Don't shoot the puppy!

It's the easiest/hardest game of the year! Whatever you do, don't shoot the puppy. Despite the cuteness of the wee pup, it's easier said than done. I so badly wanted hints, but I'm happy that I figured out how to win on my own. All I'll reveal is that there are 15 levels, so you don't have to waste any more time than necessary wondering when/how the game ends (albeit in anticlimactic fashion).

Link courtesy of Elephant Larry's Alex Zalben.