Congruence

Grab a tile and drag horizontal or vertical to match 3 or more of the same shape and colour. 

Matches are locked together once they're made, so you have to tap on the match once you've lined it up. Plan ahead to get as many matches as you can with the set of tiles you're given. 

Press the stop button at the top of the screen to end once you feel like you can't do any more, or rewind to a point where you feel like you could do better.