Due to the nature of the design of this phone (ie, 90% of the surface area being covered in inherently heat-insulating glass), heat is kind of unavoidable.
You should see how how it gets playing San Andreas lol.
Main: HTS One M8 stock rooted
Traded: LG Optimus G E970, 4.1.2
Loaned: HTC Inspire 4g, PACMAN
Auxiliary: HTC Incredible, tinyCM10.1
Auxiliary: Nook Color, MirageCM7