An elementary proof of the Harnack inequality for non-negative infinity-superharmonic functions

We present an elementary proof of the Harnack inequality for nonnegative viscosity supersolutions of Delta(infinity)u = 0. This was originally proven by Lindqvist and Manfredi using sequences of solutions of the p-Laplacian. We work directly with the Delta(infinity) operator using the distance function as a test function. We also provide simple proofs of the Liouville property, Hopf boundary point lemma and Lipschitz continuity.