:root {
  color-scheme: dark;
  --bg: #0a0a0b;
  --surface: #121214;
  --surface-2: #19191c;
  --line: #262629;
  --line-strong: #363639;
  --fg: #f2f2f0;
  --muted: #8b8b90;
  --dim: #5c5c62;
  --tx: #ff9f00;
  --tx-rgb: 255, 159, 0;
  --tx-core: #ffd28a;
  --tx-ink: #1a0d04;
  --rx: #34d5c4;
  --rx-rgb: 52, 213, 196;
  --rx-core: #a9f2ea;
  --rx-ink: #04171a;
  --warn: #ffb454;
  --font-mark: "Silkscreen", "Courier New", monospace;
  --font-ui: "Space Grotesk", "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "SF Mono", Menlo, monospace;
}

* {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

body {
  margin: 0;
  min-height: 100dvh;
  padding: 3rem 1rem 2rem;
  background:
    radial-gradient(120% 40% at 50% -10%, rgba(var(--tx-rgb), 0.08), transparent
    60%),
    var(--bg);
  color: var(--fg);
  font-family: var(--font-ui);
  font-size: 15px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

body::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background: repeating-linear-gradient(
    to bottom,
    rgba(255, 255, 255, 0.025) 0 1px,
    transparent 1px 3px
  );
}

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

a:hover {
  color: #ffc75c;
}

/* Type */

.mark {
  font-family: var(--font-mark);
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.label {
  font-family: var(--font-mark);
  font-size: 10px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}

.label.tx {
  color: var(--tx);
  text-shadow: 0 0 6px rgba(var(--tx-rgb), 0.9), 0 0 18px rgba(var(--tx-rgb),
    0.45);
}

.label.rx {
  color: var(--rx);
  text-shadow: 0 0 6px rgba(var(--rx-rgb), 0.9), 0 0 18px rgba(var(--rx-rgb),
    0.45);
}

.mono {
  font-family: var(--font-mono);
  font-size: 13px;
}

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

/* Header */

.site-header {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  max-width: 40rem;
  margin: 0 auto 1.5rem;
}

.site-header h1 {
  margin: 0;
  font-family: var(--font-mark);
  font-weight: 700;
  font-size: 2.25rem;
  line-height: 1;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-shadow:
    0 0 2px #fff3dc,
    0 0 14px rgba(var(--tx-rgb), 0.9),
    0 0 44px rgba(var(--tx-rgb), 0.5);
}

.site-header h1 a {
  color: inherit;
}

.site-header.compact h1 {
  font-size: 1.25rem;
}

.site-header h1 .label {
  vertical-align: 0.5em;
  margin-left: 0.5rem;
}

.tagline {
  margin: 0;
  color: var(--muted);
}

.grid-floor {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  height: 260px;
  pointer-events: none;
  overflow: hidden;
  z-index: -1;
  -webkit-mask-image: linear-gradient(to bottom, transparent, black 60%);
  mask-image: linear-gradient(to bottom, transparent, black 60%);
}

.grid-floor::before {
  content: "";
  position: absolute;
  left: -50%;
  right: -50%;
  top: 0;
  bottom: -60px;
  background-image:
    linear-gradient(rgba(var(--tx-rgb), 0.35) 1px, transparent 1px),
    linear-gradient(90deg, rgba(var(--tx-rgb), 0.35) 1px, transparent 1px);
  background-size: 40px 40px;
  transform: perspective(300px) rotateX(62deg);
  transform-origin: 50% 0;
}

.grid-floor::after {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(
    70% 60% at 50% 100%,
    rgba(var(--tx-rgb), 0.28),
    transparent 70%
  );
}

/* Layout */

.stack {
  display: grid;
  gap: 1rem;
  max-width: 40rem;
  margin: 0 auto;
}

.row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.625rem;
  align-items: end;
}

.rule {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.rule::after {
  content: "";
  flex-grow: 1;
  height: 1px;
  background: var(--line);
}

/* Panels */

.card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.875rem;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1rem;
}

.card::before,
.card::after {
  content: "";
  position: absolute;
  width: 10px;
  height: 10px;
  border-color: var(--line-strong);
  border-style: solid;
}

