Very fun game. The cooldown after every shot makes you really feel the pressure. There are some things that could be added like boundaries so the player can't go out of the screen, diversity on the enemies so the gameplay it's a bit more unpredictable, or abilities/powerups so the player can escape from multiple enemies. 

Had fun trying to survive for as long as possible. Maybe put in a timer to add waves with enemies after a certain time. Giving the player ammunition and forcing them to reload could be an interesting way to add some decision making into the game.  Which could also be small dots that you pick up for a power-up. 

When you move in the same direction as you shoot it kinda glitches out a little bit, and the delay between shooting and the projectile being shot is a little too long. It was satisfying to play though! 

there are no boundaries so I kind of cheesed it by continuously going one direction lol.