Replace the second paragraph of “The Grid” with

Tic-Tac-Toe is a game that is played on a Grid which is split into a number of rounds. In a game of Tic Tac Toe, each Player uses their Symbol. Provided they have not already made a move within the last 20 hours and within the current round, a Player can make one move. A valid move consists of adding your symbol to exactly one free cell (removing ‘_’ if it is in that cell).

In the same rule replace

Once a round ends, any player may Reset the board by performing the following atomic action:

with

If the current round has ended, no further moves may be made for that round and any player may Reset the board by performing the following atomic action: