Critical Seeker

Critical Seeker is a single 'spot the difference' game from Australia.

Players are shown two almost identical pictures and must spot the five differences between them. Each picture is timed and the player loses time for random/incorrect clicking. Pictures are shown in groups of five and at the end of the round the player is given a score. The player has no control over the pictures being shown, the game selects them automatically

The game documentation says that this is a freeware game, however registered players get additional pictures and they do not get a nag screen popping up and staying on screen for five seconds