I'm in the process of making a shop in my town, where it uses hoppers and dispensers. I need a redstoner to set up this shop. In this shop, I need a system where you toss a certain item in the hopper, and the item you are purchasing comes out of the dispenser. But, I need this to be foolproof, so people can't just toss random crap in Sort of like the Bluewater Casino but not chance. I want it to be so that you toss a single item required in the hopper and it will always pop out the item they purchased, and if random crap is thrown in, it will be removed. If a builder of the Bluewater Casino could help build this that would be very helpful, since I know they are experienced with this sort of thing. Please post your application for this job in the comments! Thank you!