remember BC's Quest for Tires?
Very nicely done--well put-together, easy controls, interesting ideas on obstacles, and the progressive tutorials were an excellent idea. Oh, and the smurfs were a nice touch, too, hehe.
You might want to make a few less levels, though--ten is a whole lot when the levels are that lengthy. Either that or some more variety in things to do, like what you had going with the Slimers and whatnot.
Overall, a very nice piece of work, but could use a little more variety.