Before anything, you need to know how to unlock the level editor! There are ten main 2-part stages that you need to beat. After the tenth or eleventh stage (I don't remember which) you will unlock the level editor. From there, on the far right side of the room, there are three doors. You want to go to the one on the left with a grid above it. Press down in front of it and you will be in the level editor! If there is a lock in front of it instead, that means you have not beat enough stages to unlock the editor.

When you are building a level, there are a few things you need to remember.
1. You can move where you want to place something with the arrow keys.
2. You can place an object by pressing [ENTER]
3. You can swap between a list of items with [SPACE] and [CTRL]. This is the list of items in order:
Block, Entrance, Exit, Spike, Chain, Conveyor 1 (left), Conveyor 2 (right), Teleporter A, Teleporter B, Water Top, Water, Ice, Laser Shooter, Shrink Ray, Invis Block, Glue.
4. You can press backspace while hovering over an item to delete it.
5. You can only build in the build area. You can move blocks outside the area, but it will not work.
6. You can press R to reset the build area. It will also show the instructions again.

The game does not actually tell you how to play the level, or exit the editor. The way to play your level is to move the object you have to where it says Play and hit [ENTER]. You can do the same for the Back button to exit the editor, where you will be teleported out to the door. When you do, you will be teleported to your starting point. You cannot edit while playing your level, and there is no 10 second limit. You can exit the test area by killing yourself, or pressing [S] to suicide.

When you do, there will be the normal effect when you die or complete a level in the regular game, and then it becomes the editor instead.
There is currently no way to save your level, in the form of a text document or on the Steam workshop. I hope they do allow us to post our levels to the Steam workshop, and allow others to play them!

Well, thanks for reading my guide! I certainly hope you enjoyed it! I couldn't really write much, because there is not much in the game yet, but I am excited for the developers to work on the game more!