I enjoyed the game until it crashed after I upgraded the first tower to level 8.
I think the game could do with some music and sounds, because with nothing but silence it gets a bit repetitive after a while. I was only able to upgrade the first tower so my strategy consisted of mainly just supplying ammo in a loot and then finishing any survivors with the last tower.
I think it could do with more things to do, but still I had an enjoyable playing experience.