Yeah it's just about scores - like a non-button-smashing action game where you get fun if you're a creative player. Apparently the "melee attacks stronger than bullets" (now from the enemy side) rule is true in this game.
There are five difficulties: VE, Easy, Normal, Hard and Very Hard. Also the achivement list sucks or it's just really weird.
The demo is on Easy, no wonder why the enemies were are all dumb like Krall.