Fun game! I was contemplating making a tower-d/base-builder/roguelike myself but decided it would be too much work lol. There is some concepts here that really work well and I think you've only begun to scratch the surface of the possibilities. Some really nice touches: for example the zombie movement (how *usually* you won't get hit when you move next to them) adds a nice risk/reward mechanism. The items feel varied and useful and I felt myself trying them all out, and utilizing the cost benefit of the weaker ones a lot. I managed to beat "hope" mode by relying mostly on electric fences and (5) shock attack. I also found if you wall up the bridge at the beginning it messes the zombies path-finding up enough to slow them down a bit. I think the genres pair very nicely together, and having a defence game where you are able to control the game clock at your own pace really adds a new layer of strategic thinking to the genre. Overall, solid entry! You've given me some great ideas if I explore this next year.