
  font-family: var(--serif);
  font-style: italic;
  font-size: 19px;
  line-height: 1.5;
  color: var(--ink);
}
.callout .callout-tag {
  display: block;
  font-family: var(--mono);
  font-style: normal;
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 8px;
}

/* Reveal animation ---------------------------------------
   Only activates when <html> has .js-fade — set by JS only
   when the page is actually visible. Otherwise content shows
   immediately (works without JS, works in hidden iframes). */

.js-fade .reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}
.js-fade .reveal.in {
  opacity: 1;
  transform: translateY(0);
}

/* Footer ------------------------------------------------- */

footer.foot {
  border-top: 1px solid var(--rule);
  padding: 56px 0 80px;
  margin-top: 120px;
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.1em;
  color: var(--ink-muted);
}
footer.foot .container {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 24px;
  align-items: end;
}
footer.foot .colophon {
  font-family: var(--serif);
  font-style: italic;
  font-size: 14px;
  letter-spacing: 0;
  color: var(--ink-muted);
  max-width: 380px;
  text-transform: none;
}

/* Utility ------------------------------------------------ */

.mono-small {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-muted);
}
.hairline { background: var(--rule); height: 1px; width: 100%; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 32px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 28px; }

@media (max-width: 820px) {
  .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; gap: 32px; }
  .nav-meta { display: none; }
  footer.foot .container { grid-template-columns: 1fr; }
}