Worked lately on a level editor. It goes pretty well.
As with all of the menus, you can use it with just the keyboard (potentially gamepad later on, too!) or mouse.
Levels are packed into levelpacks, so you create the whole story as a whole.
Next to do:
* (back/fore)ground scenery
* layers for scenery (main game objects can't really be layered, as they have to be drawn in proper order)
* trigger/event system for levels OR scripting; the idea is to make it flexible enough to be able to create even the tutorial levels just in the editor, without any extra code.