.card::before {
  top: -1px;
  left: -1px;
  border-width: 1px 0 0 1px;
}

.card::after {
  bottom: -1px;
  right: -1px;
  border-width: 0 1px 1px 0;
}

.card.tx {
  border-top-color: rgba(var(--tx-rgb), 0.85);
  box-shadow:
    inset 0 1px 0 rgba(var(--tx-rgb), 0.7),
    inset 0 30px 50px -40px rgba(var(--tx-rgb), 0.55),
    0 0 44px -10px rgba(var(--tx-rgb), 0.35);
}

.card.tx::before {
  border-color: var(--tx);
  box-shadow: 0 0 8px rgba(var(--tx-rgb), 0.8);
}

.card.rx {
  border-top-color: rgba(var(--rx-rgb), 0.85);
  box-shadow:
    inset 0 1px 0 rgba(var(--rx-rgb), 0.7),
    inset 0 30px 50px -40px rgba(var(--rx-rgb), 0.55),
    0 0 44px -10px rgba(var(--rx-rgb), 0.35);
}

.card.rx::before {
  border-color: var(--rx);
  box-shadow: 0 0 8px rgba(var(--rx-rgb), 0.8);
}

.card.dashed {
  border-style: dashed;
  background: rgba(18, 18, 20, 0.7);
  align-items: center;
  text-align: center;
  padding: 1.75rem 1rem;
}

.card-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.card h2 {
  margin: 0;
  font-family: var(--font-mark);
  font-weight: 400;
  font-size: 10px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
}

.card.tx h2 {
  color: var(--tx);
  text-shadow: 0 0 6px rgba(var(--tx-rgb), 0.9), 0 0 18px rgba(var(--tx-rgb),
    0.45);
}

.card.rx h2 {
  color: var(--rx);
  text-shadow: 0 0 6px rgba(var(--rx-rgb), 0.9), 0 0 18px rgba(var(--rx-rgb),
    0.45);
}

.card p {
  margin: 0;
}

.link-card {
  flex-direction: row;
  align-items: center;
  gap: 0.875rem;
  color: var(--fg);
  padding: 0.875rem 1rem;
}

.link-card:hover {
  color: var(--fg);
  border-color: var(--line-strong);
}

.link-card .icon {
  display: inline-flex;
  width: 40px;
  height: 40px;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  background: var(--surface-2);
  color: var(--tx);
  flex-shrink: 0;
}

.link-card.rx .icon {
  color: var(--rx);
}

.link-card .text {
  display: flex;
  flex-direction: column;
  gap: 2px;
  flex-grow: 1;
}

.link-card strong {
  font-weight: 600;
}

.link-card small {
  font-size: 13px;
  color: var(--muted);
}

.link-card .chevron {
  color: var(--muted);
}

/* Facts */

.facts {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 0.375rem 1rem;
  margin: 0;
}

.facts dt {
  color: var(--muted);
  font-size: 13px;
}

.facts dd {
  margin: 0;
  font-family: var(--font-mono);
  font-size: 13px;
}

/* Controls */

label {
  display: flex;
  flex-direction: column;
  gap: 0.375rem;
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
}

input,
select {
  min-height: 44px;
  padding: 0 0.75rem;
  background: #08080a;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  color: var(--fg);
  font: 500 14px var(--font-mono);
}

select {
  appearance: none;
  padding-right: 2rem;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%238b8b90' stroke-width='2' stroke-linecap='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.625rem center;
  background-size: 14px;
}

input:focus-visible,
select:focus-visible {
  outline: none;
  border-color: var(--tx);
  box-shadow:
    0 0 0 1px var(--tx),
    0 0 18px rgba(var(--tx-rgb), 0.45),
    inset 0 0 12px rgba(var(--tx-rgb), 0.12);
}

button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  min-height: 44px;
  padding: 0 1.125rem;
  font: 500 14px var(--font-ui);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border: 1px solid var(--line-strong);
  border-radius: 2px;
  background: transparent;
  color: var(--fg);
  cursor: pointer;
}

button.tx,
button.rx {
  border-radius: 8px;
  corner-shape: bevel;
}

button.tx {
  background: var(--tx);
  border-color: var(--tx-core);
  color: var(--tx-ink);
  box-shadow:
    0 0 0 1px rgba(var(--tx-rgb), 0.9),
    0 0 14px rgba(var(--tx-rgb), 0.65),
    0 0 40px rgba(var(--tx-rgb), 0.35),
    inset 0 0 16px rgba(255, 255, 255, 0.3);
}

