In this update I've attempted to address a few issues that were raised by various individuals and added in a "hardcore" difficulty.

The new hardcore difficulty is a real challenge for only the best of players. Enemies are the same as in "Hard mode" but the maximum number of enemies allowed to spawn at one time is now 12 (up from 10 in hard mode) and in hardcore mode there are no health kits so all damage is now permanent!

Another minor addition is that now, hovering over the four difficulties will display a little text box with some info on the difficulty so you can better choose your desired level of play. 

Bug fixes include: 

Attempted to fix enemies not spawning at times by ensuring that they cannot get stuck outside of the map.

Hope you all have fun, please let me know what you think of the new difficulty, thanks.

Mr J