It's 2048, but the tiles are birds... and they sing. Slide two of the same bird together and they merge into the next, rarer one up the ladder… and you hear it: a real recording of that bird's call. A little Spotted Pardalote becomes a Ruby-crowned Kinglet becomes a Splendid Fairywren… all the way up to a Hoopoe (that's your 2048), and if you're good, a Kea and a Superb Lyrebird.