I like the game, but there are some things that really make it almost unplayable on my older computer. Despite lowering the quality which usually works, the game runs really slow.
What's worse, though, as soon as there is a certain number of units on the screen the gun stops shooting when I hold down the mouse button - it makes a shooting noise alright, but there is no bullet. A bullet only appears when I release the mouse button.
There is another threshold where the character stops responding entirely and I have to let go of the WASD keys to get him moving again.
Like I said, overall great game, but a little resource intensive for what it is...