Thank you for the wonderful feedback!
Yes, the dash charge still definitely needs some fine-tuning to make it feel better, as well as visual clarity for when it starts doing damage (which is only after you have reached the maximum speed).
We are aware that a LOT of gameplay mechanics still need proper tutorials, which will be adressed in the future.
Regarding the resetting of all structures: We had once planned to let the player keep built structures of previous difficulties, discarded the idea though due to not finding a proper way to implement it. Might look into it again though, as it's something I would love to see implemented myself, but we'll have to see about that.