For Pokemon fans that don't know how to play the collectible card game, you'll soon be able to learn by playing on your phone for free. I got to spend time playing an early preview of Pokemon Trading Card Game Pocket,

Pokémon TCG Pocket has the workings of a slick virtual trading card game

Now, if you just want to create custom cards for your own home games and personal enjoyment, you can just use the existing lore and rules of the games you already play. However, if instead you want to make your own original game, a tool like ChatGPT is perfect for coming up with a template for your rules.