/* ==========================================================================
   Play with AI — Tic-Tac-Toe
   Dark editorial theme, matching Lily's portfolio, with its light alternative
   (html[data-theme="light"], chosen with the portfolio's theme toggle).
   ========================================================================== */

:root {
  --bg: #121212;
  --bg-raised: #1b1b1b;
  --ink: #f3efe7;
  --ink-muted: #a9a399;
  --ink-faint: #6f6a62; /* 3.5:1 on --bg: decoration only, never small text */
  --rule: rgba(243, 239, 231, 0.14);
  --rule-strong: rgba(243, 239, 231, 0.32);
  --gold: #d6a23e;
  --gold-bright: #e9bd62;
  --red: #d9463b;
  --red-bright: #e8655a; /* --red lifted to 5.7:1 so it can be used for small text */

  --font-display: "Playfair Display", "Times New Roman", Georgia, serif;
  --font-sans: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --gutter: clamp(16px, 4vw, 32px);
  --radius: 2px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --focus-ring: 2px solid var(--gold-bright);
  --wash: rgba(243, 239, 231, 0.04);
  --strike-mid: rgba(243, 239, 231, 0.45);

  color-scheme: dark;
}

/* Light theme. Gold and red are deepened so text stays above 4.5:1; "bright"
   variants are the stronger (darker) ones here, since they mark emphasis. */
:root[data-theme="light"] {
  --bg: #f7f3ec;
  --bg-raised: #efe9de;
  --ink: #1d1a16;
  --ink-muted: #57514a;
  --ink-faint: #8a8378; /* decoration only, as in the dark theme */
  --rule: rgba(29, 26, 22, 0.14);
  --rule-strong: rgba(29, 26, 22, 0.32);
  --gold: #875a0a;
  --gold-bright: #6b4706;
  --red: #b0372c;
  --red-bright: #9a2e24;
  --wash: rgba(29, 26, 22, 0.04);
  --strike-mid: rgba(29, 26, 22, 0.3);

  color-scheme: light;
}

/* ---------- Base ---------------------------------------------------------- */

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

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  background: var(--bg);
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

button,
input {
  font: inherit;
  color: inherit;
}

strong {
  font-weight: 600;
  color: var(--ink);
}

::selection {
  background: rgba(214, 162, 62, 0.35);
  color: var(--ink);
}

.sr-only {
  position: absolute !important;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* Small uppercase mono labels: the UI's voice. */
.label {
  margin: 0;
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.75rem;
  line-height: 1.4;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

/* Tiny X and O used in the status line, scoreboard and controls. */
.glyph {
  width: 1em;
  height: 1em;
  flex: none;
  overflow: visible;
  fill: none;
  stroke-width: 2.6;
  stroke-linecap: round;
}

.glyph--x {
  stroke: var(--ink);
}

.glyph--o {
  stroke: var(--gold);
}

/* ---------- Page ---------------------------------------------------------- */

.page {
  width: 100%;
  max-width: 980px;
  margin: 0 auto;
  padding: clamp(20px, 4vw, 44px) var(--gutter) 32px;
}

.masthead__top {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 4px 24px;
  padding-top: 14px;
  border-top: 1px solid var(--rule-strong);
}

a.masthead__author {
  color: var(--ink-muted);
  text-decoration: none;
}

a.masthead__author:hover {
  color: var(--ink);
}

.masthead__title {
  margin: clamp(20px, 3vw, 30px) 0 0;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(2.125rem, 9vw, 4.5rem);
  line-height: 0.95;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  text-wrap: balance;
}

.masthead__subtitle {
  margin: 0.3em 0 0;
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(1.375rem, 3.2vw, 1.75rem);
  line-height: 1.2;
  color: var(--gold);
}

.masthead__dek {
  max-width: 38em;
  margin: 14px 0 0;
  font-size: 1.0625rem;
  color: var(--ink-muted);
  text-wrap: pretty;
}

