Update the demo, it now includes some sound effects (some are still a bit wonky, the machinegun will sometimes not use its sound effect, sometimes it does), some great ambient music by Aakaash Rao from Note by Note studios, and a bunch of optimizations.

Try it out directly here:
https://dl.dropbox.com/u/13425402/Tough%20to%20Kill1.5/index.html

In the main menu, only the 'Play' option currently does anything.

The environment is a bit more robust and explosions not quite so large, so there is now wall and window damage graphics as well as their broken counterparts. When zombies come in contact with flames, they will burn to death. Goliath behavior has been modified and now move much better. Magma monsters have been added that spew chunks of molten lava which will set things on fire (including zombies!). Landmines now project sharpnel in all directions while explosive barrels set things in a radius on fire. Fire slowly damages enemies over time (but will quickly kill most low-end zombies). However, fire and explosions will not work against Magma monsters.

Anyways, try it out and I hope you enjoy it! If you want to check out the KS page, the link is in the original post. Thanks!