* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background: #0b1020;
  font-family: Arial, sans-serif;
  color: #e5e7eb;
  padding: 20px;
}
.game-container {
  width: 100%;
  max-width: 500px;
  background: rgba(255, 255, 255, 0.03);
  padding: 25px;
  border-radius: 20px;
  text-align: center;
  border: 1px solid rgba(255, 255, 255, 0.08);
}
h1 {
  margin-bottom: 18px;
}
.mode-select {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 15px;
}
button {
  padding: 14px 22px;
  border: none;
  border-radius: 12px;
  background: #3b82f6;
  color: white;
  cursor: pointer;
  font-weight: bold;
  font-size: 14px;
  transition: 0.25s;
}
button:hover {
  box-shadow: 0 0 12px rgba(59, 130, 246, 0.35);
  transform: translateY(-2px);
}
#status {
  margin: 15px 0;
  font-size: 18px;
}
.board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 12px;
  width: 100%;
  max-width: 350px;
  margin: 20px auto;
}
.cell {
  width: 100%;
  aspect-ratio: 1/1;
  background: #111827;
  border: 2px solid #334155;
  border-radius: 14px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 52px;
  cursor: pointer;
  transition: 0.2s;
}
.cell:hover {
  background: #1e293b;
}
.restart-btn {
  width: 100%;
}