The Store can be accessed from the main menu. In addition, the game can be paused at any time in order to purchase upgrades. The mission failure screen also offers direct access to the store. Credits that are earned by playing through missions in the game serve as payment. Every upgrade purchased will be available for the whole game, even when replaying earlier missions or checkpoints. Note: The Store and the upgrades purchased on it are unavailable for the protagonist of the Bonus Missions.