Hi there. Sorry to hear you didn't enjoy the game. Could you please specify which parts you didn't like? Also, Sand Dollars are real shell-like objects found in the ocean. You should look it up. Also, I've just started using this game engine (Unity), so I'm not great at it yet. :P
Yeah, this game is definitely more on the short side. I'd like to add more playable characters + levels in the next entry :P Thanks for the feedback :)
Oh, and the reason I don't make actual Mario games here is because it's technically illegal outside of sites like Scratch. Scratch is purely educational so using copyright material is allowed there (unless a DMCA is filed).