I was playing a 2 minute game vs the computer and was valiantly trying to finish winning a simple K+R vs K  mating sequence before I timed out, when the computer suddenly told me "draw -insufficient material". Huh? What am I missing?

 

http://www.chess.com/livechess/game.html?id=178868784

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Black cannot give checkmate because he has insufficient material. So when you go trough your clock it's a draw and not a win for black.

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OK, thanks. That really bakes my noodle but I`ll take your word for it- I can sort of see the intent.

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The other alternative is that you lose for running out of time.

BLACK has insufficient material. I assume you time run out. Took me awhile to figure it out as well  :)

King+rook vs. King is one of the harder mates for little kids learning chess. We usually have them practice it a few times till they learn it.

Yes, I ran out of time.  When I reflect a bit more, it makes some sense. Ignoring the clock aspect, theabsolute  worst thing I could possibly do in the game is to lose my rook, in which case it`s a draw. So it`s therefore not reasonable to judge the game a loss for me.  It`s just very counter-intuitive.  Next time, if I am playing against a lone king, I know I can safely sit on my duff and not even make a move, and at least get a draw :-)

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LOL. Even though I`m middle-aged, I keep getting stymied for a couple of moves by the mechanics of it, although I am dead certain that I can eventually nail it. But to pull it off in a 2 minute game with the clock running down eludes me most times :-)

The main thing to remember is that the rook should be used to restrict the amount of space for the lone king. You want to put the king on the last row and then have your own king eventually align itself with the other king so that the rook can deliver the check mating move.