raycasting + floorcasting

raycasting was a very used 3D rendering technique in the 90's when computers had not enough power to display  real time polygonal 3D as today's, it is also called 2.5D or pseudo 3D.
one of the most popular games that used this technique was Wolfenstein 3D and Doom (id software), 
back then games were mostly all written in C programming language 
and assembly (machine language) for speed and optimization purpose, 
one famous programmer who optimized this technique was John Carmack (Doom, Wolfenstein 3D).
there is also floorcasting  a well known technique to render 3D perspective view, 
also known as mode7 in the Super NES video game console (SNES), the SNES was hardware accelerated to do mode7, 
and one famous exemple was Super Mario Kart and F-Zero, even rpg like Final Fantasy VI  used it.
I used this tutorial:
https://permadi.com/1996/05/ray-casting-tutorial-table-of-contents/
so it is recommended to follow it step by step to understand the math behind raycasting and floorcasting.