/* Wide screens: headline on the left, standfirst beside it, so the board
   starts higher on the page. */
@media (min-width: 960px) {
  .masthead {
    display: grid;
    grid-template-columns: auto minmax(0, 1fr);
    column-gap: 56px;
  }

  .masthead__top {
    grid-column: 1 / -1;
  }

  .masthead__dek {
    grid-column: 2;
    grid-row: 2 / span 2;
    align-self: end;
    justify-self: end;
    max-width: 22em;
    margin: 0;
  }
}

.masthead > * {
  animation: rise 0.8s var(--ease) both;
}

.masthead > :nth-child(2) {
  animation-delay: 60ms;
}

.masthead > :nth-child(3) {
  animation-delay: 120ms;
}

.masthead > :nth-child(4) {
  animation-delay: 180ms;
}

/* ---------- Game layout ---------------------------------------------------- */

.game {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  row-gap: 44px;
  margin-top: clamp(32px, 4.5vw, 48px);
  animation: rise 0.8s var(--ease) 0.2s both;
}

.game__play,
.game__panel {
  width: 100%;
  max-width: 440px;
  min-width: 0;
  margin-inline: auto;
}

.game__panel {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

@media (min-width: 720px) {
  .game {
    grid-template-columns: minmax(0, 1fr) 248px;
    column-gap: 40px;
    align-items: start;
  }

  .game__play,
  .game__panel {
    max-width: none;
    margin: 0;
  }
}

@media (min-width: 900px) {
  .game {
    grid-template-columns: minmax(0, 480px) 288px;
    justify-content: space-between;
    column-gap: 56px;
  }
}

.notice {
  margin: 0 0 18px;
  padding: 12px 14px;
  border-left: 2px solid var(--red);
  background: var(--bg-raised);
  font-size: 0.875rem;
  color: var(--ink);
}

/* ---------- Status line ---------------------------------------------------- */

.status {
  display: flex;
  align-items: center;
  gap: 12px;
  min-height: 2.75rem;
  margin-bottom: 10px;
}

.status__glyph {
  position: relative;
  width: 28px;
  height: 28px;
  flex: none;
  font-size: 22px;
}

.status__glyph .glyph {
  position: absolute;
  inset: 3px;
  transition: opacity 0.25s ease, transform 0.4s var(--ease);
}

.status .glyph--o,
.status[data-state="thinking"] .glyph--x,
.status[data-state="loss"] .glyph--x {
  opacity: 0;
  transform: scale(0.6);
}

.status[data-state="thinking"] .glyph--o,
.status[data-state="loss"] .glyph--o {
  opacity: 1;
  transform: none;
}

.status[data-state="thinking"] .glyph--o circle {
  stroke-dasharray: 30 14;
  transform-box: fill-box;
  transform-origin: center;
  animation: spin 1.1s linear infinite;
}

.status[data-state="draw"] .glyph--x {
  transform: translateX(-6px) scale(0.78);
}

.status[data-state="draw"] .glyph--o {
  opacity: 1;
  transform: translateX(7px) scale(0.78);
}

.status__text {
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(1.375rem, 4.2vw, 1.75rem);
  line-height: 1.2;
  color: var(--ink);
}

.status__message {
  display: inline-block;
}

.status__message.is-new {
  animation: settle 0.35s var(--ease);
}

.status[data-state="loss"] .status__text {
  color: var(--gold-bright);
}

.status[data-state="draw"] .status__text {
  color: var(--ink-muted);
}

/* ---------- Board -------------------------------------------------------- */

.board {
  position: relative;
  display: flex;
  flex-direction: column;
  width: 100%;
  aspect-ratio: 1 / 1;
  container-type: inline-size; /* lets the score overlay scale with the board */
  -webkit-user-select: none;
  user-select: none;
  touch-action: manipulation;
}

.board__row {
  position: relative;
  z-index: 1;
  display: flex;
  flex: 1 1 0;
  min-height: 0;
}

