This was a nice Mario homage. I liked the art style and music/sound design. I've never seen a side-scroller tower defense before.
The gameplay was confusing. I didn't realize the first level was a tutorial level, so my first playthrough I had no idea what was going on. My second playthrough, I ended up placing everything on the top level and then not realizing the people all came on the bottom. My third reset, I did better, but I had no idea what anything I was placing did. It would have been nice to see item descriptions.
Overall it was a very professional-looking game. I just found it difficult to play.