button.rx {
  background: var(--rx);
  border-color: var(--rx-core);
  color: var(--rx-ink);
  box-shadow:
    0 0 0 1px rgba(var(--rx-rgb), 0.9),
    0 0 14px rgba(var(--rx-rgb), 0.65),
    0 0 40px rgba(var(--rx-rgb), 0.35),
    inset 0 0 16px rgba(255, 255, 255, 0.3);
}

button.ghost-tx {
  border-color: rgba(var(--tx-rgb), 0.7);
  color: var(--tx);
  text-shadow: 0 0 8px rgba(var(--tx-rgb), 0.7);
  box-shadow:
    0 0 14px rgba(var(--tx-rgb), 0.25),
    inset 0 0 14px rgba(var(--tx-rgb), 0.12);
}

button.ghost-rx {
  border-color: rgba(var(--rx-rgb), 0.7);
  color: var(--rx);
  text-shadow: 0 0 8px rgba(var(--rx-rgb), 0.7);
  box-shadow:
    0 0 14px rgba(var(--rx-rgb), 0.25),
    inset 0 0 14px rgba(var(--rx-rgb), 0.12);
}

button:focus-visible {
  outline: 1px solid var(--fg);
  outline-offset: 2px;
}

button:disabled {
  opacity: 0.35;
  cursor: default;
  box-shadow: none;
  text-shadow: none;
}

/* Status */

.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
  background: var(--muted);
}

.dot.tx {
  background: var(--tx-core);
  box-shadow: 0 0 4px var(--tx), 0 0 12px var(--tx), 0 0 24px
    rgba(var(--tx-rgb), 0.6);
}

.dot.rx {
  background: var(--rx-core);
  box-shadow: 0 0 4px var(--rx), 0 0 12px var(--rx), 0 0 24px
    rgba(var(--rx-rgb), 0.6);
  animation: pulse 1.6s ease-in-out infinite;
}

@keyframes pulse {
  50% {
    opacity: 0.55;
    box-shadow: 0 0 2px var(--rx), 0 0 6px var(--rx);
  }
}

.readout {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 0.75rem;
  background: #08080a;
  border: 1px solid var(--line);
  border-radius: 2px;
}

.readout .status {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--rx);
  text-shadow: 0 0 8px rgba(var(--rx-rgb), 0.75);
}

.readout .value {
  display: flex;
  align-items: baseline;
  gap: 0.625rem;
  font-size: 13px;
  color: var(--muted);
}

.readout strong {
  font-family: var(--font-mono);
  font-size: 18px;
  color: var(--fg);
  text-shadow: 0 0 10px rgba(var(--rx-rgb), 0.7);
}

/* Media */

.qr {
  display: block;
  width: min(100%, 20rem);
  margin: 0.5rem auto 0;
  image-rendering: pixelated;
  border: 1px solid var(--line-strong);
  box-shadow: 0 0 30px rgba(var(--tx-rgb), 0.35);
}

.qr:not([width]) {
  display: none;
}

.camera {
  position: fixed;
  z-index: 10;
  inset: auto 0 0;
  width: 100%;
  height: 50dvh;
  object-fit: cover;
  background: #05050a;
  border-top: 1px solid rgba(var(--rx-rgb), 0.6);
  box-shadow: 0 0 24px rgba(var(--rx-rgb), 0.25);
}

.camera.mirrored {
  transform: scaleX(-1);
}

.camera-flip {
  position: fixed;
  z-index: 11;
  right: 1rem;
  bottom: calc(50dvh - 44px - 1rem);
  background: rgba(10, 10, 11, 0.7);
}

body:has(.camera:not([hidden])) {
  padding-bottom: 50dvh;
}

/* The exchange screen: the camera fills the page, the code floats on it. */

body.viewfinder {
  height: 100dvh;
  padding: 0;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

/* Each role owns one accent here: the host is all amber, the guest all teal. */
body.viewfinder.host {
  --rx: var(--tx);
  --rx-rgb: var(--tx-rgb);
  --rx-core: var(--tx-core);
  --rx-ink: var(--tx-ink);
}

body.viewfinder.guest {
  --tx: var(--rx);
  --tx-rgb: var(--rx-rgb);
  --tx-core: var(--rx-core);
  --tx-ink: var(--rx-ink);
}

