Precomputing a Game Physics Engine's Constants with C++ constexpr

This tutorial builds a compile-time physics constant system for a 2D game engine using C++ constexpr, covering constexpr variables for scalar constants usable as template arguments and array sizes, static_assert for compile-time invariant verification, constexpr functions evaluated at compile time when called with constant arguments, constexpr constructors for literal types fully constructed at compile time, and if constexpr for zero-cost debug/release dispatch without preprocessor macros