When designing traditional pixel-art games (in general and in GameMaker specifically), it is generally desirable to keep your camera pixel-perfect to avoid rotated pixels and reduce various other artifacts:

This, of course, comes with an unfortunate caveat: it can be very hard to make your camera movement look good - especially if small speeds and/or acceleration/deceleration are involved:

This is a demonstration of an approach that allows you to escape this problem - by making the camera 1px wider and taller and having it draw to a surface, we are able to then offset this surface to make up for fractions in the camera coordinates:

An alternate approach involves drawing a half-pixel (at the game's internal resolution) frame at the edges of the screen so that you can wiggle the game's default surface (application_surface) under it without making it apparent to the player.

• Example by YellowAfterlife
• Tileset and background taken from "Pixel Adventure" by Pixel Frog
• Inspired by Hyper Light Drifter camera
  (which likely uses the "alternate approach" described here)