Backpack

"Carries materials and items. Upgrading increases material carry capacity."

About
The backpack is available from the beginning of the game, giving a starting capacity of 5 Slots, each slot having 4 notch spaces. When a material is collected it moves to the first available capacity slot from left to right and the 1st notch space will be highlighted to indicate 1.

The notches replace the common used display in other games that usually show your item amount as a number x2, x6 etc.

Extra Slots
You can improve your backpack with craftables and skills aswell to increase slots and notches.

Skill
The pack rat skill will add 1 extra material slot per level, giving you a maximum of 14 Slots if your backpack is at upgrade 6.