Black has played a version of the Scandinavian Defense that allowed multiple tempi on the Queen. After losing three tempi in the beginning of the game, Black plays the inexplicable 13…Qd8, returning to the home square for no reason.
Perhaps he had ideas of swinging the Queen over to attack, but it would take a few moves to get in any kind of attacking position, and he would likely have no other pieces in the area by the time he got there. His only other developed piece is easily kicked or traded by then.
In any case, we eventually come to a position where White can kill off his opponent with a forced mate. I didn’t play it in the game, although in retrospect it does not seem too hard to find if you are looking for tactics, which I should have been giving the overwhelming attack and Black’s total lack of development and coordination.