:root {
  --bg-dark: #111520;
  --card-dark: #282e37;
  --text-light: #f8fafc;
  --text-subtle: #94a3b8;
  --accent: #8b5cf6;
  --accent-hover: #7c3aed;
  --border: #334155;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
}

body {
  background: var(--bg-dark);
  color: var(--text-light);
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
}

header {
  color: var(--text-light);
  text-align: center;
  padding: 0.5rem 0;
}
header h1 {
  font-size: 1.5rem;
  font-weight: 500;
  letter-spacing: 1.25px;
}
header p {
  font-size: 1rem;
  font-weight: 400;
  color: var(--text-subtle);
  margin-top: 0.25rem;
}

main {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  justify-content: center;
  align-items: center;
}

#buttons {
  display: flex;
  gap: 1rem;
}

button {
  padding: 0.25rem 0.75rem;
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: 12px;
  cursor: pointer;
  background: #888;
  color: #ddd;
}
button.active {
  background: var(--accent);
  color: var(--bg-dark);
}
button:hover {
  background: var(--accent-hover);
}

footer {
  margin-top: auto;
  margin-bottom: 0.5rem;
  font-size: 0.85rem;
  color: var(--text-subtle);
}
footer a {
  color: var(--text-subtle);
}

#game {
  user-select: none;
  display: grid;
  grid-template-columns: repeat(var(--grid-size), var(--cell-size));
  grid-template-rows: repeat(var(--grid-size), var(--cell-size));
  background-color: var(--card-dark);
  gap: var(--cell-gap);
  border: 3px solid var(--border);
  border-radius: 1vmin;
  padding: var(--cell-gap);
  position: relative;
}

.cell {
  background-color: var(--bg-dark);
  border-radius: 1vmin;
}

.tile {
  cursor: pointer;
  position: absolute;
  display: flex;
  justify-content: center;
  align-items: center;
  width: var(--cell-size);
  height: var(--cell-size);
  border-radius: 1vmin;
  font-weight: bold;
  font-size: 3.5vmin;
  color: #111111;
  background-color: var(--tile-bg);
  left: calc(var(--x) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
  top: calc(var(--y) * (var(--cell-size) + var(--cell-gap)) + var(--cell-gap));
  animation: show 200ms ease-in-out;
  transition: 100ms ease-in-out;
}

@keyframes show {
  0% {
    opacity: 0.5;
    transform: scale(0);
  }
}