Update:
I had display brightness set to adaptive. I left it set to adaptive, but turned brightness right down, and battery seems to last longer now, and a fair bit less heat is generated.
I was playing indoors (edit: before and now), so there was no good reason for it to be very bright. Maybe the game is confusing the settings? Needs some testing before this becomes more or less than just guesses.
The battery is still drained quite quickly, but i have been able to play quite a lot now, so maybe this will help someone.
I guess great games need a great amount of energy to run. Seriously, I play this game so much that it is 90% of my battery usage.
