Heat

[COOCOpUcHoo]

I don't have one, that was just a scenario, it happened to my tree frogs.

[Hypnotic]

I'm not really worried about that, I have cork back and side panels, the heat spreads quite nicely among them, my temperature probe is attached to the corner between the mat and cable and touches the wall where they both cross, so that should be the hottest point and that reads 28.5 right now.
If your worried about burning, just hang the heatmat a few cm above the substrate, so the pacman can't directly touch it.