So I'm managing through all the puzzles fine so far.

I get to this particular puzzle and at first I was a little stumped and I decided to look around and figured it out.

Puzzle in question + solution is : http://www.youtube.com/watch?v=QZlWMPE9BAA

I came up with the same solution in multiple ways and even applied the solution in the same order (after resetting the blocks to their original positions) but the lever activates the darts..

Any ideas?