When you hit the slot machine, the vault gradually fills up. Once the vault reaches a specific amount, you have the option to purchase the accumulated energy.

Please note that after a vault purchase, the bank resets. This means your vault has now been upgraded to level 2, and it needs to be refilled by hitting the slot machine again. This reset and upgrade process is part of the vault feature, allowing you to continue earning rewards as you play.

The vault is structured with 3 levels, and the capacity expands with each purchase:

Level 1 capacity: 500

Level 2 capacity: 1250

Level 3 capacity: 2000