Super fun game! It felt super satisfying to spray these hordes of alien cockroaches hehe. Gave me a DOOM feeling.
For improvement I would say the movement mechanic is really quirky, I'm not sure if it's on purpose but it's possible to use the ramp and jump to the alien spawn and then struggle to get back.
Also a reload animation would have been great, and maybe I didn't get there but are there other weapons except the m16?
And lastly I think a bit more challenge from the starting waves would have been a good addition.