Interesting concept, I think some things you can improve is maybe allowing the turning of the player (and maybe the enemy) so you can shoot at them! Right now I have to be horizontal or vertical to the enemies and I feel like it would feel better without moving so much. This would indeed increase the complexity of the game but it would make it feel more smooth! Other than that, I think this game fits the limitation well (You are the cause of your own doom most of the time, lol) and good job!
Also unrelated to how the game was, on trying to open the application my anti-malware had blocked it so I had to have it as an exception (Not sure how to fix that).