Overall, it was okay.
The controls were very smooth and felt good, which is the most important thing.
After 30 enemies, I ran behind the stone wall (top left and bottom left sides) because I wanted to see if there was more to go, but then I couldn't get back out and lost.
I wish the enemies had dropped packages with ammo and food. That would have made it more exciting. A larger area to move around in would also be great.
The graphics were okay overall. I didn't understand the black hole on the left. It would have been enough if the enemies had spawned at the edge and you could see that.
The sound effects were good.
If you need any more feedback, just ask. I'll try to answer your questions :)