A surprising miniature

In a recent game I played an opponent well known for his intense opening study. We had played a semi-slav about a month prior and I felt I shouldn't repeat that line having put no effort into learning about the opening we played. So I chose to avoid his opening prep and on move 3 decided to take an odd move order to a stonewall setup. This opening is not known for being particularly ambitious for white (though there are some kingside attacking chances that shouldn't be ignored) and so I was surprised when the game was over on move 13! My opponent resigned facing significant material losses.

Without further delay, here is the game, short and sweet: