:root {
  --bg: #090b10;
  --bg-elev: #12151c;
  --bg-inset: #0b0d12;
  --bg-well: #171b24;
  --line: rgba(255, 255, 255, 0.08);
  --line-strong: rgba(255, 255, 255, 0.16);
  --amber: #f3b63a;
  --amber-soft: rgba(243, 182, 58, 0.14);
  --cyan: #4fd6c8;
  --cyan-soft: rgba(79, 214, 200, 0.14);
  --text: #f2f1ea;
  --muted: #9aa1ae;
  --dim: #6b7382;
  --danger: #ef6a5c;
  --plus: #f3b63a;
  --minus: #7aa2ff;
  --accent: var(--amber);
  --accent-soft: var(--amber-soft);
  --font-ui: "IBM Plex Sans", "Segoe UI", sans-serif;
  --font-display: Sora, "IBM Plex Sans", sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;
  --radius: 14px;
  --radius-sm: 10px;
  --shadow: 0 24px 60px rgba(0, 0, 0, 0.38);
}

body[data-drive="diff"] {
  --accent: var(--cyan);
  --accent-soft: var(--cyan-soft);
}

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

html {
  color-scheme: dark;
}

html,
body {
  margin: 0;
  min-height: 100%;
}

body {
  font-family: var(--font-ui);
  color: var(--text);
  line-height: 1.45;
  background-color: var(--bg);
  background-image:
    radial-gradient(900px 480px at 8% -8%, rgba(243, 182, 58, 0.1), transparent 55%),
    radial-gradient(800px 420px at 100% 0%, rgba(79, 214, 200, 0.08), transparent 50%);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.skip {
  position: absolute;
  left: -999px;
  top: 0;
}

.skip:focus {
  left: 12px;
  top: 12px;
  z-index: 20;
  background: var(--bg-elev);
  padding: 8px 12px;
  border-radius: 8px;
}

.shell {
  width: min(1120px, calc(100% - 32px));
  margin: 0 auto;
  padding: 22px 0 72px;
}

.top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  padding: 12px 4px 18px;
  margin-bottom: 18px;
  border-bottom: 1px solid var(--line);
}

.wordmark {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.05rem;
  letter-spacing: 0.16em;
  color: var(--text);
  text-decoration: none;
}

.wordmark span {
  color: var(--amber);
}

nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 4px;
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

nav a {
  color: var(--muted);
  text-decoration: none;
  padding: 6px 10px;
  border-radius: 999px;
}

nav a.is-active {
  color: var(--text);
  background: rgba(255, 255, 255, 0.06);
}

nav a:hover {
  color: var(--text);
  text-decoration: none;
}

.lede {
  margin: 0 0 22px;
}

.kicker {
  font-family: var(--font-display);
  font-size: 0.7rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 8px;
}

h1 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(1.85rem, 4vw, 2.55rem);
  letter-spacing: -0.03em;
  margin: 0 0 8px;
}

.lede p {
  margin: 0;
  max-width: 40rem;
  color: var(--muted);
}

.board {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.035), rgba(255, 255, 255, 0.015));
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 18px 18px 16px;
  margin-bottom: 22px;
}

.board-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
}

.board-toolbar + .board-toolbar {
  margin-top: -8px;
}

.seg {
  display: inline-flex;
  flex-wrap: wrap;
  padding: 4px;
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-radius: 999px;
}

.seg-btn {
  appearance: none;
  border: 0;
  background: transparent;
  color: var(--muted);
  font: inherit;
  font-size: 0.85rem;
  font-weight: 500;
  padding: 8px 14px;
  border-radius: 999px;
  cursor: pointer;
  pointer-events: auto;
  position: relative;
  z-index: 1;
}

.seg-btn.is-active {
  background: var(--accent);
  color: #14120c;
}

.z-ctrl {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
}

.z-pair {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 16px;
}

.z-block {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px 12px;
}

.z-fixed {
  gap: 10px;
}

.z-fixed-label {
  color: var(--muted);
  font-size: 0.85rem;
}

.z-fixed strong {
  font-family: var(--font-mono);
  font-size: 1.05rem;
  font-weight: 500;
}

.z-fixed-note {
  color: var(--dim);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.node-z {
  display: block;
  margin-top: 6px;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--accent);
}

@media (max-width: 640px) {
  .z-pair {
    grid-template-columns: 1fr;
  }
}

.z-field {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--muted);
  font-size: 0.85rem;
}

