When projecting a cube from a certain angle, the original four square sides become trapezoidal, and the same thing will happen to the hypercube, as shown in the figure:

The middle cube can be regarded as the cube before extension, and the outer cube is the cube formed by the end points after extension. Just like a cube, six faces are twisted into six pyramids (trapezoid relative to the plane). It is easy to understand why the distorted figure in the projection turned out to be a cube, and it is easy to count that the projection contains eight cubes. It can be seen from the projection that a hypercube takes eight cubes as "faces", every two cubes are adjacent by one face (cubes are adjacent by one edge), every three cubes are adjacent by one edge (cubes are adjacent by one vertex), and every four cubes are * * *.