Okay game, but others are right. That last stage is absolutely cruel. Minus one and a half stars for pulling that garbage.
9 levels to play through, then a perfect run of the same, to get only one shot at a final stage which is just entirely pixel-perfection, and a tiny slip of the mouse (whether by you or mouse imprecision) will end it and you have to do the entire process all over again for just one more shot, etc...
You really have to hope you get lucky. You could grab it and try to slowly scoot it through that area, pixel-by-pixel, but you're just as well to grab the thing and try to gun it and hope for a lucky gun. Yes, in both cases, if it doesn't work, do the entire game over again. (I recommend the gun it and hope you get lucky approach)
You really really really ought to consider making a fair last level, replacing that unfair garbage level 10 with it, and uploading the new version so more people have a shot at this. Yes I don't even care that I had to earn it the hard way and this would give others an easier method. It's the right thing to do. As-is you just really have to be way too particularly lucky to obtain it and you're trolling your players too much with it.
Trust me. If you fix level 10 to be more fair, it won't bother me one bit that others are able to obtain that medal easier than I was able to. And as an added special bonus you'll get a *lot* of goodwill from your players and people will enjoy your game more instead of just being mad at you.