:root {
  --bg: #eef4fb;
  --panel: #ffffff;
  --panel-2: #f3f7fb;
  --text: #122033;
  --muted: #5f7288;
  --line: #c9d6e4;
  --accent: #1d9f55;
  --accent-2: #147a40;
  --warn: #f59e0b;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Trebuchet MS", Verdana, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at 12% 15%, rgba(29, 155, 84, 0.13), transparent 40%),
    radial-gradient(circle at 82% 12%, rgba(37, 99, 235, 0.1), transparent 42%),
    linear-gradient(180deg, #f7fbff 0%, #eef5fb 60%, #e8f0f8 100%);
  min-height: 100vh;
}

.app-shell {
  max-width: 1180px;
  margin: 0 auto;
  min-height: 100vh;
  padding: 1.25rem;
  display: grid;
  grid-template-columns: minmax(280px, 1fr) 340px;
  gap: 1rem;
  align-items: start;
}

.board-panel,
.controls-panel {
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.95), rgba(247, 250, 253, 0.97));
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 18px;
  box-shadow: 0 16px 34px rgba(15, 23, 42, 0.08);
}

.board-panel {
  padding: 1rem;
}

.panel-header h1 {
  margin: 0;
  font-size: 1.6rem;
}

.panel-header p {
  margin: 0.35rem 0 0.9rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.about-panel {
  margin: 0.95rem auto 0;
  width: min(100%, 700px);
  background: rgba(243, 247, 251, 0.95);
  border: 1px solid rgba(148, 163, 184, 0.18);
  border-radius: 14px;
  padding: 0.95rem 1rem;
}

.about-panel h2 {
  margin: 0 0 0.5rem;
  font-size: 1.25rem;
  letter-spacing: 0.01em;
}

.about-panel p {
  margin: 0.25rem 0;
  line-height: 1.45;
  color: #213248;
}

.about-panel strong {
  color: #091729;
}

.panel-footer {
  width: min(100%, 700px);
  margin: 0.85rem auto 0;
  padding: 0.8rem 0.1rem 0.1rem;
  border-top: 1px solid rgba(148, 163, 184, 0.2);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem 1rem;
}

.panel-footer p {
  margin: 0;
  color: var(--muted);
  font-size: 0.78rem;
  line-height: 1.35;
}

.panel-footer a {
  color: #2b4f86;
  text-decoration: none;
  font-weight: 600;
}

.panel-footer a:hover {
  text-decoration: underline;
}

.panel-footer-right {
  text-align: right;
}

.board-stage {
  position: relative;
  touch-action: none;
}

.piece-tray {
  width: min(100%, 700px);
  margin: 0 auto 0.55rem;
  display: flex;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.2rem 0.1rem;
  touch-action: none;
}

.tray-white {
  margin-top: 0.55rem;
  margin-bottom: 0.25rem;
}

.tray-piece {
  min-width: 52px;
  min-height: 52px;
  width: 52px;
  height: 52px;
  padding: 0;
  display: grid;
  place-items: center;
  cursor: grab;
  background-clip: padding-box;
}

.tray-piece:hover {
  transform: translateY(-1px);
}

.tray-piece:focus-visible {
  outline: 2px solid rgba(43, 79, 134, 0.35);
  outline-offset: 2px;
}

.board-setup-hint {
  width: min(100%, 700px);
  margin: 0.15rem auto 0;
  color: var(--muted);
  font-size: 0.82rem;
}

.chess-board {
  width: min(100%, 720px);
  margin: 0 auto;
}

.board-frame {
  width: min(100%, 700px);
  margin: 0 auto;
  background: #f1f6fb;
  border: 1px solid #d8e1eb;
  border-radius: 14px;
  padding: 0.6rem;
}

.coords-row {
  display: grid;
  grid-template-columns: 26px repeat(8, minmax(28px, 1fr)) 26px;
  align-items: center;
  color: var(--muted);
  font-size: 0.78rem;
  user-select: none;
}

