The avocados are running from Santa's house and Merlin is attached to the slaigh by a rope. Guide the Merlin to the sides avoiding obstacles and also getting the presents the avocados are throwing from the veicule. Merlin can't take much damage you'll only be able to hit four obstacles otherwise christmas is doomed.
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.