The main purpose of the game is to clean the 4x4 field by merging the figures.
If 4 figures fit one square, it will successfully disappear.
A swipe moves all squares inside 4x4 area. So, you have to wisely choose the move direction to draw the squares you want to merge together.
Merge swipe also merges all mergable squares, so you got to avoid the squares you don't want to be merge to be adjustent to each other.
The game is interesting, challenging, fun, and maybe a little bit addictive.