Cubes are the easiest collectibles to find in the game. They are obtained by either collecting 8 cube bits or finding entire cubes. There is a total of 32 cubes in the entire game, with most of them being collected by collecting cube bits. Cube bits can typically be found shattered in places all around the game. Entire cubes can either be found in rooms or as the reward for completing a puzzle, although it is more common to get an anti-cube as a reward to a puzzle.
It is possible for the player to get the 32-ending of the game with only normal Cubes, but it is highly likely they will end up getting a few anti-cubes in the process of playing the game normally.