html, body {
  height: 100%;
  margin: 0;
  padding: 0;
  background: #000;
  overflow: hidden;
}

#game-container {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  width: 100vw;
  height: 100vh;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background: #000;
}

#gameCanvas {
  display: block;
  width: 100vw;
  height: 100vh;
  background: #000;
}

#score {
  position: absolute;
  top: 10px;
  left: 10px;
  color: #fff;
  font-size: 20px;
  z-index: 10;
}
#startBtn {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  padding: 10px 30px;
  font-size: 20px;
  display: none;
  z-index: 10;
}