Thanks for the feedback
Suggestion 1: I'm not sure about that. I think it might work if it was synced to a heartbeat sound but as soon as the player mutes the audio, then I think it would look more like the graphics were glitching than moving with the pulse of a heartbeat.
Suggestion 2: I presume the result would be to increase or reduce the flow rate of blood and viruses, right? That would be easy enough to do in code, but I don't know how to implement that from a game-play point of view. Does the user select them? Do they happen randomly? How? Why?
Suggestion 3: Eventually
There's still no UI. Right now I place towers by clicking their initial letter on the keyboard and the tower appears at the mouse position. I also have a few bugs that are bugging me! For example, The "Cutter Tower" occasionally, but not always, has the spinning blades drift away from the end of the cable and I can't figure out why.
My level building system is fully functional now so it's quick and easy to build new levels and waves. There's still a lot of tweaking of the difficulty to try to balance but I think that is something that will always be flexible. Long after a tower defence game is released they still have updates to tweak the balance but I have to get it close to right at least!
I'm considering creating a GUI with sliders to adjust the balance of everything but that will push me beyond the deadline for the compo. Not too much of an issue for me since I'm not eligible for any prizes but I'd still like to have something ready for it.