Algodoo

This thing is cool. Really cool. Perhaps even mind-bogglingly cool, depending on how easily your mind is boggled.

This machine operates in binary numbers. It can add two eight bit numbers together, to get up to a nine bit sum. For each `bit` (tabbed circle) a red rectangle at the top means 0, and a black rectangle at the top means 1.

To operate:

hold A until the first desired binary value is displayed on the top row of bits. Hold B until the second desired binary value is displayed on the lower row of bits. Then, press enter to calculate the sum of the two, which is displayed on the lower row of bits.