Hi, I want a cat tree but they are all either too expensive or too flimsy... ...SO. I have decided I may build one. Over the last few months I've bought some stuff, like a few different kinds/forms of sisal, including rope and sisal carpet remnants, and most recently some fleece blankets from a thrift store. My biggest problem is figuring out a sturdy enough base and how to make the levels. We have some fallen trees in the yard I think will work for a thick and sturdy base but the levels are different. Is it possible to bend wood or are the premade ones a certain type?? Thinking those circles may be too difficult to make and I could make a square one with some leftover plywood? She may like the round ones though. Anyways, help? Is this even possible or is it just a dumb idea? TIA.