What rule does he change first? What happens?

Women experience estrus, not menstruation

Josh was not convinced this was real, but he wanted to experiment. As he considered his choices, he didn't just want to type "all girls are naked," nor did he want to just swap gender roles; he'd heard enough complaining about 'male-privilege,' and whether it was real or not, he didn't want to give that up.

But then he remembered the other thing women complained about often: period pain. After some consideration, Josh came up with a fun idea to test the app that could be helpful to everyone.

**Instead of a monthly period, human females go into heat, an estrus cycle, during which they experience extremely elevated levels of arousal and a near-desperation for sexual intercourse for 3-6 days per month. This doesn't change or replace anyone's base level of libido on any other day.**

Saved. Change Accepted.