.z-field input {
  width: 4.6rem;
  background: var(--bg-inset);
  border: 1px solid var(--line);
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 0.95rem;
  padding: 8px 8px;
  border-radius: 8px;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.chip {
  min-width: 36px;
  padding: 7px 8px;
  background: var(--bg-well);
  border: 1px solid var(--line);
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  border-radius: 8px;
  cursor: pointer;
}

.chip.is-active {
  color: #14120c;
  background: var(--accent);
  border-color: var(--accent);
}

.schematic-stage {
  background:
    linear-gradient(rgba(255, 255, 255, 0.028) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255, 255, 255, 0.028) 1px, transparent 1px),
    var(--bg-inset);
  background-size: 20px 20px, 20px 20px, auto;
  border: 1px solid var(--line);
  border-radius: 12px;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin-bottom: 16px;
}

.schematic {
  margin: 0;
  padding: 16px 18px 18px;
  min-width: 680px;
}

.schematic.is-off,
.schematic[hidden] {
  display: none;
}

.schematic-cap {
  font-size: 0.7rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--dim);
  margin: 0 0 14px;
}

.blk {
  display: grid;
  column-gap: 0;
  position: relative;
}

.blk-se {
  grid-template-columns: 168px minmax(180px, 1fr) 176px;
  grid-template-rows: auto 88px auto;
}

.blk-diff {
  grid-template-columns: 176px minmax(200px, 1fr) 210px;
  grid-template-rows: auto 78px 78px auto;
}

.blk-shell {
  border: 1px solid var(--line-strong);
  border-radius: 12px;
  background: rgba(23, 27, 36, 0.92);
  pointer-events: none;
}

.blk-shell.src {
  grid-column: 1;
  grid-row: 1 / -1;
  box-shadow: inset 3px 0 0 var(--accent);
}

.blk-shell.dut {
  grid-column: 3;
  grid-row: 1 / -1;
  box-shadow: inset -3px 0 0 var(--accent);
}

.blk-head,
.blk-port,
.blk-foot,
.blk-bus,
.blk-midcap {
  position: relative;
  z-index: 1;
}

.blk-head {
  padding: 14px 14px 4px;
}

.src-head,
.src-port,
.src-foot {
  grid-column: 1;
}

.dut-head,
.dut-port,
.dut-foot {
  grid-column: 3;
}

.node-kicker {
  display: block;
  font-size: 0.64rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--dim);
}

.node-title {
  display: block;
  font-family: var(--font-display);
  font-size: 1.12rem;
  font-weight: 600;
  margin-top: 2px;
}

.node-sub {
  display: block;
  color: var(--muted);
  font-size: 0.78rem;
}

.blk-port {
  display: flex;
  z-index: 2;
  align-items: center;
  gap: 8px;
  padding: 0 14px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--muted);
}

.src-port {
  justify-content: flex-end;
}

.dut-port {
  justify-content: flex-start;
}

.blk-port em {
  font-style: normal;
}

.blk-port.plus,
.blk-port.plus em {
  color: var(--plus);
}

.blk-port.minus,
.blk-port.minus em {
  color: var(--minus);
}

.nub {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--bg-well);
  border: 2px solid var(--accent);
  box-shadow: 0 0 0 3px var(--bg-well);
  flex: 0 0 auto;
  position: relative;
}

.src-port .nub {
  margin-right: -19px;
}

.dut-port .nub {
  margin-left: -19px;
}

.plus .nub {
  border-color: var(--plus);
}

.minus .nub {
  border-color: var(--minus);
}

.blk-bus {
  display: grid;
  /* minmax(0, 1fr) keeps the outer rows equal so the wire stays on the nub centre line. */
  grid-template-rows: minmax(0, 1fr) auto minmax(0, 1fr);
  align-items: center;
  justify-items: center;
  min-width: 0;
  /* 8px is the nub radius plus its ring, so the wire meets each nub exactly. */
  padding: 0 8px;
  grid-column: 2;
}

.blk-bus .bus-tag.top,
.blk-bus .rail-tag {
  align-self: end;
  padding-bottom: 6px;
}

.blk-bus .bus-tag:last-child,
.blk-bus .rail-sub {
  align-self: start;
  padding-top: 6px;
}

