Mortal Kombat, sometimes written as Mortal Combat (commonly abbreviated as MK) is a series of fighting games created by Ed Boon and John Tobias. Mortal Kombat began as a series of arcade games, which were picked up by Acclaim Entertainment for the home console versions. Now Midway Games exclusively creates home versions of Mortal Kombat. It is especially noted for its digitized sprites (which differentiated it from its contemporaries' hand-drawn sprites), and its high levels of blood and gore, including, most notably, its graphic fatalities—finishing moves, requiring a sequence of buttons to perform, which, in part, led to the creation of the ESRB.