This is a very nicely done game. I didn't play for long though, was a bit dull to me. But I really like the shadow/light dynamics, how the block zombies act.
Didn't see any instructions menu. Personally I think its a good idea to implement it just before the zombies come at you. For example, you can fool around within a set x and y to test controls (indicated on screen) and press enter to start the actual game.
Or simpler, just a screenshot of the level, and the instructions on top of it, and 'click or press anywhere to play'.
But of course, the game could use progress. And upgrades are always nice. I'm sure you heard of that flash game 'The last stand'. OK so I digress.. good luck.