One rat move

What levels did you only use one rat for the achievement? I only figured out you can complete the first level with one rat. Which other ones are out there?

I actually just did this today and I was having the same problem. The trick is to do it on expert mode so you can use any item. I did the first level with the cannon and also the second level with the cannon. If it doesn't work out immediately, try it again a couple times because of the physics being screwy.

How on earth did you manage to do the second level using only the cannon?

[serieus1]

I wish I could remember. This isn't exactly a game you pick up again and again. All I know is that it's hard to pull this off since there are so many variations to what happens on screen even if you don't move anything that it just makes this too much of a hit or miss type of thing.

I think I did the legit way though, I didn't think to open up expert and get all the rats from the beginning. Not that this is illegitimate, but it sure does help.

I was able to finish the second puzzle with the the single mouse (cannon mouse) as well. I don't remember the exact settings but I changed the trigger to go off quicker (around 5 or so) to hit the ball before it got too low. The angle of the cannon was somewhere between 20 and 25. The combination led to the ball being bounced off the wall and through the tunnels. It took many many attempts but finally it bounced the right way and hit the bomb.

[nimbusland]

I made a video guide:
http://www.youtube.com/watch?v=ldUNByX0DzY