This HUD clock from [Kiwi Bushwalker] is one such example. The build relies on four 8×8 LED matrixes to display the four digits that make up the time, run by the MAX7219 driver chip. However ...

making the clock nearly transparent when in use and fully transparent while turned off. It integrates the 24-second, timeout, and game clocks in one piece of hardware – a first for the league.