I don't think it's cruel at all to leave a cat indoors. My bengal is coming on the 23rd and he's going to be living in my room (which is seperated from my house). My room is about 14 feet by 16 feet. I'm buying him a very big cat condo, and building him a cat run (so he can get the outdoor feel *safely*. I have already bought him a BUNCH of toys, and will be interacting with him all day. I'm going to take him out on walks daily, sometimes around the block, sometimes to a park, maybe to a botanical garden so he can see other animals. The main thing is neglegence. If you neglect a cat than of course it's cruel, but if you actually care for it and spend time with it, then there will probably be no problem at all.