.coords-row.top {
  margin-bottom: 0.35rem;
}

.coords-row.bottom {
  margin-top: 0.35rem;
}

.coord-cell {
  text-align: center;
}

.board-body {
  display: grid;
  grid-template-columns: 26px 1fr 26px;
  gap: 0.35rem;
  align-items: stretch;
}

.rank-col {
  display: grid;
  grid-template-rows: repeat(8, 1fr);
  gap: 0;
}

.rank-cell {
  display: grid;
  place-items: center;
  color: var(--muted);
  font-size: 0.78rem;
  user-select: none;
  aspect-ratio: 1 / 1;
}

.squares-grid {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  border: 2px solid #9fb2c7;
  border-radius: 8px;
  overflow: hidden;
}

.board-square {
  aspect-ratio: 1 / 1;
  display: grid;
  place-items: center;
  user-select: none;
  position: relative;
  touch-action: none;
}

.board-square.light {
  background: #f1e5b9;
}

.board-square.dark {
  background: #8fb170;
}

.board-square.highlight-from::after,
.board-square.highlight-to::after {
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.board-square.highlight-from::after {
  box-shadow: inset 0 0 0 4px rgba(29, 155, 84, 0.95);
}

.board-square.highlight-to::after {
  box-shadow: inset 0 0 0 4px rgba(214, 131, 20, 0.96);
}

.piece {
  min-width: 68%;
  min-height: 68%;
  display: grid;
  place-items: center;
  position: relative;
  border-radius: 8px;
  border: 2px solid currentColor;
  font-family: "Segoe UI Symbol", "Noto Sans Symbols 2", "Arial Unicode MS", sans-serif;
  font-size: clamp(1.1rem, 2.6vw, 1.9rem);
  font-weight: 700;
  line-height: 1;
  cursor: grab;
  box-shadow: 0 2px 0 rgba(0, 0, 0, 0.15);
}

.piece-icon {
  width: 76%;
  height: 76%;
  object-fit: contain;
  display: block;
  pointer-events: none;
}

.board-square .piece.board-piece {
  width: 100%;
  height: 100%;
  min-width: 0;
  min-height: 0;
  padding: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
}

.board-square .piece.board-piece.white-piece,
.board-square .piece.board-piece.black-piece {
  background: transparent;
  border-color: transparent;
  text-shadow: none;
}

.board-square .piece.board-piece .piece-icon {
  width: 88%;
  height: 88%;
}

.tray-piece {
  min-width: 52px;
  min-height: 52px;
  width: 52px;
  height: 52px;
  padding: 0;
  border-radius: 10px;
  flex: 0 0 auto;
}

.tray-piece .piece-icon {
  width: 78%;
  height: 78%;
}

.piece:active {
  cursor: grabbing;
}

.drag-origin-hidden {
  opacity: 0.25;
}

body.dragging-piece {
  user-select: none;
}

.pointer-drag-ghost {
  position: fixed;
  width: 56px;
  height: 56px;
  margin-left: -28px;
  margin-top: -28px;
  z-index: 9999;
  pointer-events: none;
  display: grid;
  place-items: center;
}

.pointer-drag-ghost .piece.board-piece {
  width: 100%;
  height: 100%;
}

.white-piece {
  color: #0f2135;
  background: #fff8df;
  border-color: #51657a;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.7);
}

.black-piece {
  color: #f5f8fc;
  background: #24364a;
  border-color: #102030;
  text-shadow: 0 1px 0 rgba(0, 0, 0, 0.55);
}

.piece::before {
  content: none;
}

.controls-panel {
  padding: 1rem;
  display: grid;
  gap: 0.9rem;
}

.control-card {
  background: rgba(243, 247, 251, 0.95);
  border: 1px solid rgba(148, 163, 184, 0.18);
  border-radius: 12px;
  padding: 0.85rem;
}

