Thanks for the feedback. Just to clarify the Ads in the game, you will get 1 ad after playing the game and consuming all your lives without completing the mission (i.e. reaching the portal). Also, you may get an ad when selecting the mission, this is random with a 45% chance of getting one. There is a way to eliminate all ads and unlock the more advanced ships (faster, more lives, more blasters and more shields) by getting the in app purchase option.
But, we will look to remove ads and make them more optional (i.e. reward videos) in order to improve the spaceships options per game. Hope this will make things better but we need way to support development.