/* CircuitCoach site. Same design system as the simulator, per spec section 5:
   PCB green ground, copper accent, monospace for every readout. No gradients,
   no vertical accent bars, no decorative flourishes. */

:root {
  --pcb:        #14332B;
  --pcb-deep:   #0E241E;
  --pcb-raise:  #1B4034;
  --pcb-lift:   #235045;
  --copper:     #C08552;
  --copper-hi:  #D9A06B;
  --silk:       #EDEAE2;
  --silk-dim:   #C9CFC9;
  --solder:     #7C8983;
  --amber:      #E8A33D;
  --brick:      #B8493F;
  --edge:       #2A5648;
  --edge-soft:  #21473C;

  /* Solder grey and copper are correct as borders and fills, but at small text
     sizes they measure 3.75:1 and 4.37:1 on the PCB ground, under the 4.5:1
     WCAG AA floor. These lightened pairs are for small text only. */
  --solder-text: #96A19B;   /* 5.12:1 on --pcb */
  --copper-text: #C68F5E;   /* 4.87:1 on --pcb */

  --display: "Chakra Petch", "Eurostile", system-ui, sans-serif;
  --body:    "IBM Plex Sans", "Segoe UI", system-ui, sans-serif;
  --mono:    "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, monospace;

  --wrap: 1140px;
  --bar-h: 60px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--bar-h) + 12px); }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  background: var(--pcb);
  color: var(--silk);
  font-family: var(--body);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--copper-hi); text-decoration: none; }
a:hover { text-decoration: underline; }
code {
  font-family: var(--mono);
  font-size: .92em;
  color: var(--amber);
  background: var(--pcb-deep);
  border: 1px solid var(--edge-soft);
  border-radius: 3px;
  padding: 1px 5px;
}
em { font-style: italic; color: var(--silk-dim); }

.skip {
  position: absolute; left: -9999px; top: 0;
  background: var(--copper); color: var(--pcb-deep);
  padding: 10px 16px; z-index: 100;
}
.skip:focus { left: 8px; top: 8px; }

:focus-visible { outline: 2px solid var(--amber); outline-offset: 3px; }

/* ---------- top bar ---------- */

.bar {
  position: sticky; top: 0; z-index: 50;
  height: var(--bar-h);
  display: flex; align-items: center; justify-content: space-between;
  gap: 20px;
  padding: 0 24px;
  background: rgba(14, 36, 30, .94);
  border-bottom: 1px solid var(--edge);
  backdrop-filter: blur(6px);
}

.mark { display: flex; align-items: center; gap: 10px; }
.mark .led { width: 30px; height: 20px; flex: 0 0 auto; }
.mark.small .led { width: 25px; height: 17px; }
.wordmark {
  font-family: var(--display);
  font-weight: 700; font-size: 16px; letter-spacing: .11em;
  color: var(--silk);
}
.wordmark em { font-style: normal; color: var(--copper-text); }

.bar-nav { display: flex; align-items: center; gap: 26px; }
.bar-nav a {
  font-family: var(--mono);
  font-size: 12px; letter-spacing: .09em; text-transform: uppercase;
  color: var(--solder-text);
}
.bar-nav a:hover { color: var(--silk); text-decoration: none; }
.bar-nav a.here { color: var(--copper-text); }
.bar-cta {
  border: 1px solid var(--edge);
  border-radius: 3px;
  padding: 8px 14px;
  color: var(--silk) !important;
}
.bar-cta:hover { border-color: var(--copper); color: var(--copper-hi) !important; }

/* ---------- shared section frame ---------- */

section {
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 84px 24px;
}
.band {
  background: var(--pcb-deep);
  max-width: none;
  padding-left: max(24px, calc((100% - var(--wrap)) / 2));
  padding-right: max(24px, calc((100% - var(--wrap)) / 2));
}

h1, h2, h3 { font-family: var(--display); letter-spacing: .01em; line-height: 1.14; }
h1 { font-size: clamp(34px, 5.4vw, 60px); font-weight: 700; margin: 0 0 20px; }
h2 { font-size: clamp(25px, 3.2vw, 36px); font-weight: 600; margin: 0 0 12px; }
h3 { font-size: 20px; font-weight: 600; margin: 0 0 8px; }

.sub { color: var(--silk-dim); max-width: 66ch; margin: 0 0 40px; }
.kicker {
  font-family: var(--mono);
  font-size: 11px; letter-spacing: .18em; text-transform: uppercase;
  color: var(--solder-text);
  margin: 0 0 14px;
}

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

.hero { padding-top: 96px; padding-bottom: 76px; }
.eyebrow {
  font-family: var(--mono);
  font-size: 11.5px; letter-spacing: .14em; text-transform: uppercase;
  color: var(--copper-text);
  margin: 0 0 22px;
}
.lede { font-size: 19px; color: var(--silk-dim); max-width: 66ch; margin: 0 0 32px; }

.cta-row { display: flex; flex-wrap: wrap; gap: 12px; }
.btn {
  display: inline-block;
  font-family: var(--display);
  font-weight: 600; font-size: 14px; letter-spacing: .07em;
  padding: 13px 22px;
  border: 1px solid var(--edge);
  border-radius: 3px;
  color: var(--silk);
  background: transparent;
}
.btn:hover { border-color: var(--copper); color: var(--copper-hi); text-decoration: none; }
.btn-primary {
  background: var(--copper);
  border-color: var(--copper);
  color: var(--pcb-deep);
}
.btn-primary:hover { background: var(--copper-hi); border-color: var(--copper-hi); color: var(--pcb-deep); }

