It’s a Nixie clock made without a microcontroller ... diodes, caps, and neon tubes. The design of this is covered in the creator’s webpage. This clock was inspired by a few circuits found ...

The core of this build are a few tiny NE-2 neon bulbs. These are the same ... The actual code to do this is running on a microcontroller, though, so that might get a pass. This is just a test ...