Xalaxer

Xalaxer is an 8-bit vertically scrolling shoot-'em-up with a twist. Instead of simply blasting his way through the enemy fleet with one spaceship, the player controls two spaceships simultaneously. Both ships are located at the bottom of the screen, and can only move left or right. The blue ship is controlled with the A and D keys, while the green one - with the mouse. Shooting is automatic. The player needs to destroy as many alien ships as possible without letting too many of them reach the bottom of the screen, otherwise it's Game Over. After one attempt a Left Hand or Right Hand mode is unlocked that allows to play controlling only one ship.

The name of the game is obviously derived from 8-bit classics like Galaxian, Xevious and such.