SetPlayerWorldBounds

This function can be used to change the player's World Boundaries, thus restricting the places he/she can go to.

Parameters:

(playerid,Float:x_max,Float:x_min,Float:y_max,Float:y_min)

playerid

The player you want to set the boundaries of.

Float:x_max

The max. x-coordinate where the player can go.

Float:x_min

The min. x-coordinate where the player can go.

Float:y_max

The max. y-coordinate where the player can go.

Float:y_min

The min. y-coordinate where the player can go.

This function does not return a specific value, it's best to simply ignore it.

public OnPlayerSpawn(playerid)
{
    SetPlayerWorldBounds(playerid, 20.0, 0.0, 20.0, 0.0);
}