How to...

Click to select a peg
Click on peg hole to place peg
To de-select a peg, click on it a second time
You may remove pegs by clicking on them and clicking on corresponding color in the peg tray
After forming a guess with 4 pegs, click on "Guess" button to see the results

Two player game: While Player 2 looks away, Player 1 will place four pegs in Code Tray and then click "Cover Button"