Xain D Sleena is an excellent platformer remake by X-Out, developer of the equally impressive Prototype. You assume the role of a soldier with a mission to save each of the five planets invaded by the enemy forces.
Each location consists of two equal parts. You have to fight your way to the enemy base station, detonate it and leave on your ship. The escape is basically a horizontal shooter stage with a boss in the last planet.
Plenty of options to tweak such as autofire, difficulty and image quality. Having to restart from a save point after losing all health may discourage a few players from playing much but fans of the original will cherish this remake.
Try setting Quality = 0 or Filter = 0 in the engine.cfg file if the game doesn't work at first.