Beautiful graphics, cool ships, fun gameplay. But after the first 20 or so levels, you cannot progress without upgrading your ship, so you have to grind old levels for coins. There are no defensive upgrades, so if your ship blows up, you have to watch an ad or spend coins or gems to keep playing. Some enemies spawn or attack in such a way that it is impossible to avoid them. I reached level 24 and uninstalled because it was more frustrating than fun. I would reinstall if enemies did not spawn from the bottom of the screen and if ships could be given defensive upgrades, such as shields or an extra free life.

I used to really like it, I would have given it a 4.5 at least in fact. But I'm dropping it to 2.5 somewhere in the past couple of months. I noticed another reviewer having the same trouble I'm having with moving the players ship in time to avoid missiles. He claimed the ship doesn't track with his finger. I'm having some problem. And to make matters worse, if by chance the ship is syncing with your finger, it pauses the game and gives a countdown. Especially in corners. Super aggravating.

I really like the look and feel of the game, the variety of aliens, graphics & smooth performance. But the app isn't free. Once you get to a certain point the ship is downgraded & you have to pay actual cash to have enough firepower to make it through the boards. Even though I have accumulated more than a million coins from previous successes, I can't spend them on what I need. The upgrades that I have won & purchased disappear before I can use them. And it's missing instructions in many places.