(As written in the N in-game help)
Like happy little puppies, these robots will eagerly scamper along the ground towards you. Unlike most puppies, they'll kill you if they get close enough.
Floorchasers (also called floorguards) are generally stationary, harmless and cute – until you land on the floor they guard. Then they charge towards you with amazing speed... and kill you upon contact with an electrical discharge similar to that of the zap drone. Once you enter their line of sight (which is horizontal to their left and right, even through midair), they will move in your direction very quickly until they reach the end (either the end of the platform or the edge of a map). If you are still there, they move in the opposite direction... and so on. Fortunately, they are only able to move on horizontal surfaces, and not slopes and curves. Sometimes, like in 02-4: (Don't) go for the gold, they can move over horizontally placed doors which are used to bridge a gap between tiles. They do this even if the door is open. If there is a horizontal one way platform bridging a gap between tiles, however, they cannot pass along it.
Keep in mind that they are very fast, with speed slightly greater than the ninja at a full sprint. Therefore, you can't outrun them for long distances, so you'll need to jump before they touch you. When you can't jump (in unit-width areas for example), life becomes hard, like 45-3: Manimal Lust.
- 45-3: Manimal Lust
Also keep in mind that floorchasers can go through all types of doors. Here, unfortunately, doors cannot help you survive.