Fun at first, eventually the difficulty surpasses your upgrades which forces you to purchase upgrades with real money or you can't progress. Got to about lvl 30 and the enemy had a power 10000 stronger than mine. I'm not spending real money to upgrade my ship so I'll have to uninstall since I can't beat the enemies anymore. Also would like to point out that ads pop up all the time, even when not playing the game, ads pop up on the menus. Didn't use to be this money hungry. Disappointing