A 2-bit binary multiplier. Simply enter one blue input and one red input, run round the other side to the outputs and your answer will be there. For some reason multiplying 3x3 will return a value of 7 but all other possible combinations work fine. I made this multiplier from a circuit diagram off Wikipedia (included in screenshots). It is a very simple design so wiring it up was the difficult part. I've uploaded the schematic so feel free to download and take a look :)