Hi there.

As you yourself mention, the phone is obviously being stressed from the graphics requirement, and thus overheats eventually. Don't think there is much to discuss on that .

But, maybe a tip can help. Do you hold the phone in your palm while you game? Maybe you should try putting the phone on the table, lying on top of a pouch or something while playing. Maybe the heat from your hands are the "tipping weight" for the phone to overheat .

At least worth a shot I recon. Hope it helps

 

Just play the 20 levels, then give the phone a rest