html, body {
  height: 100%;
  width: 100%;
  margin: 0;
  padding: 0;
  background: #111;
}

#centerWrap {
  width: 100vw;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

#gameContainer {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center; /* Center children horizontally */
  justify-content: center; /* Center children vertically */
  background: rgba(10,10,10,0.98);
  border-radius: 2vw;
  box-shadow: 0 0 30px #0008;
  padding: 40px 0;
  min-width: 800px;
  min-height: 700px;
}

#fullscreenBtn {
  position: absolute;
  top: 60px;
  left: 20px;
  z-index: 10;
  background: none;
  border: none;
  color: #836EF9;
  font-size: 2.2rem;
  cursor: pointer;
  opacity: 0.8;
  transition: opacity 0.2s;
}
#fullscreenBtn:hover {
  opacity: 1;
}

canvas {
  display: block;
  background: transparent;
}