If a feature is to be added, it should be compared against these philosophies. If a feature does not fit within these philosophies, it should not be added.
If a feature is to be removed (or changed), the same question should be asked: will removing this feature serve these philosophies?
The Pets Are The Primary Agents
In some games, the player takes on the role of a hero that grows in power as the game progresses, and it's alright for PsyPets to have player-advancement as well, but the main focus is on pet-advancement: you can't build supercomputers, your pets can; you can't defeat the mighty Kundrav - a dragon from Persian mythology - your pets can.
As the player, you provide the pets a good environment and home, giving them the freedom to do these things.
- Gives the player a care-taker/parenting role
- The player experiences success vicariously - when the pets succeed, the player succeeds
The Pets Are Alive
Well, not really, of course, but they should seem alive - as alive as possible! (From a super-philosophical point of view, you might even argue that seeming alive is as good as anything gets, anyway, so there you go :P)
I try to look to theories in psychology, and apply those to PsyPets. The theory that got PsyPets started was Maslow's Heirarchy of Needs, but we're not limited to that, or even to merely theories in psychology. If some day we find a cool way to simulate physics to make pets seem more alive, awesome.
- Allows players to sympathize and relate to pets (enhances the care-taking role, and vicarious success from pets)
- Creates a sense of responsibility for the pets' well-being
The Players Are Part of a Small Community
Whether there's a thousand or there's hundreds of thousands of players, players should feel like they're part of a small community.
- Allows players to sympathize with other players; to help others succeed, and be happy for the success of others
- The players' successes - and the successes of their pets - feels more important