Help with Challenge: Mate in 2 number 6

[jimmylh.geo]

I need help with one of the Challenges. It's the mate in two number six one. My pea sized brain can't figure it out apparently.

[Ziggy]

This one involves a queen sacrifice, a theme which repeats far too often in these puzzles.

Qc5+ (forces black to take your queen with black queen) followed by Nf4#

[jimmylh.geo]

Thanks, I must be blind. lol. I stared at this for an hour an could not see it.

[Ziggy]

Not an obvious thing to do and something I've rarely encountered in real matches. I can understand it's a valuable lesson for someone new to chess as high value pieces are often sacrificed in endgame but I found that so many of the subsequent puzzles repeat this same solution and require little thought.