A few problems
The advertisements really killed it for me too. 10 levels, ad. 5 more levels. Ad. When will the greedy madness end? All I can say is that if you really need the money, get a job instead of making free flash games.
Also, if there is a puzzle with multiple solutions, I'd say allow for multiple solutions. This only seems to be a problem on the early puzzles. But the point still stands that if I offer up one solution that works, I may not follow whatever logic you used to create the solution you came up with, and then I'll sit here forever trying to deduce what I did wrong despite the fact I am right, just not YOUR right.
Ranting aside, fun game. Just a few bugs. Maybe some music would be cool too. Variety of music. Too many games get complained about only having one looping song over and over again.