The puzzle requires players to take the phrase "the end of the world!" completely literally.
The puzzle succeeds by leveraging standard human panic and gaming instincts against the player.
The correct answer is to click the cloud .
The Lethal Hutchinson Effect: A Guide to Question 66 on The Impossible Quiz
To the uninitiated player, the solution seems obvious. The question asks for the "lightest" block. Visually, the "H" block is significantly smaller than the cloud. In the physical world, a small hospital sign is lighter than a giant cumulonimbus cloud. Therefore, instinct dictates that the player should click the "H."