A below average game with paywalls in place to stop you from upgrading. You earn the ability to upgrade but are blocked by needing two items that are not given out at the same rate as the upgrades needed so you must make constant purchases to keep up upgrades. It's not invest some in the game and your given what you need. It's to force you to continually spend as you play the game. It's a download and play for an hour then uninstall game as it's a dead end game set against the player.