I spent about 2 hours (ish) working with the level editor on SMBX to produce this small and somewhat entertaining level (but most of that time was spent learning how to use it. I've just installed the game today.). When I say small, I mean... like... pretty short, though. So go ahead and try it if you feel like it; I'd appreciate some general constructive criticism to better my level designs in the future.
So I have a screenshot... And the file is below, enjoy my mediocre level


EDIT: I appreciate the review, it's very helpful, and I may make levels in the future, as long as my free-time permits.