stage is certainly a weirder one, that's more of a hybrid of like... stage of a caterpie to a butterfree (yes i went there) and a physical stage. in the next advancement there will be a new place to stand on - a new floor.
it's a stretch though, that one.
edit: but level doesn't run into that problem. easiest example is something like a parking lot - a level can have stairs go between it just fine, or be called 2A, 2B, etc. in real-life there's a pretty similar way to do it.
--
The King Wang.
Listen up Urinal Cake. I already have something that tells me if I'm too drunk when I pee on it: My friends. - Colbert.