Excellent! Graphics are good, the game is fun. Gets tougher as you go, but not so quickly that I just get frustrated because it's "impossible" to win. I might have to restart several times, but not so often that I just quit playing. Actually, it's addictive once you start.
The one negative is: programmers need to give SOME instruction on upgrading the ships, having multiple ships in play, the drones, and other equipment available for use. I've had to trial and error figure out these things.