First thing you do is well. Activate hard mode. To do that you have to go to the demon that is sitting on a bench inside the church

Once you press 1. He will get mad and activate hardmode indicated by a lightning strike sound which makes the stage and sprites wasteland colored.

You will begin to notice some strange things happen trough out the game, For example, The timer has begun fast fowarding giving you so limited time to prepare for the next wave. The demon would be right about saying that he would "make your life a living nightmare". And also the old skin shop man and priest villager has vanished from thin air. If your up for the challenge then just go ahead. I'm not stopping you.