Jiraiya's Peeping Hole

You control a cursor, clicking on one of three nearly identical images to find a subtle difference before a timer runs out. Each round presents a new set of pictures, often with a comical or risqué theme, and you have to spot the single altered detail. The pace is fast, and the difficulty comes from the timer pressure and the increasing similarity of the images. It feels like a test of your observation skills under a constant, gentle rush.