Thunderflash

This game is awesome. 5 Missions in this, once you beat it you unlock boss Rush. They also have a Survival mode in this. You start with 10 credits. Each time you game over they give you 5 extra to start with up to 20 credits. There is save points in this game so you don't have to start the whole game over if you die. You continue with 20 credits where you left off. To get the extra ending in this game which is totally optional you have to beat the whole game in 1 sitting.