Very good game, I love that buttons are part of the game. I like how everything is physics based and very intuitive.
At first I didn't notice the explaition in the background, so maybe it could pop out a bit more. (At least for the first order)
Also the bike tends to fly away when you bring other parts nearby, perhaps the parts could snap or bike could move less when it is attached.
Overall, a very good, fun and well made game,