My iPhone 13 Pro is heating up during gaming

Hi there,

Recently purchased my 13 Pro and I am a regular gamer. But I've noticed after about an hour of continuous gaming on PUBG my phone heats up badly and the brightness decreases as result. It dims quite a lot. This phone does support 90fps and it's what's I'm using on the game so this doesn't make sense. Given the price and specs of the phone this shouldn't be happening. Any suggestions?