Apple :: MBP 13"cooling Temps

I know that the mbp can get hot when doing some heavy computing, however I was playing a simple online game the other night called plants VS zombies, check it out if you don't know it. Anyways after playing for only a few minutes I noticed that my macbook was getting very warm, and after about 15 minutes of playing it the underside of it was hot to the touch and the topside(keyboard) part of it was quite warm and I could feel the heat radiating off of it. I haven't even had it for a week yet but have done quite a few things including watching movies both on a HD and from a DVD. I have had multiple browser sessions open with wireless on music playing in I itunes etc. And I have played around with some other settings etc. Nothing else I have done on the computer has made any part of it warm to the touch, but this simple online game made it to hot to sit on my lap, and very hot to the touch and has me worried something might be wrong with it, I would hate to play a more demanding game, or do some video editing etc..which is one of the reasons I bought this computer over a PC in the first place. I still have 10 days or so to return it for a full refund or else exchange it for another I have tried restarting the system a few times and playing the game again and the temps shot right up again.