Weighing balls solution

This puzzle is described here. A summary: you have twelve balls, eleven the same weight and one different. You are allowed to weigh them against each other in whatever combination you like, three times. Find the odd ball, and whether it is lighter or heavier than the others. There is a further discussion of the solution here, but I suggest that you try out the demonstration below for several choices of odd ball and weight first, as it is easier to understand.

Choose a ball to be the odd one out, and choose whether it is heavier or lighter. The computer promises not to peek! If you prefer, you can chose random so you don't know yourself. The computer will then describe the weighing to do, and explain what the result is. It will also discuss the implications of each result. When describing the result, it uses > (greater than) which means that the balls on the left are heavier than the balls on the right. It also uses < (less than) which means that the balls on the left are lighter than the balls on the right.