Not bad at all
I found it to be a game that's not too hard or too easy. Although the collision detection could use some work. To be precise, when I'm walking off a ledge and onto a beetle, it'll detect it as the beetle is hitting me, when in any traditional Mario game, it'd be a hit for him. Also, I find that if I'm not firmly placed right in the middle of a small platform I'll slip off, which can be a bit of a pain. Nonetheless, great job.