Good to hear, it's mostly just that it's a demo and that you're working on what needs to be done, then.
I'd just like to say, I'd be wary of going for 'Enemy is resistant/immune to X so you have to use a variety of traps' and throwing in a load more damage type. It's a common route to take but could lead to bloat and not much diversity in options. Instead of a player spamming the same trap over and over, they'll be just spamming towers like 1,2,3-1,2,3.
Having, say, a tower (door) type that hinders movement until enough 'damage' is done to it and it has to reset, then having an enemy that specializes at breaking in these door-towers (and may have some other properties) would be an example of an enemy that isn't resistant but still overcomes some traps. Fast enemies that are prone to trip-traps (slowed after being tripped), an enemy that doesn't trigger floor traps (but still gets hit if others trigger it / triggers it if they have a certain status effect), an enemy that sacrifices itself to block a trap's hit, that sort of thing. Basically, posing a question to the player of how they should design a set-up to handle a unique enemy, rather than just placing down different tower types. That, along with traps that work well in some environments (long range trap long corridor, push trap to ledge, map water that slows but removes statuses so you might use non-status-dependent traps).
I'm getting carried away with ideaguying but yeah, if you try out resistances just be careful that it doesn't just turn into a different type of trap spam.