If you feel sorry for the Koopas in Mario, might I suggest Daisy's Garden? Daisy must find a way around enemies and other obstructions without killing them. The readme, if I remember correctly, even said the game was meant to be a nen-violent alternative to Super Mario! https://archive.org/details/DaisysGarden_1020 More of a side-view puzzle game than a platformer; in fact Dasiy can't jump at all.
Yeah, the domain was brought back a while ago, but I don't really understand what's the point if the site won't be updated. It's basically just spending money on hosting fees for something that was abandoned already. Well, it's their money I guess. ^_^
Thanks! ^_^