:root {
  color-scheme: dark;
  --bg: #050608;
  --panel: #11151a;
  --panel-2: #171b21;
  --text: #edf3ee;
  --muted: #9aa6a0;
  --border: #263038;
  --board-light: #eeeed2;
  --board-dark: #769656;
  --board-shadow: rgba(0, 0, 0, 0.38);
  --dot: #77d970;
  --dot-ring: rgba(119, 217, 112, 0.28);
  --accent: #a7e38f;
  --piece-shadow: drop-shadow(0 2px 4px rgba(0, 0, 0, 0.35));
  --board-gutter: clamp(16px, 1.6vw, 24px);
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  overscroll-behavior-y: none;
  touch-action: manipulation;
  background:
    radial-gradient(circle at top, rgba(118, 150, 86, 0.12), transparent 34%),
    linear-gradient(180deg, #090b0d 0%, #050608 100%);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

body {
  min-height: 100vh;
  overflow-x: hidden;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
}

.shell {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 1fr;
  gap: 24px;
  padding: 32px;
  max-width: 1400px;
  margin: 0 auto;
}

.card {
  background: linear-gradient(180deg, rgba(23, 27, 33, 0.96), rgba(14, 18, 22, 0.96));
  border: 1px solid rgba(255, 255, 255, 0.06);
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.35);
  backdrop-filter: blur(10px);
}

.panel {
  background: transparent;
  border: 0;
  box-shadow: none;
  backdrop-filter: none;
  padding: 0;
}

.panel--landing,
.panel--game {
  display: grid;
  gap: 18px;
  align-content: start;
}

.is-hidden {
  display: none !important;
}

.panel__header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 18px;
}

.panel__header--landing,
.panel__header--game {
  margin-bottom: 0;
}

.eyebrow {
  margin: 0 0 10px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--accent);
  font-size: 0.72rem;
}

h1,
h2,
p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0;
  font-size: clamp(2rem, 4vw, 3.2rem);
}

.page-title {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  margin: 0;
  font-size: clamp(2.4rem, 4vw, 3.6rem);
}

.page-title-row {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.page-title__logo {
  width: 1.05em;
  height: 1.05em;
  display: block;
}

.status {
  padding: 10px 14px;
  border-radius: 999px;
  background: rgba(118, 150, 86, 0.14);
  border: 1px solid rgba(118, 150, 86, 0.28);
  color: #ddf3d3;
  white-space: nowrap;
}

.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 8px;
}

.mode-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.mode-card {
  display: grid;
  place-items: center;
  min-height: 156px;
  padding: 22px;
  border-radius: 22px;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: linear-gradient(180deg, rgba(14, 18, 22, 0.96), rgba(11, 14, 18, 0.96));
  color: var(--text);
  text-align: center;
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background 120ms ease;
  font-size: clamp(1.3rem, 2vw, 1.7rem);
  font-weight: 700;
}

.mode-card--pve {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  justify-content: space-between;
  gap: 14px;
  padding: 18px 22px;
}

.mode-card__label {
  width: 100%;
  margin-top: 2px;
  text-align: center;
  font-size: clamp(1.2rem, 1.8vw, 1.6rem);
  font-weight: 700;
}

.mode-card__choices {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  width: 100%;
  margin-top: auto;
}

.mode-chip {
  appearance: none;
  border: 1px solid rgba(167, 227, 143, 0.24);
  background: rgba(15, 19, 23, 0.92);
  color: var(--text);
  min-width: 0;
  min-height: 70px;
  border-radius: 16px;
  padding: 14px 12px;
  font: inherit;
  font-size: clamp(0.95rem, 1.45vw, 1.15rem);
  font-weight: 700;
  line-height: 1.2;
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background 120ms ease;
}

.mode-chip:hover {
  transform: translateY(-1px);
  border-color: rgba(167, 227, 143, 0.42);
}

.mode-card:hover {
  transform: translateY(-2px);
  border-color: rgba(167, 227, 143, 0.36);
}

.about-card {
  margin-top: 8px;
  padding: clamp(22px, 3vw, 34px);
}

.about-card h2 {
  margin-bottom: 18px;
  font-size: clamp(1.55rem, 2.2vw, 2rem);
}

.markdown-content {
  color: #cbd5cf;
  line-height: 1.7;
}

.markdown-content h3,
.markdown-content h4 {
  margin: 24px 0 8px;
  color: var(--text);
}

