In game development, it's important to know when not to reinvent the wheel: 25 years after Id first flashed the dingy hallways of Quake, we ended up flashing the fluorescent lights in City 17 of Half-Life Alyx in the exact same way.

Make no mistake, this is not just a similar effect: the flickering in Half-Life: Alyx, discovered by redditor AliYil, works exactly as it did in 1998's Half-Life.

In Source, and obviously in both GoldSrc and Source 2, lights have a set list of properties that can be tweaked within the editor. Flicker is controlled by a string from A to Z, where A is total darkness and Z is full brightness. By changing this string, one can emulate the flickering of a candle, a soft LED pulse, or a severely broken fluorescent light, as in the demonstration.

For example, a candle might use the string "nmonqnmomnmomno", but this special effect is generated by "mmamammammammamamamma."

It is one thing for Valve to reuse code from "Half-Life 1". But the developer's engine has its roots in Id Software's groundbreaking Quake engine. Surprisingly, it turns out that this method of breaking the lights may have started with John Carmack's engine, but with decades of 2D game precedents, it is more than possible that the technique goes back even further.

We are used to seeing developers talk about impressive big steps forward in technology, especially when it comes to something as complex as lighting. Still, it's sometimes nice to know that even after decades of progress, a simple trick can still meet its demands.

This article has been updated to credit the original contributor of the first comparison GIF.