.blk-se .src-head,
.blk-se .dut-head {
  grid-row: 1;
}

.blk-se .blk-bus {
  grid-row: 2;
}

.blk-se .src-port,
.blk-se .dut-port {
  grid-row: 2;
}

.blk-se .src-foot,
.blk-se .dut-foot {
  grid-row: 3;
}

.blk-diff .src-head,
.blk-diff .dut-head {
  grid-row: 1;
}

.blk-diff .src-port.plus,
.blk-diff .blk-bus.plus,
.blk-diff .dut-port.plus {
  grid-row: 2;
}

.blk-diff .src-port.minus,
.blk-diff .blk-bus.minus,
.blk-diff .dut-port.minus {
  grid-row: 3;
}

.blk-diff .src-foot,
.blk-diff .dut-foot {
  grid-row: 4;
}

.blk-midcap {
  grid-column: 1;
  grid-row: 2 / 4;
  align-self: center;
  justify-self: start;
  margin-left: 12px;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  color: var(--dim);
  background: var(--bg-well);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 3px 8px;
  z-index: 2;
}

.bus-tag,
.rail-tag,
.rail-sub {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--muted);
  text-align: center;
}

.bus-tag.top,
.rail-tag {
  color: var(--accent);
}

.blk-bus.plus .rail-tag {
  color: var(--plus);
}

.blk-bus.minus .rail-tag {
  color: var(--minus);
}

.bus-track {
  display: flex;
  align-items: center;
  width: 100%;
}

.wire {
  display: block;
  flex: 1;
  height: 2px;
  background: var(--accent);
  box-shadow: 0 0 10px color-mix(in srgb, var(--accent) 40%, transparent);
}

.arrow {
  width: 0;
  height: 0;
  border-top: 5px solid transparent;
  border-bottom: 5px solid transparent;
  border-left: 8px solid var(--accent);
}

.blk-bus.plus .wire {
  background: var(--plus);
  box-shadow: 0 0 10px color-mix(in srgb, var(--plus) 40%, transparent);
}

.blk-bus.plus .arrow {
  border-left-color: var(--plus);
}

.blk-bus.minus .wire {
  background: var(--minus);
  box-shadow: 0 0 10px color-mix(in srgb, var(--minus) 40%, transparent);
}

.blk-bus.minus .arrow {
  border-left-color: var(--minus);
}

.blk-foot {
  padding: 8px 14px 14px;
}

.dut-foot {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--muted);
}

.node-readout {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.node-readout span {
  font-size: 0.64rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--dim);
}

.node-readout strong {
  font-family: var(--font-mono);
  font-size: 1.05rem;
  font-weight: 500;
  color: var(--accent);
}

.gnd {
  width: 24px;
  height: 12px;
  color: var(--dim);
  margin-top: 8px;
}

.vopp-brace {
  position: relative;
  grid-column: 3;
  grid-row: 2 / 4;
  justify-self: end;
  align-self: stretch;
  width: 12px;
  margin: 12px 10px 12px 0;
  border: 1px solid var(--accent);
  border-left: 0;
  z-index: 2;
  pointer-events: none;
}

.vopp-callout {
  position: absolute;
  top: 50%;
  right: calc(100% + 8px);
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  font-size: 0.62rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--dim);
  line-height: 1.15;
  white-space: nowrap;
}

.vopp-callout strong {
  font-family: var(--font-mono);
  font-size: 0.92rem;
  font-weight: 500;
  letter-spacing: 0;
  text-transform: none;
  color: var(--accent);
}

.fields {
  display: grid;
  gap: 12px;
}

@media (min-width: 720px) {
  .fields {
    grid-template-columns: 1fr 1fr;
  }
}

.field {
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 12px 14px 14px;
}

.field-label {
  display: flex;
  justify-content: space-between;
  gap: 8px;
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 6px;
}

.field-row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.field input[type="text"] {
  flex: 1;
  min-width: 0;
  background: transparent;
  border: 0;
  outline: none;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: 500;
  line-height: 1.1;
  padding: 4px 0;
}

.unit,
.unit-select {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  color: var(--muted);
}

.unit-select {
  appearance: none;
  background: var(--bg-well);
  border: 1px solid var(--line);
  color: var(--text);
  padding: 7px 10px;
  border-radius: 8px;
  font: inherit;
  font-family: var(--font-mono);
  font-size: 0.9rem;
}

.step {
  width: 36px;
  height: 36px;
  flex: 0 0 36px;
  border: 1px solid var(--line);
  background: var(--bg-well);
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 1.1rem;
  border-radius: 8px;
  cursor: pointer;
}