.board__cell {
  display: flex;
  flex: 1 1 0;
  min-width: 0;
}

.board__grid,
.board__strike {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  overflow: visible;
  pointer-events: none;
}

/* The # is drawn in by hand, one stroke after another. */
.board__grid path {
  fill: none;
  stroke: var(--ink);
  stroke-opacity: 0.78;
  stroke-width: 2.2;
  stroke-linecap: round;
  stroke-dasharray: 1;
  stroke-dashoffset: 1;
  animation: draw 0.8s var(--ease) forwards;
  animation-delay: calc(240ms + var(--i) * 110ms);
}

.board__strike {
  z-index: 2;
  filter: drop-shadow(0 0 6px rgba(233, 189, 98, 0.4));
}

.board__strike path {
  fill: none;
  stroke: var(--gold-bright);
  stroke-width: 5.5;
  stroke-linecap: round;
  stroke-dasharray: 1;
  stroke-dashoffset: 1;
  animation: draw 0.55s cubic-bezier(0.65, 0, 0.35, 1) 0.15s forwards;
}

.cell {
  position: relative;
  flex: 1 1 0;
  min-width: 0;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 14px;
  background: transparent;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.cell:focus {
  outline: none;
}

.cell:focus-visible {
  outline: var(--focus-ring);
  outline-offset: -9px;
}

.cell[aria-disabled="true"] {
  cursor: default;
}

.board[data-turn="ai"] .cell {
  cursor: progress;
}

/* A faint X previews your move on hover / keyboard focus. */
.cell::before {
  content: "";
  position: absolute;
  inset: 0;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100' fill='none' stroke='%23f3efe7' stroke-width='5.6' stroke-linecap='round'%3E%3Cpath d='M29 28.5C41 40 57 56.5 71.5 71M71 29C59 40.5 42.5 57 28.5 71.5'/%3E%3C/svg%3E") center / 100% 100% no-repeat;
  opacity: 0;
  transition: opacity 0.18s ease;
  pointer-events: none;
}

@media (hover: hover) {
  .board[data-turn="human"][data-thinking="off"] .cell[aria-disabled="false"]:hover::before {
    opacity: 0.16;
  }
}

.board[data-turn="human"][data-thinking="off"] .cell[aria-disabled="false"]:focus-visible::before {
  opacity: 0.16;
}

.cell__mark {
  position: absolute;
  inset: 0;
  pointer-events: none;
  transition: opacity 0.5s var(--ease);
}

.mark {
  display: block;
  width: 100%;
  height: 100%;
  overflow: visible;
  fill: none;
  stroke-width: 5.6;
  stroke-linecap: round;
  stroke-linejoin: round;
  transform: rotate(var(--tilt, 0deg));
}

.mark path {
  stroke-dasharray: 1;
  stroke-dashoffset: 1;
  animation: draw 0.24s cubic-bezier(0.55, 0.1, 0.35, 1) forwards;
}

.mark--x {
  stroke: var(--ink);
}

.mark--x path:nth-child(2) {
  animation-delay: 0.16s;
}

.mark--o {
  stroke: var(--gold);
}

.mark--o path {
  animation-duration: 0.5s;
}

/* Round over: the winning three stay bright, the rest step back. */
.board[data-result="win"] .cell:not(.is-winning) .cell__mark,
.board[data-result="loss"] .cell:not(.is-winning) .cell__mark {
  opacity: 0.28;
}

.board[data-result="draw"] .cell__mark {
  opacity: 0.5;
}

/* ---------- "Show AI thinking" overlay ----------------------------------- */

.cell__eval {
  position: absolute;
  inset: 9%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  border-radius: 50%;
  pointer-events: none;
  opacity: 0;
  transform: scale(0.92);
  transition: opacity 0.25s ease, transform 0.35s var(--ease);
}

.cell__eval.is-shown {
  opacity: 1;
  transform: none;
}

.eval__score {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.25rem;
  font-size: clamp(1.25rem, 8.5cqi, 2.375rem);
  line-height: 1;
  font-variant-numeric: lining-nums tabular-nums;
}

