Simple but fiendishly difficult, Tap4 is the new game that's got players scratching their heads the world over.
Bored with sudoku but eager to keep your mind active? Then this is the app for you. With 5 levels of difficulty ranging from 'child's play' to 'impossible', well no one's done it yet.
The rules are simple: tap 4 matching* icons to make them disappear, then another 4 until the board is clear. The catch? There are many different ways to match but very few combinations that will allow you to clear the board.
* Match on colour, number, outer shape or inner shape.