Aside from unlocking and equipping power-ups, players will also be able to unlock and equip upgrades. Upgrades range from increasing the maximum hit points of the player, to improving power-up drops, to adding defensive support.
I've had this idea of presenting upgrades as cards, and I thought it would be cool for players to be able to mix and match upgrades by 'building their deck'. As a developer, I had fun designing the cards and the UI for this. It also gave me an idea of creating my own TCG game (hmmmm....) ;)
Cards are classified based on their 'face'-- which translates to the 7 supporting characters of the game. These characters are actually the main character's goblin friends, each having their own specialty. For example, Filipo is responsible for the power-up charge upgrades, while Rethos is responsible for the cart's armor. Athos is responsible for upgrading the power-up drop and drop rates, while Mosha is responsible for upgrading the barn. Kiki, Monom, and Kookai offer support to the player with traps, ranged attack, and siege weapons.