The most of the games in Sandbox lobby are quick games and do not allow spectators.
The boxes are the little squares in the upper part of the game screen.
Ticking the left-hand box makes nights shorten from 2 to 1 minute, and days from 10 to 5 minutes. Ticking the right-hand box closes the game from spectators until the game is finished.
Do you think the boxes should be ticked by default? Opinions?