:root {
  --cell-size: 100px;
  --mark-size: calc(var(--cell-size) * 0.8);
}

body {
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background: #1a1a1a;
  font-family: Arial, sans-serif;
  color: #fff;
}

.container {
  text-align: center;
}

h1 {
  color: #4CAF50;
  margin-bottom: 2rem;
}

.game-info {
  margin-bottom: 2rem;
}

.board {
  display: grid;
  grid-template-columns: repeat(3, auto);
  gap: 10px;
  margin: 2rem auto;
  width: fit-content;
  background: #333;
  padding: 10px;
  border-radius: 10px;
}

.cell {
  width: var(--cell-size);
  height: var(--cell-size);
  background: #222;
  border-radius: 5px;
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  cursor: pointer;
  transition: background-color 0.3s;
}

.cell:hover {
  background: #2a2a2a;
}

.cell.x::before,
.cell.x::after {
  content: '';
  position: absolute;
  width: calc(var(--mark-size) * 0.15);
  height: var(--mark-size);
  background: #ff4444;
  border-radius: 10px;
}

.cell.x::before {
  transform: rotate(45deg);
}

.cell.x::after {
  transform: rotate(-45deg);
}

.cell.o::before {
  content: '';
  position: absolute;
  width: var(--mark-size);
  height: var(--mark-size);
  border-radius: 50%;
  border: calc(var(--mark-size) * 0.15) solid #4CAF50;
}

.cell.win {
  background: rgba(76, 175, 80, 0.3);
}

button {
  padding: 1rem 2rem;
  font-size: 1.2rem;
  background: #4CAF50;
  border: none;
  border-radius: 5px;
  color: white;
  cursor: pointer;
  transition: background-color 0.3s;
}

button:hover {
  background: #45a049;
}