This is a fantastic demo, and a few tweaks away from forming a killer game. The controls are about perfect. The ability to strafe was such a pleasant surprise. Levels are enormous for this platform. The intro overview shows that off, and provides guidance. 

The simplest change that would make the biggest impact is more color. There's colored elements in the background - you've obviously handled scrolling that in. Tinting whole rooms, or decorating them with similarly-colored objects, would make navigation more natural. It would improve the at-a-glance identifiability of the already-present variety.

Enemies, same story. They have a great range of behaviors. The cliche of palette-swapping to show which thing they do is cliche for a reason. Having to guess whether a turret is going to fire diagonally, or even come at you, is holding back the combat, when movement and shooting are this tight.

This is impressive! Music sort of reminds me of DOOM. But I get just a black screen if I do a warm reboot, that might be worth checking on.

A pretty interesting Alien Breed clone game. Congrats !

Impressive to see scrolling in all directions and 8-way movement! I like the ability to strafe. The shaking of the screen when hit by an enemy is a nice touch! I enjoyed the music, but it would be nice to have more sound effects. The meanings of the HUD elements weren't immediately obvious to me, and they are a little hard to see sometimes.

Overall - nice work!

Free scrolling and 8-way motion on the player avatar--impressive for a NES jam!