# Collections for Twitch cards, inventories and achievements

Build a Twitch collection that viewers fill from chat, such as trading cards from a !pack command, an inventory or a list of achievements, with a catalogue you fill from a spreadsheet.

## What a collection holds

A collection keeps many items for each viewer, and each item has a count: Pixel Pup ×3. Use one for trading cards a viewer opens from packs, an inventory of potions, or achievements, where an item is held once. A variable holds one value; a collection holds a list of items that flows can add to, remove from, check and read back.

## Fill the catalogue

The catalogue is the list of items a collection can give out. Add them one at a time or import a CSV, so the card opener draws only from cards you have listed. The guide shows the file layout and the import step.

## A card opener for chat

Viewers type `!pack` to open a pack. A flow picks items from the catalogue and gives them to the viewer, and a `!cards` command shows what they own. Free is enough to run the opener from start to finish. [Collections for cards, inventories and achievements](https://bloopbot.com/docs/collections) has every step.

## Look up, give and take

A flow can look up a viewer's items, give an item or take one away as they earn or spend something, and the guide shows how to build the lookup command yourself. A give to a viewer who is already full follows its error path, so your chat can say so instead of failing quietly.

## Share a collection in a pack

Collections can travel with a pack. Whoever installs it gets the collection and its catalogue, and can change them from the Collections page.