Checkmate of the Day: 3/23/2018

This may not really be the best checkmate of the day, but it occurred at the end of my session. It is quite instructive because it illustrates a common error.  Let's start at the key juncture:

Black is certainly not losing.  He has a strong attack with p@e3.  Is he afraid of losing the rook or of B@d6?   Where would you play for Black?A rook is seldom critical this early in the game.  In any case he makes the usual mistake of Kxf7.  Its best not to lose the pawn on f7, but if you do, it is usually not correct to recapture.  Black, by the way is a 1900 player.

One of the strongest players ChickenCrossRoad, had an opening where he recaptured on f7, but I think he played it only to prove that he was fast enough to get away with almost anything.

Unfortunately in next few moves, White takes the bishop on g5 with check.  Black goes to f8, presumably hoping to avoid the dreaded p@f7+.  White plays b@d6.  It may be more significant that it hems the black king in, as well as winning the Queen.

Black takes the bishop on d6.  This is another huge mistake.  Black's position is awful, but his best bet is to block on e7 instead of taking the queen.  If white then takes the queen black has a tempo try to defend.

One principle to consider is that when you are under attack.  You capture and your opponent recaptures, you then have one few pieces in the theater of operation.

In this situation, it is easy for White to mate.  He can use two pawns or a bishop and a pawn for example.

Notice the pieces piling up by Black's side.  In bughouse, even more than in chess, a trade only benefits one side.  It benefits the side that has tempo.

While my partner was mating on the other board, my board looked like this.  He mated before I could take the Queen.  Is this a legal chess position?  Why or why not?