once you get to the bombs thsi does get hard.
mayebe I'll come back for all stars.

tough

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.