The instructions are inside the game. It shows up at the start and click on it to hide the manual.
This is raycasting, it is a set of rays that projects something 3D. If you want to a project like this, go to this link: https://www.youtube.com/watch?v=M1c5TcdITVs&list=PLy4zsTUHwGJKolO9Ko_j6IStFIJnTYBul&index=1.