.step:hover,
.unit-select:hover,
.chip:hover,
.seg-btn:hover,
.copy:hover,
.ghost:hover {
  border-color: var(--line-strong);
}

.step:focus-visible,
.chip:focus-visible,
.seg-btn:focus-visible,
.copy:focus-visible,
.ghost:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.step:active,
.chip:active,
.seg-btn:active {
  transform: translateY(1px);
}

.metrics {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  margin-top: 14px;
}

.metric {
  background: var(--bg-well);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px 12px;
  margin: 0;
}

.metric dt {
  font-size: 0.66rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--dim);
  margin: 0 0 4px;
}

.metric dd {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 1rem;
  color: var(--text);
}

.toolbar {
  display: flex;
  gap: 8px;
  margin-top: 14px;
}

.copy,
.ghost {
  appearance: none;
  background: transparent;
  color: var(--muted);
  border: 1px solid var(--line);
  padding: 8px 12px;
  font: inherit;
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  border-radius: 8px;
  cursor: pointer;
}

.copy.is-copied {
  color: var(--accent);
  border-color: var(--accent);
}

.layout {
  display: grid;
  gap: 16px;
}

@media (min-width: 900px) {
  .layout {
    grid-template-columns: 1fr 1fr;
    align-items: start;
  }
}

.panel,
.ref {
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 18px 18px;
}

.panel h2,
.ref h2 {
  font-family: var(--font-display);
  font-size: 0.78rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  margin: 0 0 12px;
}

.panel p,
.panel li {
  color: var(--muted);
  font-size: 0.92rem;
}

.panel ul {
  margin: 0;
  padding-left: 1.1rem;
}

.formula {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 12px 14px;
  margin: 0 0 12px;
  overflow-x: auto;
}

.formula .sym {
  color: var(--accent);
}

.ref {
  margin-top: 16px;
  padding-bottom: 8px;
}

.ref-head {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: baseline;
  margin-bottom: 8px;
}

.ref p {
  margin: 0;
  color: var(--dim);
  font-size: 0.8rem;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 0.88rem;
}

th,
td {
  text-align: left;
  padding: 9px 6px;
  border-bottom: 1px solid var(--line);
}

th {
  color: var(--dim);
  font-weight: 500;
  font-size: 0.7rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

td.num {
  color: var(--text);
}

.foot {
  margin-top: 28px;
  color: var(--dim);
  font-size: 0.8rem;
}

.toast {
  position: fixed;
  right: 16px;
  bottom: 16px;
  background: var(--bg-elev);
  border: 1px solid var(--accent);
  color: var(--text);
  padding: 10px 14px;
  font-size: 0.85rem;
  border-radius: 10px;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity 160ms ease, transform 160ms ease;
}

.toast.is-on {
  opacity: 1;
  transform: none;
}

.invalid input[type="text"] {
  color: var(--danger);
}

noscript {
  display: block;
  margin: 16px auto;
  width: min(1120px, calc(100% - 32px));
  border: 1px solid var(--danger);
  padding: 12px 14px;
  color: var(--text);
  border-radius: 10px;
}

@media (max-width: 640px) {
  .shell {
    width: min(1120px, calc(100% - 20px));
  }

  .field input[type="text"] {
    font-size: 1.5rem;
  }

  .metrics {
    grid-template-columns: 1fr;
  }

  .board {
    padding: 14px;
  }
}

.field.compact input[type="text"] {
  font-size: 1.45rem;
}

.ls-panel[hidden] {
  display: none;
}

.hint {
  color: var(--muted);
  font-size: 0.88rem;
  margin: 12px 0 0;
}

.board + .board {
  margin-top: 16px;
}

.thumbs td {
  color: var(--muted);
}

.thumbs td.num {
  color: var(--text);
}

.spec-svg {
  width: 100%;
  height: 88px;
  margin: 4px 0 12px;
}

.chart-wrap {
  margin-top: 16px;
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 12px 8px;
}

.chart-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 8px;
}

.chart-cap {
  margin: 0;
  color: var(--dim);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.chart-wrap svg {
  width: 100%;
  height: auto;
  display: block;
  cursor: crosshair;
}

.chart-wrap svg text {
  fill: var(--muted);
  font-family: var(--font-mono);
  font-size: 11px;
}

@media (prefers-reduced-motion: reduce) {
  .step:active,
  .chip:active,
  .seg-btn:active,
  .toast {
    transition: none;
    transform: none;
  }
}