Here's the idea that had I struck upon it a few weeks ago, I would've thrown together for that "You Are the Villain" Ludum Dare. It's been a while since I've done one of these, and it's a bit early for this weekend, but here we go!
It's a riff on the end of Super Mario Bros. 3 in which you are a big turtle-y boss who has to crush the heroes who are trying to break into your castle. Crush them when they're on the bridge, but don't fall in, and don't let them slay you!
Press X to jump. You can move in midair with arrow keys.
Nine stages in all!
(It's maybe a little buggy. Just a little.)