In the game there are a grid of hearts, you have to match the hearts by swapping them. The hearts will be matched if a line of 3 or more hearts of the same kind are there. When some hearts are matched, new hearts will be created. You need to match hearts as quickly as possible in order to advance to the next level.
A context menu should be shown when right-clicking or, on touch devices, long-pressing in the game. This menu especially allows to play in full screen and control the volume.