This was a past game that I was working on. Now I'm making anew version of this concept in which you don't draw, it just doesn't work with game-play, and wouldn't make a good puzzle, sorry if you wanted to be able to draw, but that's for another person to make.
Sketch is unfinished, but im pretty happy with it so... here it is! (Please tell me if you like it, if it has any problems, ideas, etc.) The top variable it lead and bottom is extra lead. Oh and, in case you're wondering, NO, I WILL NOT ALLOW UNLIMITED LEAD.