.markdown-content p,
.markdown-content ul {
  margin-bottom: 14px;
}

.markdown-content ul {
  padding-left: 1.35rem;
}

.markdown-content li + li {
  margin-top: 6px;
}

.markdown-content a {
  color: var(--accent);
}

.about-loading,
.about-error {
  color: var(--muted);
}

.game-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(340px, 380px);
  gap: 12px;
  align-items: start;
}

.turn-strip {
  display: flex;
  align-items: center;
  justify-content: center;
  width: fit-content;
  min-height: 40px;
  padding: 8px 18px;
  margin-inline: auto;
  border-radius: 999px;
  background: rgba(118, 150, 86, 0.14);
  border: 1px solid rgba(118, 150, 86, 0.28);
  color: #ddf3d3;
  font-size: 1rem;
}

.toolbar__btn {
  appearance: none;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: #0f1317;
  color: var(--text);
  border-radius: 14px;
  padding: 12px 16px;
  font: inherit;
  cursor: pointer;
  transition: transform 120ms ease, border-color 120ms ease, background 120ms ease;
}

.toolbar__btn--inline {
  min-height: 1.05em;
  padding: 0.24em 0.55em;
  font-size: clamp(2.1rem, 4vw, 3.45rem);
  line-height: 1;
  font-weight: 700;
}

.toolbar__btn:hover {
  transform: translateY(-1px);
  border-color: rgba(167, 227, 143, 0.36);
}

.toolbar__btn--active {
  background: linear-gradient(180deg, rgba(118, 150, 86, 0.4), rgba(118, 150, 86, 0.2));
  border-color: rgba(167, 227, 143, 0.45);
}

.board-wrap {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
  width: min(100%, 760px);
  max-width: 100%;
  margin-inline: auto;
}

.board-body {
  display: grid;
  grid-template-columns: var(--board-gutter) minmax(0, 1fr);
  gap: 0;
  width: 100%;
  min-width: 0;
}

.board-axes--left {
  align-items: stretch;
  width: auto;
}

.board-axes {
  display: grid;
  gap: 0;
  color: #98a39c;
  font-size: clamp(0.9rem, 1.05vw, 1.15rem);
  user-select: none;
}

.board-axes--bottom {
  grid-template-columns: repeat(8, 1fr);
  /* Match the board's inner grid (inside its 1px border) exactly. */
  width: calc(100% - var(--board-gutter) - 2px);
  margin-left: calc(var(--board-gutter) + 1px);
}

.board-axes--left {
  grid-template-rows: repeat(8, 1fr);
  justify-items: center;
  align-items: center;
}

.board-axes--bottom {
  justify-items: center;
  align-items: center;
}

.board-axes span {
  display: grid;
  place-items: center;
  aspect-ratio: 1;
}

.board {
  width: 100%;
  flex: 1 1 auto;
  min-width: 0;
  aspect-ratio: 1;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  border-radius: 0;
  overflow: hidden;
  box-shadow: 0 20px 60px var(--board-shadow);
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: #0b0d0f;
}

.square {
  position: relative;
  display: grid;
  place-items: center;
  line-height: 1;
  user-select: none;
  cursor: pointer;
}

.square.light {
  background: var(--board-light);
}

.square.dark {
  background: var(--board-dark);
}

.square.selected {
  box-shadow: inset 0 0 0 4px rgba(255, 255, 255, 0.16);
}

.square.move::after,
.square.capture::after {
  content: "";
  position: absolute;
  inset: 50% auto auto 50%;
  transform: translate(-50%, -50%);
  border-radius: 999px;
  pointer-events: none;
}

.square.move::after {
  width: 22%;
  aspect-ratio: 1;
  background: var(--dot);
  box-shadow: 0 0 0 10px var(--dot-ring);
}

.square.capture::after {
  width: calc(100% - 18px);
  height: calc(100% - 18px);
  border: 5px solid var(--dot);
  box-shadow: 0 0 0 8px rgba(119, 217, 112, 0.16);
}

.square .piece {
  z-index: 1;
  pointer-events: none;
  width: 82%;
  height: 82%;
  object-fit: contain;
  filter: var(--piece-shadow);
}

.square.white-piece .piece {
  color: #f8f7f2;
  text-shadow: 0 2px 3px rgba(0, 0, 0, 0.35), 0 0 1px rgba(0, 0, 0, 0.35);
}

.square.black-piece .piece {
  color: #1a1d1d;
  text-shadow: 0 1px 1px rgba(255, 255, 255, 0.18);
}

.sidebar {
  display: grid;
  gap: 18px;
  align-content: start;
  max-width: none;
}

