Okay, so, Build 5 is added with a major overhaul! I implemented a main game mechanic which is explained in the first post. I couldn't post a video this time, but a very early demo map, a simple win-lose scenario, and a bunch of other things are added.
The main game mechanism is derived from the idea of two-state floors. Players can "turn" them on and off and eventually, the aim is to be able to reach certain points of the map which are otherwise unavailable.
This is the first major release of the prototype, I hope it's at last something you can evaluate. Everything's available at the link of the first post.