Fixed Crash Bug and Puzzle

Fixed a bug that would crash the game. Essentially if you pushed a block when it was 'dead' then the game would stall indefinitely. What happened was that I didn't zero the movement vector for the 'dead' block. The rule in puzzlescript language is [moving block | wall] -> [stationary block | wall]. But this would only work for 'alive' blocks and so the crash. 

This was all brought to my attention by Le Slo who also showed me something interesting. The last puzzle in the demo has a solution that I didn't anticipate. As such, I changed the puzzle to reflect my intended solution. It is not only harder but I think more elegant as well.