In Factory Balls Forever, you start with a blank ball. The game will show you a target ball that you need to create. You can use different tools on the screen, like paintbrushes to change the ball's color, and stickers to add patterns. You perform a series of operations on the ball in sequence to gradually make it look like the target ball. Once you think you've achieved the correct appearance, you can submit your result. If it matches the target, you pass the level and move on to the next one.