I'm a big fan of tower defense, it is probably one of my favorite genres even, but that was not enough to hold me to this game. In all honesty it was the lack of upgrades and seemingly linear progress. Usually one of the things that I find are incorporated is that you start small and get to unlock new abilities/ tower levels as you progress that you can allocate to be able to enhance different play styles. When I saw that you can already upgrade each tower to the third level immediately and that you could not mod them I lost interest very quickly. My advice is to hold out on being able to max each character right off the bat and maybe add skill points so it does not feel quite so stagnant and linear. I look forward to your next effort.