Microbot

Go into challenge mode, choose a chapter, and complete 3 stages based on that chapter's theme.

For the most part you can just try to dash to the end by taking glimpses of your map and moving to the white marker that's the opening to the next room, though on occasion a door will shut in your way and you'll have to fight your way to some switches. The stages are generally fairly short, though you only have one life, so make sure to keep an eye on your bar and stop for gold atoms to refill when you're starting to get low.

Doing this in co-op with another person will make things much easier, since if either player makes it to the exit both get credit for clearing the stage (and of course, more guns.) Finishing the game and maxing out your favorite weapons before going for this will obviously make it that much easier as well: personally I found 4 Particle Cannons with 2 Hydraulic Acids on the back to be a good setup; Virus and Hydro-Nuke are great aux weapons to keep enemies off of you / dead, though if you're going it solo the speed boost may be handy as well.