I offer a small game
To make a competition for the most solved math problems every month. Every month to restart the result and start again. The system should be automatic and with a command to see how many solved tasks you have. For example prizes such as VIP, money, level. The allowed racing time should be from 12:00 to 22:00, for example, because some players cannot play at night and therefore have a balance or at your discretion.
Its not a CSO but i think the players can compet for prizes with a different and interesting way.