Viability: I think the game is fun and cute. I think you are on to something very good here. There are some systems I would add are a timed damage mechanic (grace period) so the health doesn't get hit again right away. I would also add a bounce material to the enemy so it sends you away.
Presentation: I like the use of music the cute background art, and even though there is no explanation at the start, the objective is still clear.
Theme: Feels like a relaxing and casual platforming game. Fun and simple. Getting some Kid Icarus vibes!
Engagement: I really want to get to the top of this games map! I think you should add more over time, but, right now I like some of the fun platforming mechanics!