If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
As soon as you click the play button, a couple of Super Mario images would appear side by side. Though they appear exactly the same, there are five differences, which you need to identify in order to win the game and move to the second picture. The differences are to be identifies in 60 seconds for you to win and move on to the next picture. Once you spot a difference, just click on the same on any of the two pictures and a part of the bar at the bottom of the screen marked correct would turn green. With every wrong click, a part of the mistakes bar would turn red. If you click at five places, which do not have any dissimilarity, you lose the game.