.eval__label {
  display: inline-flex;
  align-items: center;
  gap: 0.45em;
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.625rem;
  font-size: clamp(0.625rem, 2.6cqi, 0.75rem);
  line-height: 1.2;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  white-space: nowrap;
  color: var(--ink-muted);
}

.cell__eval[data-tone="win"] .eval__score {
  color: var(--gold-bright);
}

.cell__eval[data-tone="draw"] .eval__score {
  color: var(--ink);
}

.cell__eval[data-tone="loss"] .eval__score {
  color: var(--red-bright);
}

.cell__eval[data-best] {
  background: radial-gradient(closest-side, rgba(214, 162, 62, 0.17), rgba(214, 162, 62, 0));
}

.cell__eval[data-best] .eval__label::before,
.best-mark {
  content: "";
  display: inline-block;
  width: 0.6em;
  height: 0.6em;
  flex: none;
  background: var(--gold);
  transform: rotate(45deg);
}

@media (hover: hover) {
  .board[data-turn="human"] .cell[aria-disabled="false"]:hover .cell__eval.is-shown {
    transform: scale(1.07);
  }
}

/* ---------- Actions ------------------------------------------------------ */

.actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-top: 22px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 20px;
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius);
  background: transparent;
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink);
  cursor: pointer;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease, box-shadow 0.4s var(--ease);
}

.btn:focus-visible {
  outline: var(--focus-ring);
  outline-offset: 3px;
}

.btn:active {
  transform: translateY(1px);
}

.btn--primary {
  border-color: var(--gold);
  background: var(--gold);
  color: var(--bg);
}

.btn--primary:hover {
  border-color: var(--gold-bright);
  background: var(--gold-bright);
}

/* When a round ends, "New round" glows a little. */
.game[data-state="over"] .btn--primary {
  box-shadow: 0 0 0 5px rgba(214, 162, 62, 0.18);
}

.btn--quiet {
  padding: 0 4px;
  border-color: transparent;
  color: var(--ink-muted);
  text-decoration: underline;
  text-decoration-color: var(--rule-strong);
  text-underline-offset: 5px;
}

.btn--quiet:hover {
  color: var(--ink);
  text-decoration-color: currentColor;
}

/* ---------- AI thinking panel ---------------------------------------------- */

.thinking {
  margin-top: 30px;
  padding-top: 18px;
  border-top: 1px solid var(--rule);
  animation: rise 0.45s var(--ease);
}

.thinking[hidden] {
  display: none;
}

.thinking__head {
  display: grid;
  gap: 6px;
}

.thinking__title {
  color: var(--gold-bright);
}

.thinking__mode {
  margin: 0;
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1.125rem;
  line-height: 1.4;
  color: var(--ink);
}

.scale {
  margin: 20px 0 0;
}

.scale__bar {
  position: relative;
  height: 4px;
  border-radius: 2px;
  background: linear-gradient(90deg, var(--red) 0%, rgba(217, 70, 59, 0.2) 44%, var(--strike-mid) 50%, rgba(214, 162, 62, 0.2) 56%, var(--gold) 100%);
}

.scale__zero {
  position: absolute;
  top: -5px;
  left: 50%;
  width: 1px;
  height: 14px;
  background: var(--ink-muted);
}

.scale__labels {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: baseline;
  gap: 8px;
  margin-top: 10px;
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.6875rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

.scale__stop b {
  margin: 0 0.3em;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 1.0625rem;
  letter-spacing: 0;
}

.scale__stop--loss b {
  margin-left: 0;
  color: var(--red-bright);
}

.scale__stop--draw {
  text-align: center;
}

.scale__stop--draw b {
  color: var(--ink);
}

.scale__stop--win {
  text-align: right;
}

.scale__stop--win b {
  margin-right: 0;
  color: var(--gold-bright);
}

.thinking__note {
  margin: 18px 0 0;
  font-size: 0.875rem;
  line-height: 1.6;
  color: var(--ink-muted);
}

