It's called N, you can play it online
here .
Might take a few goes to get used to the general movement, but after that it's the sort of which is good at getting more challenging the better you get.
There's a standalone version you can download for free to play when you aren't on line from..
http://www.harveycartel.org/metanet/downloads.htmlThink it might be slightly updated from the online version too.