Press the green flag. If you see the trees before you click start, click the green flag again. Click on the dog to get a point. No high score will be set for this game. If you click the green flag, your points will be reset (according to the Hints and Tips menu; sorry!) . If you haven't noticed, the pup says "How'd you find me?" if you click him.
I made this using the handy Hints and Tips menu. Background - Scratch Dog - Scratch Tree (to the left) - Scratch Tree (to the right) - Me Coding - Me (technically)