.viewfinder .camera {
  inset: 0;
  height: 100%;
  z-index: 0;
  border: 0;
  box-shadow: none;
}

.vf-head,
.vf-code,
.vf-middle,
.vf-foot {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 40rem;
  margin-inline: auto;
}

.vf-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
  min-height: 56px;
  padding: 0 1rem;
  background: rgba(10, 10, 11, 0.8);
}

.vf-head h1 {
  margin: 0;
  font-family: var(--font-mark);
  font-weight: 700;
  font-size: 1.25rem;
  line-height: 1;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-shadow:
    0 0 2px var(--tx-core),
    0 0 14px rgba(var(--tx-rgb), 0.9),
    0 0 44px rgba(var(--tx-rgb), 0.5);
}

.vf-head h1 a {
  color: var(--tx);
}

.vf-code {
  width: min(220px, 60vw);
  margin: 1rem auto 0;
}

.vf-middle {
  flex: 1 1 auto;
  min-height: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 1.5rem;
  padding: 1rem;
}

.vf-middle p {
  margin: 0;
  text-align: center;
}

.vf-flip {
  margin-top: auto;
  align-self: flex-end;
  background: rgba(10, 10, 11, 0.7);
}

.vf-foot {
  background: rgba(8, 8, 10, 0.9);
  border-top: 1px solid var(--line);
}

.vf-status {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  min-height: 44px;
  padding: 0 1rem;
}

.vf-status #status {
  flex-grow: 1;
}

.vf-foot summary {
  display: flex;
  align-items: center;
  min-height: 44px;
  padding: 0 1rem;
  border-top: 1px solid var(--line);
  cursor: pointer;
}

.vf-foot .log {
  max-height: 40dvh;
  padding: 0 1rem 1rem;
}

.rx-text {
  color: var(--rx);
  text-shadow: 0 0 8px rgba(var(--rx-rgb), 0.75);
}

.tx-text {
  color: var(--tx);
  text-shadow: 0 0 8px rgba(var(--tx-rgb), 0.75);
}

.log {
  width: 100%;
  min-height: 0;
  max-height: none;
  padding: 0.75rem;
  background: #08080a;
  border: 1px solid var(--line);
}

.log {
  margin: 0;
  max-height: 16rem;
  overflow: auto;
  font-family: var(--font-mono);
  font-size: 11.5px;
  line-height: 1.6;
  color: #c4c4c6;
  white-space: pre-wrap;
}

/* Game boards and channel checkboxes */

/* Room left for the header, status, log, and the buttons under the board. */
.board {
  --size: min(100vw - 1.5rem, 100dvh - 20rem, 36rem);
  display: grid;
  grid-template: repeat(3, 1fr) / repeat(3, 1fr);
  width: var(--size);
  height: var(--size);
  gap: 6px;
  padding: 0.5rem;
}

.board button {
  height: auto;
  padding: 0;
  font: 700 min(2.5rem, calc(var(--size) / 7)) var(--font-mark);
  transition: opacity 400ms ease;
}

/* X is the host and O the guest on both phones, so marks read the palette from
   :root, where body.host and body.guest have not yet folded the accents. */
:root {
  --x: var(--tx);
  --x-rgb: var(--tx-rgb);
  --o: var(--rx);
  --o-rgb: var(--rx-rgb);
}

.board .x {
  --mark: var(--x);
  --mark-rgb: var(--x-rgb);
}

.board .o {
  --mark: var(--o);
  --mark-rgb: var(--o-rgb);
}

.board button.x,
.board button.o {
  color: var(--mark);
  animation: mark-in 220ms ease-out;
}

.board.over button:not(.win) {
  opacity: 0.3;
}

.board.draw button {
  animation: draw-fade 900ms ease-in-out both;
}

.board.draw button:nth-of-type(3n + 2) {
  animation-delay: 120ms;
}

.board.draw button:nth-of-type(3n) {
  animation-delay: 240ms;
}

/* A win is the one moment on the board worth a glow. */
.board button.win {
  border-color: rgba(var(--mark-rgb), 0.7);
  text-shadow: 0 0 10px rgba(var(--mark-rgb), 0.8);
  animation: win-pop 500ms ease-out 350ms both;
}

