Rules of snooker satisfied that the player was only positioning the ball, and not playing a shot or preparing to play one. When a player commits a foul, the opponent receives penalty points equal to the value of the ball "on", the value of the highest valued ball involved in the foul, or 4 points, whichever is greatest. When multiple fouls are made in one shot, only the most highly valued foul is counted. Penalty points are therefore at least 4 points and at most 7. Not hitting the ball "on" first is the most common foul. A common defensive tactic is to
Black Box (game) each misidentified atom position costs penalty points: ten in the original Waddingtons rules, five in the Parker Brothers version and most computer editions. Different atom positions lead to different average scores - a very easy four-ball game might average eight or nine points to solve, while a very hard game might average 18 points. The most common variant of "Black Box" is played on an 8×8 grid with five (or more) atoms. Five-atom configurations allow for positions that cannot be unambiguously determined by probes. The grid at left shows an example of this. If the fifth atom is in any