I second TaftPunk's recommendation to have a reset button of sorts so you can iterate and test your contraptions.
The concept is really cool and I'd love to see what you can do with it :). If I may throw out a suggestion (based on my personal preferences so take it with a grain of salt). I really love games that give vague instructions/clues to how a contraption works. Because then part of the fun is discovering the pieces to begin with. It would be really interesting if the help menu/tutorial was actually more like a alchemist's notebook that you can flip through that has diagrams and things which hint at how things work without actually telling you anything :O. Kinda like Myst if you've ever played that.
Lastly, the ui didn't fit to my screen size properly so some of the help menu text wasn't visible (went off screen) :(. Though I was able to figure out the objective and completed the game (although I did so while the game was paused... couldn't get a contraption to do it for me unfortunately :P).