You are the Headless Horseman! Ride through the fields decapitating villagers!
Move the mouse to position your horse and click to swing. chop heads and avoid letting villagers get away to keep your havoc bar filled. Try to get more than one villager in a single swing!
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.