The skybox texture is downloaded from:
https://learnopengl.com/Advanced-OpenGL/Cubemaps

The program itself is just a modified version of the OpenGL
example program that comes with SFML documentation.

The example code rotates a cube. It can be found
in the sfml-opengl-example/ directory.

The mathematics that rotates the view and moves the player
turned out to be surprisingly simple. It really surprised me
how simple it becomes when all the vector-class abstraction
is removed (from earlier code that I have written elsewhere).

Written in 16—21 February 2019
Copyright © Joel Yliluoma — https://iki.fi/bisqwit/