This is a complete 4-bit adder. It is a machine that will take two 4 digit binary numbers and add them together. It uses simplified versions of my logic gates that are powered by gravity.

Here`s how to work it:

At the top of the machine you`ll see A + B = S. A and B are the numbers you need to set so the adder can find their sum.

Just below the equation you`ll see places to input values for A and B. You use the black and white circles on the orange platforms as input.

Black ball/circle = 1 = true

White ball/circle = 0 = false

Set A or B to a value by putting either a black or white ball in their 8, 4, 2, or 1 slots. The sum of the slot values that black balls are in is the decimal value of your input.

For example, if you wanted to set A to 5:

Put a white circle in slot 8.

Put a black circle in slot 4.

Put a white circle in slot 2.

Put a black circle in slot 1.

The sum of the slot values where black circles are set is 4 + 1 or 5.

The machine will not work properly unless all eight slots have exactly one ball of either color in them.

After that you simply press play and watch it work (may take a while.)

The solution or sum S is at the very bottom of the scene. All of its slots should be filled with a black or white circle. To find the value of the sum add up all the slot values where black balls have landed.

Some possible bugs are:

Balls bouncing unexpectedly in the wrong place.

Balls hitting each other in places they need to cross paths.

Please do not rate this low if you do not understand how to use it. I tried to make the instructions very clear but I will gladly explain more if needed.

Hope you enjoy it!