A ring counter is a type of counter composed of FLIP-FLOPS connected into a shift register, with the output of the last flip-flop fed to the input of the first, making a "circular" or "ring" structure.

There are two types of ring counters:

1. A straight ring counter, also known as a one-hot counter, connects the output of the last shift register to the first shift register input and circulates a single one (or zero) bit around the ring.
2. A twisted ring counter, also called switch-tail ring counter, walking ring counter, Johnson counter, or mpnius counter, connects the complement of the output of the last shift register to the input of the first register and circulates a stream of ones followed by zeros around the ring.

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Charest's clock is impressive due to the physical layout, thanks for pointing it out. It would make a kid vow to take up engineering. Nixies would be the ideal display except that they are so expensive. Alternatively maybe a ring layout simulating an analogue clock.

I think that a discrete clock was what triggered my passion for electronics as a kid.