The Rubik's Revenge is the 4x4x4 version of the well known Rubik's Cube. The main difference is that in this case the puzzle doesn't have fixed center pieces. Test your skills and try to solve this cube online with this 4x4x4 solver.
Hit the Scramble button to jumble the cube, then try to solve it using the rotation buttons. You can use the same F, R, U, B, L, D buttons which you have used for the online Rubik's Cube simulator. A couple new rotations are coming in here. To rotate two layers at the same time press the buttons indexed with 2.