Algodoo

NOT, AND, OR, and XOR (exclusive or) logic gates.
Activated with black and white balls.
Have usage indicator.

Black = 1 : Purple mechanics
White = 0 : Yellow mechanics

They can be stacked and combined to make neat paths of logic. For example you could try making an OR gate out of four NOT and AND gates.

All the gates have an indicator that shows if they`ve been used or not, gates can only be used once. If the two ball input values on the AND, OR, and XOR gates are too close together the indicator may not operate properly but the logic should still work.

The TWO gate simply produces another one of whatever was put in it.

You`ll notice that there are two copies of each gate one with text and the other one just shows the mechanics.

The platform thing to the right of the TWO gate is for putting under two gates whose output will be fed into one gate. It helps make sure the balls enter at different times.