Move around with wasd, up and down are q and e. Look around with <^\/>. With the right movements, you can see a cube. If you want to see different things, check out the code for examples and use https://turbowarp.org/640753279 I might add lines and triangles later.
I made this fifth attempt without any tutorials, see https://www.geogebra.org/3d/wnbpv4jv for visualisation. When you use the code, please give credits ;) You can add points in the list points, structure is x1,y1,z1,x2,y2,z2,x3,y3,z3 etc.