.thinking__key {
  display: block;
  margin-top: 8px;
}

.thinking__key .best-mark {
  margin: 0 0.4em 0 0.15em;
  vertical-align: 0.05em;
}

.lastmove {
  margin-top: 16px;
  padding: 14px 16px;
  border-left: 2px solid var(--gold);
  background: var(--bg-raised);
}

.lastmove .label {
  font-size: 0.6875rem;
}

.lastmove__text {
  margin: 6px 0 0;
  font-size: 0.9375rem;
  line-height: 1.55;
  color: var(--ink);
}

.lastmove__text strong {
  font-weight: 600;
}

.pill {
  display: inline-block;
  min-width: 2.2em;
  padding: 0 0.45em;
  border: 1px solid currentColor;
  border-radius: 999px;
  font-family: var(--font-display);
  font-weight: 700;
  font-variant-numeric: lining-nums tabular-nums;
  line-height: 1.45;
  text-align: center;
}

.pill[data-tone="win"] {
  color: var(--gold-bright);
}

.pill[data-tone="draw"] {
  color: var(--ink);
}

.pill[data-tone="loss"] {
  color: var(--red-bright);
}

/* ---------- Scoreboard ----------------------------------------------------- */

.scoreboard__title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin: 0;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--rule);
  font-size: inherit;
  font-weight: inherit;
}

.scoreboard__level {
  color: var(--gold-bright);
}

.scoreboard__grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  margin: 0;
}

.scoreboard__item {
  min-width: 0;
  padding: 14px 0 0 14px;
  border-left: 1px solid var(--rule);
}

.scoreboard__item:first-child {
  padding-left: 0;
  border-left: 0;
}

.scoreboard dt {
  display: flex;
  align-items: center;
  gap: 6px;
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.6875rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

.scoreboard dt .glyph {
  font-size: 12px;
  stroke-width: 3;
}

.scoreboard dd {
  margin: 6px 0 0;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(2.25rem, 5vw, 2.75rem);
  line-height: 1;
  font-variant-numeric: lining-nums tabular-nums;
  color: var(--ink);
}

.scoreboard__item--ai dd {
  color: var(--gold);
}

.scoreboard__item--draws dd {
  color: var(--ink-muted);
}

.is-bumped {
  animation: bump 0.6s var(--ease);
}

/* ---------- Controls ------------------------------------------------------- */

.control {
  min-width: 0;
  margin: 0;
  padding: 0;
  border: 0;
}

.control__legend {
  margin: 0 0 10px;
  padding: 0;
}

.segmented {
  display: grid;
  grid-template-columns: repeat(var(--segments, 2), minmax(0, 1fr));
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius);
}

.segment {
  position: relative;
  display: flex;
  min-width: 0;
}

.segment + .segment {
  border-left: 1px solid var(--rule-strong);
}

.segment input {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: 0;
  opacity: 0;
  pointer-events: none;
}

.segment__face {
  display: flex;
  flex: 1;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start; /* names line up even when one caption wraps */
  gap: 3px;
  min-height: 58px;
  padding: 11px 6px 10px;
  text-align: center;
  cursor: pointer;
  transition: background-color 0.2s ease, box-shadow 0.2s ease;
}

.segment__face--row {
  flex-direction: row;
  justify-content: center;
  gap: 8px;
  min-height: 46px;
}

.segment__face .glyph {
  font-size: 13px;
}

.segment__name {
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.75rem;
  line-height: 1.2;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-muted);
  transition: color 0.2s ease;
}

.segment__caption {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 0.8125rem;
  line-height: 1.25;
  color: var(--ink-muted);
  transition: color 0.2s ease;
}

.segment:hover .segment__face {
  background: var(--wash);
}

.segment:hover .segment__name {
  color: var(--ink);
}

.segment input:checked + .segment__face {
  background: rgba(214, 162, 62, 0.1);
  box-shadow: inset 0 0 0 1px var(--gold), inset 0 3px 0 var(--gold);
}

