A few people have asked for more information on the cat tower, so I'm posting some of my designs and plans, plus a close up of the project. If you're thinking of making your own, here are a few things to keep in mind:
1. I curved the front plywood in order to reduce wall space without reducing volume. If you have the space, I recommend leaving the front FLAT, especially if you're a beginner or even intermediate worker with construction. There's absolutely no reason you can't just design a simple box shape for this! Be creative! The size and shape are largely meant to benefit YOUR living space.
2. Using a right angle corner with a curved hypotenuse, my 10 lb cat fits through a 7" hole (measuring along one flat edge). My 17 lb cat needs a minimum of 8", but 9" to be comfortable. Use a cardboard box and start by cutting a 7" hole in a top corner and putting the box over your cat. If they can jump through the top pretty well, widen it another inch. Do that until the cat can jump through without touching the sides. The farther apart your floors are, the wider the hole needs to be.
3. The front "window" holes don't all need to line up. That's just what fit with my design. I'm currently working on one for my parents' cats, and it's much more organic with holes in different spots. Pick one to suit your own style.
4. Take into account what your cat likes to do normally. JoJo LOVES being up as high as she can, so I built this thing REALLY tall! Chewy likes a nice, dark, cozy spot to just sit in, so I built the bottom floor a little larger for him to feel comfortable. The result? JoJo plays on the top level all day and Chewy chills out at the bottom. The outside design is for you, but the inside is for them.
5. Support, support, support! You cannot be too careful adding support. Support along all the sides, extra weight on the bottom, and put support brackets under each level. Screw some carpeted levelers into the bottom if you have wood floors. Plastic levelers if you have carpeted floors.
6. I kept mine entirely enclosed, but I left one of the back panels as removable for easier cleaning.
7. Old carpet squares can be easily cut to fit the interior levels. I bought 5 squares at Habitat Restore for $15 (only used 4). I ran some extra strips of carpet along the walls between levels. It helps the cats get a good grip to climb between floors, but is also just a very excellent scratching post hidden away!
Feel free to ask me if you have any questions while making yours! It's a lot of trial-and-error, so have fun with it!