There is not much I can add, beyond that I have manually browsed through the MobyGames scrolling shooter database (without success).
Indeed, the game is a vertical "shoot 'em up"/shooter with the option to play solo or two-players (first player is Red, second player is Blue, if I recall correctly).
Beyond that, the major feature I can remember are it's power ups. A single power up item, which changes from numbers 1 to 4, can be picked up to get a better weapon. For example, power up N°2 enabled you to fire wide flames quickly. If I recall correctly, powerup N°3 provided you with lasers that fired diagonally.
It is all I can remember for now, but the game is very valuable to me as it was one of the very first (I think the second) videogame I played as a child.