Mortal Kombat is a best-selling 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 fatalitiesfinishing moves, requiring a sequence of buttons to perform, which, in part, led to the creation of the ESRB. The series itself is also known for replacing the hard c sound with the letter K, thus deliberately misspelling the word "combat," as well as other words with the hard c sound (example: "klose" quarters instead of "close" quarters).