Pretty fun and not too challenging, got to level 9 before I stopped.
One thing I really disliked is how the UI zoomed in when you speed up. That kind of made it hard to keep track of the enemies on the radar.
Also, on my first go I flew around a bit, couldn't find an enemy, crashed into one by accident, then moved to level 2, flew around some more and couldn't find any enemies at all. Perhaps the playable area should've been restricted/wrap around the map. You could also add arrows on the edges of the screen pointing at enemies. Either of those things would've made it easier to find the enemies if you move away from your starting location :)
Pretty cool idea, I enjoyed it :)