:root {
  --bg: #f2efe8;
  --ink: #1b1b1b;
  --accent: #c04b35;
  --board-light: #f8f4ec;
  --board-dark: #b58863;
  --panel: #ffffff;
  --shadow: rgba(0, 0, 0, 0.08);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Georgia", "Times New Roman", serif;
  color: var(--ink);
  background: radial-gradient(circle at 20% 20%, #fff8ea 0%, var(--bg) 50%, #e6dfd0 100%);
}

.page {
  max-width: 1200px;
  margin: 0 auto;
  padding: 28px;
}

.hero {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
  margin-bottom: 24px;
}

.hero h1 {
  margin: 0 0 6px 0;
  font-size: 32px;
  letter-spacing: 0.5px;
}

.controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

button {
  background: var(--accent);
  color: white;
  border: none;
  padding: 10px 16px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 14px;
}

button:hover { filter: brightness(1.05); }

button.ghost {
  background: transparent;
  color: var(--ink);
  border: 1px solid #d0c8bb;
}

.github-btn {
  background: #111;
  color: #fff;
  border-radius: 8px;
  padding: 10px 16px;
  text-decoration: none;
  font-size: 14px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.github-btn:hover {
  filter: brightness(1.1);
}

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--panel);
  padding: 8px 12px;
  border-radius: 8px;
  box-shadow: 0 6px 18px var(--shadow);
  font-size: 14px;
}

.toggle input[type="number"] {
  width: 56px;
  padding: 4px 6px;
  border-radius: 6px;
  border: 1px solid #d0c8bb;
  font-family: inherit;
}

.toggle select {
  padding: 4px 6px;
  border-radius: 6px;
  border: 1px solid #d0c8bb;
  background: white;
  font-family: inherit;
}

.board-area {
  display: grid;
  grid-template-columns: minmax(280px, 520px) 1fr;
  gap: 24px;
}

.board-wrap {
  display: grid;
  grid-template-columns: 28px 1fr 28px;
  grid-template-rows: 28px 1fr 28px;
  align-items: stretch;
  justify-items: stretch;
  width: 100%;
  max-width: 520px;
}

.board {
  grid-column: 2;
  grid-row: 2;
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1;
  border-radius: 12px;
  overflow: hidden;
  box-shadow: 0 14px 30px var(--shadow);
  min-height: 280px;
}

@supports not (aspect-ratio: 1 / 1) {
  .board {
    height: 0;
    padding-bottom: 100%;
  }
}

.square-layer {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
  z-index: 1;
}

.piece-layer {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 2;
}

.square {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 36px;
  cursor: pointer;
  position: relative;
}

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

.square.selected {
  box-shadow: inset 0 0 0 3px var(--accent);
}

.square.move::before {
  content: "";
  position: absolute;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: rgba(192, 75, 53, 0.6);
}

.square.check {
  background-image:
    linear-gradient(45deg, transparent 46%, #f5c400 46%, #f5c400 54%, transparent 54%),
    linear-gradient(-45deg, transparent 46%, #f5c400 46%, #f5c400 54%, transparent 54%);
  background-size: 100% 100%;
  background-blend-mode: multiply;
}

.piece {
  position: absolute;
  width: 12.5%;
  height: 12.5%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 36px;
  transition: transform 320ms ease;
  will-change: transform;
}

.coord-row,
.coord-col {
  font-size: 12px;
  letter-spacing: 0.5px;
  color: #6d645a;
  text-transform: uppercase;
  display: grid;
  gap: 2px;
}

.coord-row {
  grid-column: 2;
  grid-template-columns: repeat(8, 1fr);
  align-items: center;
  text-align: center;
}

.coord-row.top {
  grid-row: 1;
  align-items: end;
}

.coord-row.bottom {
  grid-row: 3;
  align-items: start;
}

.coord-col {
  grid-row: 2;
  grid-template-rows: repeat(8, 1fr);
  align-items: center;
  text-align: center;
}

.coord-col.left {
  grid-column: 1;
  justify-items: end;
  padding-right: 4px;
}

.coord-col.right {
  grid-column: 3;
  justify-items: start;
  padding-left: 4px;
}

.side {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.panel {
  background: var(--panel);
  padding: 16px;
  border-radius: 12px;
  box-shadow: 0 10px 22px var(--shadow);
}

.panel h2 {
  margin-top: 0;
  font-size: 18px;
}

.moves {
  max-height: 240px;
  overflow-y: auto;
  padding-left: 20px;
  margin: 0;
}

.tips {
  margin: 0;
  padding-left: 18px;
}

.modal {
  position: fixed;
  inset: 0;
  background: rgba(12, 12, 12, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}

.modal.hidden {
  display: none;
}

.modal-card {
  background: var(--panel);
  padding: 20px;
  border-radius: 12px;
  width: min(360px, 90vw);
  box-shadow: 0 18px 40px var(--shadow);
}

.promo-choices {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
}

@media (max-width: 900px) {
  .board-area {
    grid-template-columns: 1fr;
  }

  .board-wrap {
    grid-template-columns: 20px 1fr 20px;
    grid-template-rows: 20px 1fr 20px;
  }
}