I haven't seen warnings just yet, also the brightness is at 20%
Hopefully it's the game, since the game is graphic-intensive. Other games don't heat up the device that much(just gets a tad bit warm).
Play jurassic world regularly and I can only say it gets a little toasty when I play it whilst it's still on charge. Don't notice any drastic heat changes or anything that would get me worried. Got a spigen case around mine.
Yeah it seems with most modern devices heat kind of comes as part of the package with them being very slim and packed with tech. Wouldn't say it's anything to worry about though dude