The prize at the centre of Peter Molyneux's Curiosity: What's in the Cube? app will not be "a huge pile of money", the designer confirmed today at Eurogamer Expo.
Neither is it a sports car, a dead cat or Half-Life 3, he added. But it will "change your life forever".
Molyneux revealed plenty of new information about Curiosity during his Eurogamer Expo developer session, where members of the audience were invited on-stage to test out the game.
The app is currently in submission at Apple, and could launch within the next 10 days.
Curiosity's huge cube is made up of 60 billion smaller parts - making it large enough for everyone on Earth to be able to tap it 10 times each.
Those who tap more will have a greater chance of winning, Molyneux revealed. And, as layers of the cube are peeled back, players will find other surprises waiting for them.
One could be that the layer underneath contains photos of the current most prolific tappers. Some layers will have special features or mini-games, including a level that may play like Minesweeper.
Some of these challenges will make up the 22 experiments that Molyneux's studio are creating. The next app, Cooperation, will likely include several more. Data from these will then be turned into the designer's next big project, Molyneux said.
Watch the entire session below.