Pretty fun, I liked the music and sounds. Visuals are also good, those spider are hard to see and blend with the background, but I'm having Minecraft invisible spiders flashback, so I'm going to say it's intended.
I'm not sure, but I feel like you are not going as fast when you are going in a diagonal (pressing two buttons) as when you are going straight, so I ended up just going in large circles around the map. I got wreck by the giant spider on wave 5 I think, don't think I could escape, would I've loved a movement speed upgrade! Other than that, yeah, shield visuals, I could see the purple bar going down, but that's such a small part of the screen to focus on when so many things are coming your way.
I did like the variety of monsters and that you get larger version later on, pretty neat, might be a touch too big though, couldn't see a thing haha.