Alter Ego is an automatic side-scrolling twin-stick shooter. The left stick moves your avatar, while the right stick fires in the direction you push it. The basic premise is to get to the end and defeat the boss at the end. Along the way, you have to destroy purple bubbles that block your way, as well as avoid/destroy enemies, some of which will fire projectiles at you.
Alter Ego has a special element to it. There will be yellow bits scattered around the stages. Collect 5 and you will level up, which will increase your firepower. Get hit even once and your level will go down by one. The max level you can achieve is level 10.