In Six Differences you are given two animated portraits and as the name implies there are six subtle details that differ between them. Your task is to spot them and click on them with your mouse. As you do so, the portraits will correct themselves, you'll also find a counter hidden with the pictures that will show you how many are left. If you are looking for a hint, press your H key. You can also choose to play with music playing in the background, which I recommend.