The game is pretty cool.
It has a very cartoon superhero feel to it.
Diverse opponents will engage you in various ways with a good variety of attack styles and are often over the top. Some of the more sophisticated opponents will require you to find their weak spots and aren't simply "shoot it to death" affairs.
Your character looks pretty slick in his costume and has good moving and shooting animation. He also has a very very cool parachute feature that allows him to glide. Both the animation and the feel of it are very good and by the end of the game, I still wasn't tired of it.
Mouse-using shooter purists might be disappointed at the lack of precise aiming (your gun works like a machine gun and there is no vertical aiming... the vertical axis is auto-aim), but that setup works well with the action as you'll be moving and jumping all the time to dodge various attacks and also to access different parts of the levels while fighting. Also, there is an sniper feature that works like you'd expect a sniper riffle to (except that you can shoot explosive rounds when you find some!) and for some parts of the game, you have to use it so purists won't feel like they are completely left out.
The puzzles are pretty ingenuous without being frustrating (you'll have to stop and think, but if you look around, you should get it) and while the environment isn't destructive per say, there are many scripted environment changes that are pretty cool and dramatic.
Part platformer, the game makes good use of the vertical axis to navigate across the levels and will make sure you need to use that cool gliding feature on various parts of the levels to move on (or to avoid hurting yourself when you fall from great heights). Also, the gliding feature makes it more user-friendly as a platformer, because you'll be able to use the glide to correct your fall.
The graphics are somewhat dated, but they do an adequate job at portraying the alien vessel-asteroids (a lot of earthly-metallic colors) and the architecture the levels will look refreshingly weird and alien. Level design in this game is top notch and never plain or boring.
With all this praise, I should mention the few bad parts of the game.
The game is fairly short. I did not play with a chronometer, but I'd say I finished the game in 8 to 12 hours.
Also, while you can save between levels, you can't save during the levels. However, this isn't as bad as you'd think as the levels are fairly short and you should complete them in 1 to 3 attempts unless you are new to shooters or platformers.
Furthermore, I found the initial key setup unintuitive (in particular, the ability of the mouse to move you forward or backward instead of just sideways) and if you are anything like me, you'll have to adjust it to make the game enjoyable. Given the number of games I played lately that got the initial key setup right, this issue stuck up for me.
And finally, there is a music video at the end of the game that is just weird. Its in French and frankly, you are better off if you don't understand it, because the lyrics are nothing to write home about.
Overall, the complaints are minor and the greatness of the game greatly overshadows its weaknesses, hence the 5 stars.