Well...
Although I think the game could be potentially fun, I did run into the same problem as 'antidute'. Even the "higher level" puzzles have multiple solutions. Unless there is something more to the rules you aren't explaining to us.
The game, given the stated rules and not the singular solutions of unknown origins, is also very easy even through the "higher level" puzzles. It would be nice to have puzzles that were a bit harder, that maybe did have only one correct solution.
Also, it would be nice to be able to simply select what you wanted to change the block to, rather than having to cycle through.
All in all the game as it stands isn't very fun and doesn't take much thought. I hope you continue to develop the game because I would really like to play a full version.
5/10 3/5