Heheh, I was actually playing a game about the time you said that, but I didn't notice your message.
With the 60 sec build up time I meant before the first wave spawns in the game (i often run out of time and my first wave is empty, then enemy gets the mid and they win with the gold advantage, or I can't really plan). You can simply pause the gold generation for the duration, if that's a pacing issue.
Your game is good, I would expect a lot more interest coming your way.