How are my cards stored and how does the upgrade system work?

All cards obtained, whether from a purchase or from a session that grants a card instead of another prize, are stored in the My Cards section and start at Level 1. Over time, users will collect duplicates, which are automatically applied toward upgrades once the required number is reached. Upgrading a card increases its power or speed, and the number of duplicates needed depends on the card’s current level and its rarity. For example, upgrading a Common card from Level 4 to Level 5 requires 20 additional copies.