Here are the things I learned while watching Ninja Assassin[1]:

1) Human bodies are basically overpressurized bags of blood that will explode at the slightest provocation.
2) Europe has a severe ninja infestation.
3) Ninjas are like cockroaches: for every one you see, there are at least a dozen you don’t.
4) Ninjas are like cockroaches: they really hate it when you shine lights on them.
5) Ninjas will kill anyone, as long as you pay them with one hundred pounds of gold.
6) Ninja stars[3] are every bit as cool as you thought they were when you were eight.

[1] There really was way too much plot getting in the way of my chopsocky, at least for the first third of the movie. But, okay, a ninja with a troubled past[2] and a precocious (let’s say) Interpol analyst team up against ninja hit squads and the police, on a quest for bloody revenge.
[2] I mean, more troubled than that; like, take ninja as the troubled baseline, and then adjust from there.
[3] No, not shuriken. These were definitely ninja stars.