What method exactly can be used to achieve lighting like this? (2d platformer)

So I wanted to know how the dynamic lighting was made in a video game called "Ori and the Will of the Wisps". The technique was explained in a very interesting article I found:

"Using traditional normal maps produces results that appear too 'plasticky', ruining the painterly style. Instead, the artists go in and directly paint lighting on an object. They paint six sides to account for where the light might be shining - such as the left or right side - and compress the results into an RGBA texture. Six directions for each pixel are then tested to figure out the position of the light, while blending between the six light masks."

(https://www.eurogamer.net/articles/digitalfoundry-2020-ori-and-the-will-of-the-wisps-switch-inside-an-impossible-port)

Some people probably instantly know what they need to do to in order to achieve this, but I've never done anything really difficult with rendering, shaders, lighting or whatever it is, so I'm a complete beginner.

So my question is, with what "thing" exactly was this programmed? Just with a normal script, or with shaders, or with something else? I would like to know what subject I need to read into in order to accomplish this as well. (It probably isn't that easy). So if anyone knows with what exactly or even how this was made, I appreciate any response!