I haven't built any electronic gizmos like this in 10 years. I don't know what possessed me to make this, other than binary is geeky and blinking LEDs are cool.
It's strangely transfixing to watch it count.
The "brain" is a 74HC590 8-bit counter. The clock is provided by the 555 circuit in the corner of the board.
Currently displaying the number 245. It takes approximately one minute to overflow.