Collection: 4x4
The 4x4 is an exciting step up from the regular 3x3 and is recommended only for those who can already solve the 3x3. The 4x4 is solved by reducing it into a 3x3 by solving the centres and the edges, however, there are some cases that you can run into on the last layer that are not possible on a regular 3x3, these cases require special algorithms. The 4x4 is also complicated by the fact that the centres aren't fixed in place so you have to solve the centres to the right colour scheme or have trouble later.