* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  background: #0b1020;
  color: #e7e9ee;
}

.top {
  padding: 18px 16px;
  border-bottom: 1px solid rgba(255,255,255,.08);
  background: rgba(255,255,255,.03);
}
h1 { margin: 0 0 10px; font-size: 20px; }

.controls {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  align-items: center;
}
label { display: flex; gap: 8px; align-items: center; }
select, button {
  padding: 8px 10px;
  border-radius: 10px;
  border: 1px solid rgba(255,255,255,.15);
  background: rgba(255,255,255,.06);
  color: #e7e9ee;
}
button { cursor: pointer; }
button:hover { background: rgba(255,255,255,.10); }

.hint { margin: 12px 0 0; opacity: .9; font-size: 14px; }

.main {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 16px;
  padding: 16px;
}
@media (max-width: 900px) {
  .main { grid-template-columns: 1fr; }
}

.board-wrap {
  display: grid;
  place-items: center;
}

.board {
  width: min(84vw, 520px);
  aspect-ratio: 1 / 1;
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  border-radius: 14px;
  overflow: hidden;
  box-shadow: 0 10px 40px rgba(0,0,0,.45);
  border: 1px solid rgba(255,255,255,.10);
}

.square {
  position: relative;
  display: grid;
  place-items: center;
  user-select: none;
  cursor: pointer;
  font-size: clamp(12px, 2vw, 14px);
}
.light { background: #d9dce3; color: #111; }
.dark  { background: #404656; color: #fff; }

.square .coord {
  position: absolute;
  left: 6px;
  bottom: 5px;
  font-size: 10px;
  opacity: .75;
}

.square.start {
  outline: 3px solid rgba(255, 215, 0, .85);
  outline-offset: -3px;
}
.square.move::after {
  content: "";
  width: 60%;
  height: 60%;
  border-radius: 14px;
  background: rgba(34, 197, 94, .45);
  outline: 2px solid rgba(34, 197, 94, .7);
}

.panel {
  padding: 14px;
  border-radius: 14px;
  border: 1px solid rgba(255,255,255,.10);
  background: rgba(255,255,255,.03);
  height: fit-content;
}
.panel h2 { margin: 0 0 10px; font-size: 16px; }
.panel ul { margin: 0 0 10px; padding-left: 18px; }
.panel li { margin: 6px 0; opacity: .95; }

.status {
  margin-top: 10px;
  padding: 10px;
  border-radius: 12px;
  background: rgba(255,255,255,.06);
  border: 1px solid rgba(255,255,255,.10);
  font-size: 14px;
}

.footer {
  padding: 14px 16px;
  border-top: 1px solid rgba(255,255,255,.08);
  opacity: .9;
  font-size: 13px;
}
.footer {
  text-align: center;
}

.footer a {
  color: #38bdf8;
  text-decoration: none;
  font-weight: 600;
  transition: 0.3s;
}

.footer a:hover {
  color: #7dd3fc;
  text-shadow: 0 0 6px rgba(56,189,248,0.6);
}