Metal Slug fans know how it goes. You hold down on the D-Pad and run, killing everything that shows up in between the left side of the level and the right. Weapon upgrades are picked up. Vehicles are driven. Bosses are killed. It's the Contra formula, and has, for many years, proven itself to be completely capable of delivering a good time. Metal Slug XX does very, very little to change this. In fact, it is this, being a port of the Nintendo DS release of Metal Slug 7 released a few years back. What it does differently is add in local cooperative play, something mysteriously absent from the DS edition. Beyond that, though it's par for the course, something which may find itself isolating gamers who haven't familiarized themselves with the series in the past.