Helleeeuuu. We're making some exciting progress in game design! It's Adriaan's department, so I can't speak to the details of what went on in his brain :P But I can show you some of the screen shots I made during testing and explain what's new. First off, I turned more of our tower designs into pixel assets, and added them to our test level. Here are most of them:
We designed a couple of placeholder enemies, and created larger waves:
And We've put assets on spawn points, so it's clear the enemies spawn out of the Rifts:

We've also added indicators to spawn points, to make building decisions more strategic.
And we made a decision to have resource generators remain inactive when built during a wave, to nudge more towards saving resources for 'engine building' rather than stressing optimizing the exact moment the generator is built. (That's the best I can do at explaining it in 1 sentence :P You'll see what I mean in the demo :D). Here's a gif of the new generator!
More in the next update!