Need help identifying a game!

In Games

I used to play a game with my friends on the NES but I cant remember what it was called. It was a sidescroller, everytime you would enter a room to the left or right it scrolled sideways, it had co-op, The enemies that i remember where alien things and they didnt walk but to move around they jumped, the only weapon you had was a gun, to get to a new level you had to find a teleport, most of the background that i saw looked as if it were in a space ship. On the game cartridge there was a picture that looked as if one of the aliens had cut thru the cover and was coming out. I have looked everywhere for this game on the internet but i have not found anything like it. Soe of the information may be wrong considering its been more than 5 years since i have played it. Thx for all the help you can give me.

The closest I can think of right off-hand would be Alien Syndrome.

EDIT: I can't remember if that was co-op or not, though.

Thats not it but i remembered in co-op it was split-screen, horizontal

Sounds like ''.

This screenshot is from the Atari 7800 version, but you can plainly see the split screen 2-player co-op stuff.

Dood thats it! Thx so much. Now to go find it in some store. Probley equally ahrd as it was to find it on the internet.