/* Checkers: 64 squares, playable on the dark diagonals only. */
.board.checkers {
  grid-template: repeat(8, 1fr) / repeat(8, 1fr);
  gap: 2px;
}

.board.checkers button {
  position: relative;
  min-height: 0;
  border: 0;
  border-radius: 0;
  background: var(--line);
}

.board.checkers button:disabled {
  background: transparent;
}

.board.checkers button.x::before,
.board.checkers button.o::before {
  content: "";
  position: absolute;
  inset: 13%;
  border: 2px solid var(--mark);
  border-radius: 50%;
  background: rgba(var(--mark-rgb), 0.25);
}

.board.checkers button.king::after {
  content: "";
  position: absolute;
  inset: 33%;
  border: 2px solid var(--mark);
  border-radius: 50%;
}

/* A neutral ring: the landing squares of a multi-jump hold no piece, so there
   is no --mark-rgb to tint, and a selection neither transmits nor listens. */
.board.checkers button.from {
  box-shadow: inset 0 0 0 2px var(--muted);
}

.board.checkers button.to:not(.x):not(.o)::before {
  content: "";
  position: absolute;
  inset: 35%;
  border-radius: 50%;
  background: var(--dim);
}

/* Tic-tac-toe's game-over dim would grey out the winner's pieces too, so on the
   checkers board only the empty squares fall back. */
.board.checkers.over button.x,
.board.checkers.over button.o {
  opacity: 1;
}

.board-code {
  position: absolute;
  z-index: 2;
  inset: 0;
  width: 100%;
  height: 100%;
  image-rendering: pixelated;
  border: 1px solid var(--line-strong);
  box-shadow: 0 0 30px rgba(var(--tx-rgb), 0.35);
  cursor: pointer;
}

.vf-top {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 40rem;
  margin-inline: auto;
  background: rgba(8, 8, 10, 0.9);
  border-bottom: 1px solid var(--line);
}

.vf-foot > details:first-child > summary {
  border-top: 0;
}

.strike {
  position: absolute;
  height: 4px;
  border-radius: 2px;
  background: var(--mark);
  box-shadow:
    0 0 8px rgba(var(--mark-rgb), 0.9),
    0 0 24px rgba(var(--mark-rgb), 0.5);
  transform-origin: 0 50%;
  translate: 0 -50%;
  pointer-events: none;
  animation: strike 400ms cubic-bezier(0.3, 0.7, 0.2, 1) both;
}

@keyframes mark-in {
  from {
    scale: 0.4;
    opacity: 0;
  }
}

@keyframes strike {
  from {
    scale: 0 1;
  }
}

@keyframes win-pop {
  50% {
    scale: 1.15;
  }
}

@keyframes draw-fade {
  40% {
    scale: 0.9;
    opacity: 0.3;
  }
  to {
    opacity: 0.3;
  }
}

@media (prefers-reduced-motion: reduce) {
  .board button,
  .strike {
    animation: none !important;
    transition: none;
  }
}

/* The settings menu drops out of the header over the board and the code. */
.viewfinder .vf-head {
  z-index: 20;
}

.vf-gear {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  list-style: none;
  border: 1px solid rgba(var(--tx-rgb), 0.7);
  border-radius: 2px;
  color: var(--tx);
  box-shadow:
    0 0 14px rgba(var(--tx-rgb), 0.25),
    inset 0 0 14px rgba(var(--tx-rgb), 0.12);
  cursor: pointer;
}

.vf-gear::-webkit-details-marker {
  display: none;
}

.vf-gear:focus-visible {
  outline: 1px solid var(--fg);
  outline-offset: 2px;
}

.vf-settings {
  position: fixed;
  inset: 56px 1rem auto auto;
  gap: 0.25rem;
  color: var(--fg);
}

/* A game's rule options, agreed before Start and again before a replay. */
.rules {
  width: min(100%, 20rem);
  gap: 0.25rem;
  color: var(--fg);
}

label.check {
  flex-direction: row;
  align-items: center;
  gap: 0.5rem;
  min-height: 44px;
  cursor: pointer;
}

.check input {
  width: 20px;
  height: 20px;
  min-height: 0;
  margin: 0;
  accent-color: var(--tx);
}