I learned these low-level bit tricks by reading TempleOS' HolyC source code. I remember feeling like a genius when I worked out what this line does:

dc->color=c++&15;

Hint: it's from this "Lines" demo program, whose source is here: https://web.archive.org/web/20180906060723/https://templeos....

And this is what it looks like when it runs (ignore the fact it's running in Minecraft): https://youtu.be/pAN_Fza6Vy8?t=38