Yeah, I definitely need to reduce the difficulty a lot. It's funny, during development I was worried about the game being too easy, and now it definitely seems almost impossible to win.
I didn't add a speed toggle because I was hoping there would be enough to do during the wave to keep the player entertained. They can manage their base, and I had planned on allowing them to pay money to spawn units at any time but that got cut for time. But in hindsight I'm glad my game doesn't have it, because that's what distinguishes my game from all of the other reverse-tower defense games in the jam.