As others have said, it's pretty difficult game. You have to be exact with everything. Exact with the momentum, exact hitting the bomb button. Everything has to be perfect and that's a difficult thing to do, and tiring from retrying levels over and over. I'm surprised that I could use the R button for a quick retry after a bad move, or hit a button to use a bomb instead of using a mouse to roll over and click it. For these types of games you kinda need those features to make it less stressful.
This game is a bit difficult ! But once you got the game in hand and with certain amount of try, it's possible to finish it. I give not five stars for the difficulty, but four because I got all the medals !
After having gotten three stars on the first 13 levels, I certainly feel as if I have earned the "Lucky" achievement.
That probably sums up gameplay pretty well. That said, it does have a lot of good qualities, and it isn't a bad game, but there are many many instances where I lose momentum on a planet, or have to take the same shot a dozen times and see if I'm lucky.
If I had a little bit more control, it be a better game.
Side note, by some error I haven't unlocked the Astronomer or AstroPhysicist achievements, despite having more than enough stars.