Thanks so much for the feedback. I think this hits on a lot of things I want to improve/add.
- Higher difficulty levels add "extra" challenge by adding a few scaling spawn groups from wave 6 onward. Specifics aren't really important though if it doesn't work and even in my own testing I do agree it's barely tangible if at all. A few intended changes that may address this larger issue;
- Adding "elemental" units. Removing material randomization and using color and effects to convey an enemy is resistant to some types of damage.
- More unique traps and more damage types/status effects.
- Better trap balancing with a specific focus on making elemental/status combos stronger.
- Making the top tier units stronger but less numerous.
- Push traps actually pushing alive units around is something I've wanted to do but is a performance concern. It is something I am definitely working towards supporting though.
- Navigational issues are known and I am slowly improving UE's crowd path following system.
- Single item building is coming very soon. Will be making it so that shift left click allows continuous building.
- Manual wave start is coming very soon. Internal code is done - just needs UI and a keybinding setup.