Not Bad
Very nice for a first game. Clean and simple, although rather unoriginal. Very nice animations and also very smooth and professional.
Several improvements would be:
1. Wall-bouncing: doing so makes it possible to move faster than you intented. consider a pac-man style warp between sides or a less bouncy (or even damaging) walls.
2. Enemy variation, obviously
3. Feels a bit sluggish. I'd play with the speed. It could be a genuinely challenging game if you sped it up enough and made the right enemy spawn changes while still being very simple.
Keep up the nice work!