This game could easily be a 5 Star game if there was more to it, at the minimum more planets or moons could have been added before releasing the game. - perhaps once at Europa have different destinations one could select that could require shorter altitudes but also give less reward for the number of settlers resting thereon. - There’s other good ideas in the comments here, like aliens, and birth causing population increase, and more. You guys have an addictive game on your hands here, you should take advantage of that and make it last longer, put more into it. The longer people spend playing your game the greater the probability they’re going to spend real money on coins or specials and the like.