What kind of home depot wood is safe for animals?

I have 2 degus (squirell like animals) and i want to build them some levels in their cage with wood. I have a local home depot but not sure what kind of wood i should use? Any ideas? Any alternative ideas for levels that i can get at the local home depot?

Preferably an untreated hardwood like maple or birch but those are more expensive. Untreated aspen is safe. Untreated pine shouldn't be used but it's safer than cedar or any treated woods. Whatever you do, DO NOT get any cedar or anything that has been treated with anything (ie: pressure treated-which contains arsenic).

yea , you could build or find a couple of wood boxes to stack on each other, cut holes so they can run though them. screw them together so they don't fall over, while they are having so much fun. plywood would work too besides pine or fir.

Pine and cedar are unsafe for hamsters, so I would guess that they would be unsafe for a squirell-like animal, also.

The only thing I know is TO NOT USE CEDAR its very bad for small rodents.