Hey CGB Games, good game!
Just like to point out the glitch that happens after death, the space bar still dashes the character. Here are some more improvements:
Add like a effect to the missiles hitting the alien(explosion or damage)
Add a proper game over scene(like Game over, with the screen going dim , and large buttons)- A back story cut scene? Like the origin of the alien and what's it purpose
- Objective bar on the UI , showing what the user should do.
Overall good start, but you can get even better by some more changes and hard work! I hope this makes your game even better.