Let me start with saying that this game has frustrated me to no end at times with its difficulty and insta-death scenarios. Its a shoot'em'up kind of game in limited arenas of sorts and you beat the level once all enemies are dead and cleared out which you have to do under a fairly strict time limit. A lot of its design choices feel like the are taken or at least inspired by old arcade games since if you die and game over on the third out of four levels in a zone you will need to beat the first two again to retry that area....something that will infuriate you on the harder levels.
The game has a challenging mix of achievements for doing various specific tasks on specific levels or bosses making the game even harder then just playing it normally. Some of these will only take a try or two while others (specially "Sneeky Incursion" that took me 20+ tries) will test your patience and skill quite a bit.Time to 100%:
2-5 hours (depending on skill and luck)