.hero-facts {
  list-style: none; margin: 44px 0 0; padding: 0;
  display: grid; grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1px; background: var(--edge-soft);
  border: 1px solid var(--edge-soft);
}
.hero-facts li {
  background: var(--pcb);
  padding: 14px 16px;
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--solder-text);
}
.hero-facts b {
  display: block;
  font-size: 26px; font-weight: 500;
  color: var(--copper);
  margin-bottom: 2px;
}

/* ---------- two column split ---------- */

.split { display: grid; grid-template-columns: 1fr 1fr; gap: 56px; }
.split p { color: var(--silk-dim); margin: 0 0 16px; }

/* ---------- video ---------- */

.video-wrap {
  border: 1px solid var(--edge);
  border-radius: 5px;
  overflow: hidden;
  background: #000;
  line-height: 0;
}
.video-wrap video { width: 100%; height: auto; display: block; }
/* Drive serves the demo, so the frame has to hold 16:9 itself rather than being
   sized by an intrinsic video. aspect-ratio keeps it correct at every width. */
.video-embed { position: relative; aspect-ratio: 16 / 9; }
.video-embed iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
  display: block;
}
.caption {
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--solder-text);
  margin: 14px 0 0;
}

/* ---------- tiers ---------- */

.tier {
  display: grid;
  grid-template-columns: minmax(0, 0.85fr) minmax(0, 1.15fr);
  gap: 48px;
  align-items: center;
  padding: 40px 0;
  border-top: 1px solid var(--edge-soft);
}
.tier.reverse { grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr); }
.tier.reverse .tier-text { order: 2; }
.tier-n {
  font-family: var(--mono);
  font-size: 11px; letter-spacing: .16em; text-transform: uppercase;
  color: var(--copper-text);
  margin: 0 0 8px;
}
.tier-text p { color: var(--silk-dim); margin: 0 0 14px; }
.readout {
  font-family: var(--mono) !important;
  font-size: 12.5px;
  color: var(--amber) !important;
  background: var(--pcb-deep);
  border: 1px solid var(--edge-soft);
  border-radius: 3px;
  padding: 9px 12px;
  overflow-x: auto;
  white-space: nowrap;
}
.tier figure { margin: 0; }
.tier img {
  width: 100%; height: auto; display: block;
  border: 1px solid var(--edge);
  border-radius: 5px;
}

/* ---------- tutor ---------- */

.tutor-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 340px;
  gap: 48px;
  align-items: center;
}
.ladder { list-style: none; margin: 0; padding: 0; }
.ladder li {
  padding: 20px 0;
  border-top: 1px solid var(--edge-soft);
}
.ladder li:first-child { border-top: 0; padding-top: 0; }
.ladder .step {
  font-family: var(--mono);
  font-size: 11px; letter-spacing: .16em; text-transform: uppercase;
  color: var(--solder-text);
  margin: 0 0 4px;
}
.ladder h3 { color: var(--copper); margin-bottom: 4px; }
.ladder p:last-child { color: var(--silk-dim); margin: 0; }

.tutor-shot { margin: 0; }
.tutor-shot img {
  width: 100%; height: auto; display: block;
  border: 1px solid var(--edge);
  border-radius: 5px;
}
.tutor-shot figcaption {
  font-size: 14px;
  color: var(--solder-text);
  margin-top: 12px;
}

/* ---------- engineering cards ---------- */

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1px;
  background: var(--edge-soft);
  border: 1px solid var(--edge-soft);
  margin-bottom: 64px;
}
.card { background: var(--pcb); padding: 26px 24px; }
.card h3 { color: var(--copper); }
.card p { color: var(--silk-dim); margin: 0; font-size: 15.5px; }

.faults-title { font-size: 22px; margin-bottom: 10px; }
.faults {
  list-style: none; margin: 0; padding: 0;
  display: flex; flex-wrap: wrap; gap: 8px;
}
.faults li {
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--silk-dim);
  background: var(--pcb-deep);
  border: 1px solid var(--edge-soft);
  border-radius: 3px;
  padding: 6px 11px;
}

/* ---------- closer ---------- */

.closer { text-align: center; padding-top: 40px; padding-bottom: 96px; }
.closer .sub { margin-left: auto; margin-right: auto; }
.closer .cta-row { justify-content: center; }

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

.foot {
  background: var(--pcb-deep);
  border-top: 1px solid var(--edge);
  padding: 52px 24px 64px;
}
.foot-grid {
  max-width: var(--wrap);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1.3fr 1fr 1fr;
  gap: 48px;
}
.foot-h {
  font-family: var(--mono);
  font-size: 11px; letter-spacing: .16em; text-transform: uppercase;
  color: var(--solder-text);
  margin: 0 0 12px;
}
.foot-note { font-size: 14px; color: var(--solder-text); margin: 14px 0 0; max-width: 46ch; }
.foot-links { list-style: none; margin: 0; padding: 0; }
.foot-links li { margin-bottom: 7px; font-size: 15px; }

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

@media (max-width: 900px) {
  .bar { padding: 0 16px; }
  .bar-nav a:not(.bar-cta) { display: none; }
  section { padding: 60px 18px; }
  .band { padding-left: 18px; padding-right: 18px; }
  .br-wide { display: none; }   /* let the headline wrap naturally */
  .hero { padding-top: 64px; }
  .split, .tier, .tutor-grid, .foot-grid { grid-template-columns: minmax(0, 1fr); gap: 32px; }
  .tier.reverse .tier-text { order: 0; }
  .hero-facts { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .foot { padding: 40px 18px 52px; }
}
@media (max-width: 460px) {
  body { font-size: 16px; }
  .hero-facts { grid-template-columns: minmax(0, 1fr); }
}