Age of Copywriting

One of the most interesting things discussed in "The Age of Cybernetic Systems" was the way that video games go through the copywriting process. Instead of providing code, software developers provide video of the game being played.
In the case of Pac-Man, this was very important when the court was deciding on whether or not K.C. Munchkin was infringing on the Pac-Man copywrite. In the end, it was decided that "A person who is entranced by the play of the game, 'would be disposed to overlook' many of the minor differences in detail and 'regard their aesthetic appeal as the same.'"
This brings an interesting question to the table though, because there are many games on the market that are"similar" to others, and I would like to know how it is decided when something is "too similar" just by looking at the video instead of reading the code.