I have been looking into 100% pen projects, and they are pretty cool, so I'm going to try making some of those. This is just a test of a reverse snowfall that is made by 100% pen. I had trouble making this because there were no 100% pen tutorials, but you don't have to go through that trouble because I will explain the concept
So this works by storing the data of everything in lists and variables. In a really fast loop, a sprite goes to specific coordinates and does "pen down" "pen up". This leaves a mark. The next frame, it resets everything and marks the screen again, only the coordinates have changed.