Briefly, in case you've never played MasterMind before, there's a hidden sequence of 4 colours that you have to guess (well, intelligently discover!). After entering a 4-colour sequence in the bottom row you'll be given a mark consisting of black & white pegs. A black peg indicates that you've placed a correct colour in the correct position (it's up to you to work out which one); a white peg indicates that you've chosen a correct colour but not positioned it correctly. Therefore, for example, if your mark is 4 white pegs, you've chosen the correct colours but they're all in the wrong positions. Have another try in the next row up until you get a mark of four black pegs (and a 'Well Done!' at the top of the applet). Clearly the object is to discover the hidden sequence in as few attempts as you can.