Suppose both A and B have 1s in the current location. |
The glider in the A stream kills the glider in the top glider gun stream, so the top glider gun stream transmits a 0 to B. |
The glider in the B stream passes through the hole in the top glider gun stream, and is eaten. |
Meanwhile, the hole in the top glider gun stream continues on to the left glider gun stream. |
The glider in that stream passes through the hole in the top glider gun stream, contributes a 1 to the current location of A or B. |
That is, if A and B both are 1, so is A or B. |
Return to the or operation.