Not gonna argue with this, I just wanted to point out that it's not without mistakes. For Students of the 12th grade it's super well done. For those more concerned with correctness and completeness: For example saying a basis is a _finite_ set of vectors is not generally correct. And I would like to have seen that the Pauli matrices generate all single Qubit rotations. And saying that a bra in itself is simply the conjugate transpose of a state or that <bra|ket> would simply be a multiplication ommits all the cases in which the state is not a simple numerical vector in some basis but perhaps a function of many variables. So read it with caution, but read it nonetheless.