/* Robotic Systems library — brand tokens sampled from the Robotic Systems design PDF. */
:root {
  --bg: #1C1C1C;
  --surface: #2B2B2B;
  --raised: #3A3A3A;
  --card: #403F3C;
  --line: #3A3A3A;
  --accent: #C9A832;
  --on-accent: #1C1C1C;
  --text: #FFFFFF;
  --text-2: #D8D0B9;
  --muted: #908C81;
  --warn: #E0873A;
  --danger: #E35D4F;
  --font: "Roboto Flex", Roboto, system-ui, sans-serif;
  --mono: "Roboto Mono", ui-monospace, monospace;
  --gutter: clamp(16px, 4vw, 56px);
  --max: 1280px;
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text); font: 400 17px/1.6 var(--font); -webkit-font-smoothing: antialiased; }
img { display: block; max-width: 100%; height: auto; }
a { color: inherit; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

.mono { font-family: var(--mono); font-size: 12px; letter-spacing: .08em; text-transform: uppercase; line-height: 1.4; }
.eyebrow { color: var(--accent); margin: 0 0 20px; }
.eyebrow a { text-decoration: none; }
.eyebrow a:hover { text-decoration: underline; }
.link { background: none; border: 0; padding: 0; font: inherit; color: var(--text-2); text-decoration: none; cursor: pointer; }
.link:hover { color: var(--accent); }

.display { margin: 0; font-weight: 850; font-stretch: 85%; text-transform: uppercase; letter-spacing: -.035em; line-height: .92;
  font-size: clamp(2.6rem, 7.4vw, 6.6rem); max-width: 14ch; text-wrap: balance; }
.display--md { font-size: clamp(2.1rem, 5vw, 4.2rem); max-width: 18ch; }
.h2 { margin: 0; font-weight: 800; font-stretch: 90%; text-transform: uppercase; letter-spacing: -.02em; line-height: 1; font-size: clamp(1.6rem, 3vw, 2.4rem); }
.lead { color: var(--text-2); font-size: clamp(1.05rem, 1.6vw, 1.25rem); max-width: 56ch; margin: 24px 0 0; }

.btn { display: inline-flex; align-items: center; min-height: 48px; padding: 0 22px; background: var(--accent); color: var(--on-accent);
  font-weight: 700; text-decoration: none; border: 2px solid var(--accent); transition: transform .15s ease, background .15s ease; }
.btn:hover { transform: translateY(-1px); background: #D9B83D; }
.btn:active { transform: translateY(0); }
.btn--ghost { background: transparent; color: var(--text); border-color: var(--raised); }
.btn--ghost:hover { background: transparent; border-color: var(--accent); }

/* Header */
.bar { position: sticky; top: 0; z-index: 10; display: grid; grid-template-columns: auto 1fr auto; align-items: center; gap: 32px;
  padding: 12px var(--gutter); background: var(--bg); border-bottom: 1px solid var(--line); }
.bar__nav { display: flex; gap: 28px; font-weight: 600; font-size: 15px; }
.bar__nav a { text-decoration: none; color: var(--text-2); padding: 6px 0; border-bottom: 2px solid transparent; }
.bar__nav a:hover, .bar__nav a[aria-current] { color: var(--text); border-color: var(--accent); }
.bar__user { display: flex; align-items: center; gap: 16px; font-size: 15px; }
.bar__user form { margin: 0; }
.bar__user .mono { color: var(--muted); }

/* Hero */
.hero { position: relative; min-height: min(88dvh, 860px); display: grid; grid-template-rows: 1fr auto; overflow: hidden; border-bottom: 1px solid var(--line); }
.hero__img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; filter: grayscale(.35) contrast(1.05) brightness(.62); }
.hero::after { content: ""; position: absolute; inset: 0; background: rgba(28, 28, 28, .45); }
.hero__contours { position: absolute; right: -8%; top: -6%; width: 78%; opacity: .14; z-index: 1; pointer-events: none; }
.hero__inner { position: relative; z-index: 2; align-self: end; padding: 96px var(--gutter) 56px; max-width: var(--max); width: 100%; margin: 0 auto; }
.hero__actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 36px; }
.hero__stats { position: relative; z-index: 2; display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin: 0; background: var(--line);
  border-top: 1px solid var(--line); }
.hero__stats div { background: rgba(28, 28, 28, .82); padding: 18px var(--gutter); display: flex; justify-content: space-between; gap: 12px; }
.hero__stats dt { color: var(--muted); }
.hero__stats dd { margin: 0; color: var(--text); }

/* Topics */
.topics { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; background: var(--line); border-bottom: 1px solid var(--line); }
.topic { background: var(--bg); padding: 28px var(--gutter) 32px; text-decoration: none; display: grid; gap: 10px; align-content: start; min-height: 190px;
  transition: background .2s ease; }
.topic:hover { background: var(--surface); }
.topic__n { color: var(--accent); }
.topic__name { font-weight: 800; font-size: 1.4rem; text-transform: uppercase; letter-spacing: -.01em; }
.topic__desc { color: var(--muted); font-size: 15px; line-height: 1.45; }

