Yeah, I get the theme, that makes sense. I may have totally missed this, but was it possible to power-up one of your towers? I think the running around was fine, I liked it, I just didn't know when enemies would be coming and was kinda hesitant to even leave since I needed to restock my towers, haha.
I noticed the indicator on the tower after I lost a couple of times, and I think that indicator was fine, but maybe if the tower faded in and out (maybe a white color), or something to show it was empty could really catch the players attention.
Yeah, it was a game jam, so I get that balancing wasn't really a top priority, but yeah it was still fun :)