This could be used for both for games that allow you to pit the CPU against itself (e.g. various fighting games) and for kinetic novels (such as True Remembrance) which don't offer the player any choices,

Edit:Zero Player could also be used for the Nintendo games that include "Super Guides" that can beat the game for you.

I also think it'd be helpful to specify how many players a multiplayer game allows.

Adding a "zero player" option is a little difficult as it's not always obvious if a game supports it. Generally speaking, the back of the box will reveal how many players a game supports (though this information is sometimes buried on older titles), but they almost never include information around the scenario you're describing. It's also a little debatable that "zero" applies since it requires some input from a player to at least initiate those modes. An interesting idea for sure, but a bit trickier to implement (with reliable data) than one might think.

Storing how many players a game supports is a little more doable, but I'm hesitant to make any changes at the moment. Currently, the "play modes" are associated with a game entry, which makes sense at first...but different platforms have different play counts and in some cases, different online options (meaning some have online and some don't). This is something I plan to address in the future, but in terms of data entry, getting the checklists entered is my top priority right now.