.label {
  display: block;
  font-weight: 700;
  margin-bottom: 0.4rem;
  font-size: 0.95rem;
}

textarea {
  width: 100%;
  resize: vertical;
  min-height: 72px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: #ffffff;
  color: var(--text);
  padding: 0.65rem 0.7rem;
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.88rem;
}

textarea:focus {
  outline: 2px solid rgba(29, 155, 84, 0.28);
  border-color: var(--accent);
}

select {
  width: 100%;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--text);
  padding: 0.65rem 0.7rem;
  font-weight: 600;
}

.radio-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0.35rem 0;
  cursor: pointer;
}

.actions {
  display: grid;
  gap: 0.55rem;
}

button {
  border: 0;
  border-radius: 10px;
  padding: 0.65rem 0.85rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 120ms ease, opacity 120ms ease;
}

button:hover {
  transform: translateY(-1px);
}

button:disabled {
  opacity: 0.65;
  cursor: not-allowed;
}

.primary-btn {
  background: linear-gradient(180deg, var(--accent), var(--accent-2));
  color: #02130a;
}

.secondary-btn {
  background: #dbe6f2;
  color: #0f172a;
}

.status-text {
  margin: 0;
  color: var(--muted);
  line-height: 1.35;
}

.best-move-text {
  margin: 0.5rem 0 0;
  font-size: 1rem;
}

.best-move-text span {
  color: #8a5a00;
  font-weight: 700;
}

.board-loading {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background: rgba(241, 246, 251, 0.78);
  border-radius: 14px;
  backdrop-filter: blur(2px);
}

.board-loading.hidden {
  display: none;
}

.board-loading-card {
  width: min(86%, 420px);
  background: rgba(255, 255, 255, 0.98);
  border: 1px solid #d5e0eb;
  border-radius: 12px;
  padding: 0.9rem;
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.12);
}

.board-loading-title {
  font-weight: 800;
  margin-bottom: 0.5rem;
}

.board-loading-subtitle {
  margin-top: 0.45rem;
  font-size: 0.85rem;
  color: var(--muted);
}

.board-loading-bar {
  height: 12px;
  border-radius: 999px;
  background: #e6eef7;
  overflow: hidden;
  border: 1px solid #d6e3ef;
}

.board-loading-bar-fill {
  height: 100%;
  width: 42%;
  border-radius: inherit;
  background: linear-gradient(90deg, #8ad7a4, #1d9f55, #8ad7a4);
  background-size: 220% 100%;
  animation: board-loading-slide 1.2s linear infinite;
  transition: width 160ms ease;
}

.board-loading-bar-fill.determinate {
  animation: none;
  background: linear-gradient(90deg, #8ad7a4, #1d9f55);
  background-size: 100% 100%;
}

@keyframes board-loading-slide {
  0% {
    transform: translateX(-70%);
    background-position: 0% 50%;
  }
  100% {
    transform: translateX(240%);
    background-position: 100% 50%;
  }
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
    min-height: auto;
  }

  .controls-panel {
    order: 2;
  }
}

@media (max-width: 640px) {
  .board-body {
    grid-template-columns: 18px 1fr 18px;
    gap: 0.2rem;
  }

  .coords-row {
    grid-template-columns: 18px repeat(8, minmax(20px, 1fr)) 18px;
    font-size: 0.68rem;
  }

  .rank-cell {
    font-size: 0.68rem;
  }

  .piece-tray {
    gap: 0.35rem;
  }

  .tray-piece {
    min-width: 44px;
    min-height: 44px;
    width: 44px;
    height: 44px;
    font-size: 1.35rem;
  }

  .pointer-drag-ghost {
    width: 52px;
    height: 52px;
    margin-left: -26px;
    margin-top: -26px;
  }

  .board-square .piece.board-piece .piece-icon {
    width: 90%;
    height: 90%;
  }

  .board-setup-hint {
    font-size: 0.76rem;
  }

  .panel-footer {
    flex-direction: column;
    align-items: flex-start;
  }

  .panel-footer-right {
    text-align: left;
  }
}