If you want to show small numbers on a clock or dashboard, 7-segment displays have been the go-to electronics option for decades. If you need something bigger — much bigger — then this “Huge Seven Segment Display” from YouTuber “engineerish” could be just the thing.
It features — as you might guess — seven modules, with a base and diffuser on top that snap together, along with connectors that also serve as a convenient path for connecting wires. This allows small three NeoPixel strips hidden in each one to be chained together for control by an Arduino or similar board, with wires exposed only where they feed to the microcontroller/power source. Print files and more info on the build can be found here, while the Arduino code to run it is available GitHub.
Besides simplified wiring, the fact that each segment contains a trio of programmable RGB LEDs means that in addition to counting from 0 to 9, and forming slightly-more-awkward letters, they can produce brilliant multi-light effects as well.
The video below walks you through how the design is assembled, with a simple count-up from zero to nine at the 8:00 mark. More involved purple-ish lighting tricks are shown off at 8:50.