Note on a weakly over-penalised symmetric interior penalty method on anisotropic meshes for the Poisson equation, Ver. 1

The purpose is to make an easy-to-understand note of "Special Topics in Finite Element Methods." There might be typos and mistakes. Therefore, I do not take any responsibility for unauthorised use.
Comment: 20 pages. arXiv admin note: substantial text overlap with arXiv:2212.03822