[oneeyedpigeon]

'Move numbered tiles around a tiny 2-dimensional grid, combining same-numbered tiles to create higher-numbered tiles in their place. New tiles spawn each time you make a move, and the game continues until the board is completely full and you can't make a further move. Score points for higher-numbered tiles.' There are nuances, but that pretty much sums up most of the gameplay of Threes and the 2048 clones; I don't know how you can claim, with a straight face, that the latter are not clones of the former. Even if some ancient prior art surfaces, the timing and the direct references in app descriptions pretty much guarantees this.

[protomyth]

By your definition and not being allowed to use "ancient prior art" then yes it is a clone but so is Sonic the Hedgehog. I felt it plays much different.