#game {
  position: relative; /* メッセージを重ねるため */
}

#game-message {
  position: absolute;
  top: 50%;
  left: 50%;width:200px;
  transform: translate(-50%, -50%);
  font-family: "MS Mincho", "ＭＳ 明朝", serif;
 
  
  text-align: center;
  user-select: none;
  
  z-index: 1000;
}

#game-message.hidden {
  display: none;
}