https://www.geeksforgeeks.org/static-keyword-cpp/
https://www.internalpointers.com/post/c-rvalue-references-and-move-semantics-beginners
nullptr https://www.geeksforgeeks.org/understanding-nullptr-c/
shared_ptr https://www.acodersjourney.com/top-10-dumb-mistakes-avoid-c-11-smart-pointers/
private inheritance https://www.bogotobogo.com/cplusplus/private_inheritance.php
rvalue https://docs.microsoft.com/en-us/cpp/cpp/rvalue-reference-declarator-amp-amp?view=vs-2019