I'll agree that it was a good idea, and I liked that the levels changed each time I played. The sound was pretty solid as well. I think it was a good attempt. That said, it sounds like you want some honest feedback, so I will give a little.
I think the two main complaints I could raise might be around player/enemy movement. Not having the player sprite face a direction (or having some other indicator) made it hard to tell where my attack was going to go. I can remember what direction I last walked in, but it's a little unexpected to not have that visual aid. Additionally, it feels weird that enemies don't stop moving/slow down/change direction/do something when they're hit.
Please don't be discouraged; as I said, I still think it is a good entry.
As a last note, the theme is present, though maybe a little subtle. The plant growth links the levels together.