Editing Time control (section)

===Hourglass===
Each player's clock starts with a specified time (such as one minute or ten minutes). While one player is deciding a move, their clock time decreases and their opponent's clock time increases. This is analogous to an [[hourglass]]: sand empties from one container and fills the other. The sum of both clocks always remains the same, and slow moves give extra time to the opponent. There is no maximum amount of time allotted for a game with this timing method; if both players play quickly enough, the game will continue until its natural end.

Use of this time control is uncommon.{{Citation needed|date=August 2020}}