.card {
  border-radius: 24px;
  padding: 22px;
}

.card p:last-child {
  margin-bottom: 0;
}

.info-grid {
  display: grid;
  gap: 14px;
}

.info-grid div {
  display: grid;
  gap: 4px;
  padding: 12px 14px;
  border-radius: 16px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.05);
}

.info-grid span {
  color: var(--muted);
  font-size: 0.9rem;
}

.info-grid strong {
  font-size: 1.05rem;
}

.history-list {
  display: grid;
  gap: 10px;
  min-height: 120px;
  /* 12 rows at 44px plus the 11 gaps between them. */
  max-height: 638px;
  overflow-y: auto;
  align-content: start;
  scrollbar-gutter: stable;
  overscroll-behavior: none;
}

.toolbar__btn:disabled {
  opacity: 0.42;
  cursor: not-allowed;
  transform: none;
}

.history-empty {
  color: var(--muted);
  padding: 10px 0;
}

.history-row {
  display: grid;
  grid-template-columns: 40px 1fr 1fr;
  min-height: 44px;
  align-items: center;
  gap: 10px;
  padding: 10px 12px;
  border-radius: 14px;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.05);
}

.promotion-modal {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  z-index: 50;
}

.promotion-modal.is-hidden {
  display: none !important;
}

.promotion-modal__backdrop {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(4px);
}

.promotion-modal__panel {
  position: relative;
  z-index: 1;
  min-width: min(92vw, 320px);
  padding: 18px;
  border-radius: 20px;
  background: rgba(14, 18, 22, 0.98);
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow: 0 30px 80px rgba(0, 0, 0, 0.45);
}

.promotion-modal__panel h2 {
  margin-bottom: 12px;
}

.promotion-options {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.promotion-option {
  display: grid;
  place-items: center;
  gap: 8px;
  padding: 12px 8px;
  border-radius: 16px;
  background: #0f1317;
  border: 1px solid rgba(255, 255, 255, 0.08);
  color: var(--text);
  cursor: pointer;
}

.promotion-option img {
  width: 48px;
  height: 48px;
  object-fit: contain;
}

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

.history-move {
  font-weight: 600;
}

@media (min-width: 1081px) {
  .history-row {
    grid-template-columns: 44px minmax(112px, 1fr) minmax(112px, 1fr);
  }

  .history-move {
    white-space: nowrap;
  }
}

.site-footer {
  display: grid;
  grid-template-rows: max-content max-content;
  justify-items: center;
  align-content: start;
  gap: 10px;
  width: 100%;
  margin-top: 12px;
  padding: 24px 20px;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  color: #b8c3bd;
  text-align: center;
}

.site-footer p {
  margin: 0;
}

.github-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 196px;
  height: 40px;
  padding: 0 12px;
  border-radius: 8px;
  background: #1d232a;
  color: #fff;
  font-size: 0.92rem;
  font-weight: 700;
  text-decoration: none;
  transition: transform 120ms ease, background 120ms ease;
}

.github-link:hover {
  background: #252d36;
  transform: translateY(-1px);
}

@media (max-width: 1080px) {
  .shell {
    grid-template-columns: 1fr;
  }

  .game-layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    max-width: 100%;
  }

  .board {
    max-width: 680px;
  }

  .board-wrap {
    width: min(100%, calc(680px + var(--board-gutter)));
  }
}

@media (max-width: 1080px) and (orientation: portrait) {
  /* Keep the board itself aligned with the sidebar card. The rank labels
     occupy a gutter that extends to the left of both content blocks. */
  .board-wrap {
    width: calc(100% + var(--board-gutter));
    max-width: none;
    margin-left: calc(-1 * var(--board-gutter));
    margin-right: 0;
  }

  .board {
    max-width: none;
  }
}

@media (max-width: 760px) {
  :root {
    --board-gutter: clamp(14px, 4vw, 18px);
  }

  .shell {
    padding: 12px;
  }

  .panel {
    padding: 0;
  }

  .panel__header {
    flex-direction: column;
  }

  .page-title {
    font-size: clamp(2.1rem, 7vw, 2.8rem);
  }

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

  .board-body {
    gap: 0;
    grid-template-columns: var(--board-gutter) minmax(0, 1fr);
  }

  .board-axes--bottom {
    width: calc(100% - var(--board-gutter) - 2px);
    margin-left: calc(var(--board-gutter) + 1px);
  }

  .board-axes {
    font-size: 0.88rem;
  }
}