Aussie developer here. Twenty is an adrenaline puzzler for iPad/iPhone/iPod with similarities to Tetris, 2048 and Money Idol Exchanger. I initially developed this game because my girlfriend wanted to play Money Idol Exchanger (an old arcade game) on her iPad, but the game has evolved beyond that.
Base game is always free (including a nifty two player mode), but there are extra modes available as IAP, which are temporarily free for this weekend only.
No ads, and no IAP other than this one unlock which is currently free.
Where do I obtain this IAP?