Yeah, unusual but nice :D

1- the black king is open and so exposed

2- the black squares around the black king so week

3- underpromotion to knight to maintain the initiative and  achieve checkmate

4- all black's pieces so away from action

All this helped to achieve this humiliating  checkmate.

And look to :( if you want) 

1-Weak Color Complexes Explained by IM David Pruess

2-Essential Checkmate Patterns by FM Thomas Wolski

3-Exclusively Checkmates by IM Jeremy Silman and others 

4-Squares and Rules  by IM Jeremy Silman and others  

all in chess mentor

hmm:)

many solutions possible but this way is the fastest

great puzzle.

Nice but what about 3.Nh7f6 ?

what about 3. Nhf6+?

ah this makes it mate in four :)

easy

yeah, I think 3. Nhf6++ is cooler

Nf6 might be less desirable is b/c it would permit the response of Qh7 (so only an extra move)

beautiful moves

new kind of puzzle

oh, yeah, that's true... didn't see that

nice

good one.

I Like it...very good

3. Rf8#

very cool.