Very nice game absolutely nails the retro look! Gameplay as the minute flaw that some enemies sometimes throw projectiles through walls but nothing game breaking, just adds to that retro feel.
9.5/10 would play again.
A little side note: when I'm doing retro styled games I like to let the camera render to a render texture and display said texture. You can then scale the resolution of the render texture. This way you can render your game in, for example 420*270, and display it on a full HD monitor without issue and ofcourse you can set the filter mode to any one you like/think fits your game best