PackRat is a virtual card-collecting game. The goal is to collect a specific set of cards to complete a collection of 10-20 cards. When a collection is completed, you earn a special 'Feat' card. Some of these cards can be bought in markets or stolen from the Rats, while other cards will have to be made by combining together 3 other cards into a 'recipe' card. If a card is a recipe, clicking on it from your game Vault will show the 'ingredient' cards.
There are more than 650 collections to choose from, and new ones are constantly being released. At any one given time, there will be around 10-15 active collections to choose from:
After collections have been active in the markets for a while (usually around 1-3 months or so), they then retire to the retired ticket markets; you can still work on them at this point, but cards may only be purchased with tickets at this point.
You acquire cards by purchasing them from various markets, making them with three other cards ('recipe' cards), trading them, stealing them, and finding bonus cards throughout the game. All cards collected first go to your Pack, which is the home screen for the game. Cards here are only temporarily safe from being stolen by the 'Rats' (unless purchased with tickets), so you want them in your safe and secure Vault as soon as possible!
Collections are thematic, and all cards in the collection are relevant to this theme. For example, to complete a Nursery Rhymes collection, you need a Mother Goose card, a Humpty Dumpty card, a Jack and Jill card, a Three Blind Mice card, etc.
When you complete a collection, you are awarded with a special Feat card; you can get additional Feat badges depending on how that collection was completed. All Feat cards will have the likeness of a Rat on it.
The same collection can be completed in multiple ways, meaning not all completed collections will have the same total amount of cards in them (though they will have at least one of each card represented by the collection).