.segment input:checked + .segment__face .segment__name {
  color: var(--ink);
}

.segment input:checked + .segment__face .segment__caption {
  color: var(--gold-bright);
}

.segment input:focus-visible + .segment__face {
  position: relative;
  z-index: 1;
  outline: var(--focus-ring);
  outline-offset: 2px;
}

.switch {
  position: relative;
}

.switch__input {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: 0;
  opacity: 0;
}

.switch__label {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  min-height: 44px;
  cursor: pointer;
}

.switch__track {
  position: relative;
  width: 42px;
  height: 24px;
  flex: none;
  border: 1px solid var(--ink-muted);
  border-radius: 999px;
  transition: background-color 0.25s ease, border-color 0.25s ease;
}

.switch__thumb {
  position: absolute;
  top: 4px;
  left: 4px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--ink-muted);
  transition: transform 0.3s var(--ease), background-color 0.25s ease;
}

.switch__text {
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 0.75rem;
  line-height: 1.3;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink);
}

.switch__label:hover .switch__track {
  border-color: var(--ink);
}

.switch__input:checked + .switch__label .switch__track {
  border-color: var(--gold);
  background: var(--gold);
}

.switch__input:checked + .switch__label .switch__thumb {
  background: var(--bg);
  transform: translateX(18px);
}

.switch__input:focus-visible + .switch__label .switch__track {
  outline: var(--focus-ring);
  outline-offset: 3px;
}

.switch__hint {
  margin: 0 0 0 54px;
  font-size: 0.8125rem;
  line-height: 1.5;
  color: var(--ink-muted);
}

/* ---------- How the AI works ---------------------------------------------- */

.explainer {
  margin-top: clamp(56px, 9vw, 104px);
  border-top: 1px solid var(--rule-strong);
  border-bottom: 1px solid var(--rule);
}

.explainer__summary {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  grid-template-areas:
    "kicker icon"
    "title icon";
  align-items: center;
  gap: 6px 20px;
  padding: 22px 0;
  list-style: none;
  cursor: pointer;
}

.explainer__summary::-webkit-details-marker {
  display: none;
}

.explainer__summary::marker {
  content: "";
}

.explainer__summary:focus-visible {
  outline: var(--focus-ring);
  outline-offset: 4px;
}

.explainer__kicker {
  grid-area: kicker;
}

.explainer__title {
  grid-area: title;
  margin: 0;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(1.5rem, 4vw, 2.25rem);
  line-height: 1.1;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.explainer__icon {
  grid-area: icon;
  position: relative;
  width: 44px;
  height: 44px;
  flex: none;
  border: 1px solid var(--rule-strong);
  border-radius: 50%;
  transition: border-color 0.2s ease;
}

.explainer__icon::before,
.explainer__icon::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 14px;
  height: 1.5px;
  background: var(--ink);
  transform: translate(-50%, -50%);
  transition: transform 0.35s var(--ease);
}

.explainer__icon::after {
  transform: translate(-50%, -50%) rotate(90deg);
}

.explainer__details[open] .explainer__icon::after {
  transform: translate(-50%, -50%) rotate(0deg);
}

.explainer__summary:hover .explainer__icon {
  border-color: var(--gold);
}

.explainer__body {
  padding: 4px 0 40px;
}

.explainer__details[open] .explainer__body {
  animation: rise 0.5s var(--ease);
}

.explainer__intro {
  max-width: 36em;
  margin: 0 0 30px;
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(1.125rem, 2.4vw, 1.375rem);
  line-height: 1.45;
  color: var(--ink);
}

.explainer__grid {
  display: grid;
  gap: 28px;
}

@media (min-width: 860px) {
  .explainer__grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 40px;
  }
}

.strategy {
  padding-top: 16px;
  border-top: 1px solid var(--rule);
}

.strategy__num {
  color: var(--gold-bright);
}

.strategy__name {
  margin: 8px 0 10px;
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.25rem;
  line-height: 1.25;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.strategy p:not(.label) {
  margin: 0;
  font-size: 0.9375rem;
  line-height: 1.65;
  color: var(--ink-muted);
}