/* Sections and cards */
.section { padding: 72px var(--gutter); max-width: calc(var(--max) + 2 * var(--gutter)); margin: 0 auto; }
.section__head { display: flex; justify-content: space-between; align-items: end; gap: 16px; margin-bottom: 32px; padding-bottom: 16px; border-bottom: 2px solid var(--text); }
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); }
.card { background: var(--bg); text-decoration: none; display: grid; grid-template-rows: auto auto auto 1fr; gap: 10px; padding-bottom: 28px; transition: background .2s ease; }
.card:hover { background: var(--surface); }
.card__img { aspect-ratio: 8 / 5; width: 100%; object-fit: cover; filter: grayscale(.25); transition: filter .3s ease; }
.card:hover .card__img { filter: none; }
.card__meta { color: var(--accent); padding: 12px 22px 0; }
.card__title { font-weight: 750; font-size: 1.3rem; line-height: 1.2; padding: 0 22px; }
.card__summary { color: var(--muted); font-size: 15px; line-height: 1.5; padding: 0 22px; }
.empty { background: var(--bg); padding: 32px; color: var(--muted); margin: 0; grid-column: 1 / -1; }

/* App block */
.app { display: grid; grid-template-columns: 1.2fr 1fr; gap: 1px; background: var(--line); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.app > * { background: var(--surface); padding: 64px var(--gutter); }
.app__text p:not(.eyebrow) { color: var(--text-2); max-width: 52ch; margin: 20px 0 0; }
.app__steps { list-style: none; margin: 0; display: grid; gap: 1px; background: var(--line); padding: 0; }
.app__steps li { background: var(--surface); padding: 22px var(--gutter); display: flex; gap: 18px; align-items: baseline; font-size: 13px; color: var(--text); }
.app__steps span { color: var(--accent); }

/* Page head, chips */
.page-head, .guide__head, .gate { padding: 72px var(--gutter) 40px; max-width: calc(var(--max) + 2 * var(--gutter)); margin: 0 auto; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 36px; }
.chip { font-family: var(--mono); font-size: 12px; letter-spacing: .08em; text-transform: uppercase; text-decoration: none; color: var(--text-2);
  padding: 10px 14px; border: 1px solid var(--raised); }
.chip:hover { border-color: var(--text-2); }
.chip[aria-current] { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }

/* Guide */
.guide__head { padding-bottom: 48px; }
.meta { display: flex; flex-wrap: wrap; gap: 1px; background: var(--line); border: 1px solid var(--line); margin: 36px 0 0; width: fit-content; }
.meta div { background: var(--bg); padding: 12px 18px; }
.meta dt { color: var(--muted); }
.meta dd { margin: 4px 0 0; color: var(--text); }
.guide__cover { width: 100%; max-height: 72vh; object-fit: cover; filter: grayscale(.2); }
.guide__body { max-width: 760px; margin: 0 auto; padding: 64px 16px 96px; display: grid; gap: 28px; }
.block-heading { margin-top: 28px; padding-top: 20px; border-top: 2px solid var(--text); font-size: clamp(1.4rem, 2.4vw, 1.9rem); }
.prose p { margin: 0 0 1em; color: var(--text-2); }
.prose p:last-child { margin-bottom: 0; }
.prose b, .prose strong { color: var(--text); }
.figure { margin: 8px 0; }
.figure figcaption { color: var(--muted); padding-top: 10px; text-transform: none; letter-spacing: .02em; }
.callout { border-left: 4px solid var(--accent); background: var(--surface); padding: 20px 24px; }
.callout p { margin: 0; color: var(--text-2); }
.callout__kind { color: var(--accent) !important; margin-bottom: 8px !important; }
.callout__title { color: var(--text) !important; font-weight: 750; font-size: 1.1rem; margin-bottom: 6px !important; }
.callout--warning { border-color: var(--warn); } .callout--warning .callout__kind { color: var(--warn) !important; }
.callout--safety { border-color: var(--danger); } .callout--safety .callout__kind { color: var(--danger) !important; }
.steps { list-style: none; margin: 0; padding: 0; display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); }
.steps li { background: var(--bg); display: grid; grid-template-columns: 56px 1fr; gap: 12px; padding: 18px 20px; }
.steps__n { color: var(--accent); padding-top: 4px; }
.steps p { margin: 0; color: var(--text-2); }
.steps .steps__title { color: var(--text); font-weight: 700; margin-bottom: 4px; }
.checklist { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.checklist li { display: grid; grid-template-columns: 22px 1fr; gap: 12px; color: var(--text-2); }
.checklist li::before { content: ""; width: 14px; height: 14px; margin-top: 6px; border: 2px solid var(--accent); }
.specs { margin: 0; display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); }
.specs div { background: var(--surface); display: grid; grid-template-columns: 1fr 1fr; gap: 16px; padding: 14px 20px; }
.specs dt { color: var(--muted); }
.specs dd { margin: 0; font-weight: 600; }

/* Gate */
.gate { min-height: 60vh; }
.gate .btn { margin-top: 36px; }
.gate__error { color: var(--danger); margin: 20px 0 0; }

/* Footer */
.foot { border-top: 1px solid var(--line); padding: 36px var(--gutter); }
.foot__row { display: flex; align-items: center; gap: 28px; flex-wrap: wrap; }
.foot__row p { color: var(--muted); margin: 0; flex: 1; }
.foot__row a { color: var(--text-2); text-decoration: none; }

@media (max-width: 960px) {
  .topics { grid-template-columns: repeat(2, 1fr); }
  .cards { grid-template-columns: repeat(2, 1fr); }
  .app { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .bar { grid-template-columns: auto 1fr; gap: 12px 16px; }
  .bar__nav { grid-column: 1 / -1; grid-row: 2; gap: 20px; }
  .bar__user { justify-self: end; }
  .hero__stats { grid-template-columns: 1fr; }
  .topics, .cards { grid-template-columns: 1fr; }
  .topic { min-height: 0; }
  .section { padding: 56px var(--gutter); }
}
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }