That was awesome Captain Coder, tysm.
For those getting stuck around wave 4 - try not to think of this as "tower defense". It's a logic problem or math equation that you need to solve. The heroes come into your dungeon and make mess. The damage, healing and steps between everything are known quantities - you clean up their mess by optimizing the dungeon - and use the "summon" tab to move the monsters to the best place to achieve this.
The tut was gonna explain all this more clearly ofc, but we ran out of time and had to cut it ;(
Oh, the colored border around your monsters shows the elemental damage they suffered, so you can optimize your tea making :)