.explainer__scores {
  margin-top: 36px;
  padding: 18px 20px;
  border-left: 2px solid var(--gold);
  background: var(--bg-raised);
}

.explainer__scores p {
  max-width: 62em;
  margin: 8px 0 0;
  font-size: 0.9375rem;
  line-height: 1.65;
  color: var(--ink-muted);
}

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

.colophon {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 4px 24px;
  margin-top: 20px;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

.colophon p {
  margin: 0;
}

.colophon__links {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0 22px;
}

.colophon__link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  min-height: 44px;
  color: var(--ink);
  text-decoration: underline;
  text-decoration-color: var(--rule-strong);
  text-underline-offset: 5px;
  transition: color 0.2s ease;
}

.colophon__link svg {
  width: 12px;
  height: 12px;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.6;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.colophon__link:hover {
  color: var(--gold-bright);
  text-decoration-color: currentColor;
}

.colophon__link:focus-visible {
  outline: var(--focus-ring);
  outline-offset: 4px;
}

/* ---------- Embed mode (?embed=1): just the game, for an iframe ---------- */

/* The page keeps its --bg (identical in every browser, whatever the host's
   color-scheme); ?embed=1&bg=transparent lets the host page show through. */
.is-transparent,
.is-transparent body {
  background: transparent;
}

.is-embed body {
  min-height: 0;
}

.is-embed .page {
  max-width: none;
  padding: 6px; /* room for focus rings at the edges, no outer margin */
}

.is-embed .masthead,
.is-embed .explainer,
.is-embed .colophon {
  display: none;
}

.is-embed .game {
  margin-top: 0;
}

@media (min-width: 600px) {
  .is-embed .game {
    grid-template-columns: minmax(0, 1fr) 240px;
    column-gap: 32px;
    align-items: start;
  }

  .is-embed .game__play,
  .is-embed .game__panel {
    max-width: none;
    margin: 0;
  }
}

@media (min-width: 900px) {
  .is-embed .game {
    grid-template-columns: minmax(0, 480px) 288px;
    justify-content: center;
    column-gap: 56px;
  }
}

/* ---------- High-contrast (forced colors) ---------------------------------------- */

/* SVG strokes and box-shadows aren't recoloured by the system, so map them to
   system colors; otherwise a light high-contrast theme would hide the board. */
@media (forced-colors: active) {
  .board__grid path,
  .mark--x,
  .glyph--x {
    stroke: CanvasText;
  }

  .mark--o,
  .glyph--o {
    stroke: LinkText;
  }

  .board__strike {
    filter: none;
  }

  .board__strike path {
    stroke: Highlight;
  }

  .segment input:checked + .segment__face {
    outline: 2px solid Highlight;
    outline-offset: -4px;
  }

  .switch__thumb,
  .switch__track,
  .best-mark,
  .cell__eval[data-best] .eval__label::before,
  .scale__bar {
    forced-color-adjust: none;
  }

  .switch__thumb,
  .best-mark,
  .cell__eval[data-best] .eval__label::before,
  .scale__bar {
    background: CanvasText;
  }

  .switch__track {
    border-color: CanvasText;
  }

  .switch__input:checked + .switch__label .switch__track {
    border-color: Highlight;
    background: Highlight;
  }

  .switch__input:checked + .switch__label .switch__thumb {
    background: Canvas;
  }
}

/* ---------- Motion -------------------------------------------------------------- */

@keyframes draw {
  to {
    stroke-dashoffset: 0;
  }
}

@keyframes rise {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
}

@keyframes settle {
  from {
    opacity: 0;
    transform: translateY(4px);
  }
}

@keyframes bump {
  from {
    opacity: 0.15;
    transform: translateY(8px);
  }
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-delay: 0s !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    transition-delay: 0s !important;
    scroll-behavior: auto !important;
  }
}