Here's how it works.
1) A challenge is posted.
2) The next person who posts accepts the challenge, and must do the challenge within the next 5 days. If a challenge is accepted on a Tuesday, it must be completed by the end of day Sunday. ETC.
3) The next poster may also "throw a flag" on the challenge if he believes it to be too difficult. If this is done, the original poster must perform the challenge within a week, or the poster who threw the flag gets to pass and names the next challenge.
For each challenge accomplished, a poster gets 10 points.
If a challenge is failed, the person who posted the challenge gets 10 points and the person attempting the challenge loses 10 points.
If a challenge is flagged, the person who posted the challenge gets 10 points if they accomplish the challenge, and the person flagging loses 10 points. The original poster also gets to call the next challenge.
Note: If someone posts responding to a challenge after someone else has accepted the challenge, that post is ignored. Only the first person accepting qualifies to attempt the challenge.