JezzBall

JezzBall is a video game in which red-and-white balls, referred to as atoms, bounce about a rectangular field of play, or room. The player advances to the next level (with correspondingly higher numbers of atoms and lives) by containing the atoms in progressively smaller spaces, until at least 75% of the area is blocked off. One gains a bonus for eliminating more than 75%, which is calculated from the percentage over 75% that one manages to block off. One must do this while racing against the clock. It is similar to Qix, which was released during the golden age of video games.

JezzBall was programmed by Dima Pavlovsky and introduced in 1992 as part of the Microsoft Entertainment Pack, and also in the later Best of Windows Entertainment Pack. The game is named JezzBall after Jez San, who was a contemporary of Dima at the time. Despite Microsoft withdrawing support in 1996, it still has a dedicated fan base. While JezzBall is available from many abandonware sites, there are several open source and shareware clones of the game that can be legally obtained. No fewer than eight such clones exist, covering nearly every major desktop and PDA operating system.

Gameplay
''The purpose of the game is to contain the atoms within a room at most 25% the size of the initial room. By using the left click to create walls and the right click to rotate the direction of the wall-building device (WBD), the user must contain atoms in smaller and smaller rooms. When a room is made that contains no atoms, the room disappears. The amount of black on the screen is displayed as a percentage, and when this percentage reaches 75% or more, the level is won and play proceeds to the next level. The first level has two atoms, and each subsequent level has an additional atom. There are an infinite number of levels during play, so that one can never "beat" the game. However, there are only 49 distinct levels, and upon beating the 49th level (containing 50 atoms), the subsequent level is merely a repetition of the 49th level.''

''The player begins each level with the same number of lives as there are atoms in that level. The location of the cursor on the screen defines where the wall will originate, and this position can be termed the WBD. When initiated, two beams of "potential-wall energy" extend from the WBD as rays (in the mathematical sense) until reaching the perimeter of the current room. These two rays operate independently of each other. Upon reaching the perimeter without being hit by an atom, a potential energy ray (depicted in either red or blue) turns black and now serves to further section the room. Should an atom collide with only one of the extending energy rays, that energy ray disappears and a life is lost, but the other energy ray continues extending towards the perimeter. Should an atom collide with the other energy ray, another life would be lost. However, should the second energy ray reach the perimeter of the room, a partial wall will be produced. Two lives are also lost if an atom collides with the energy rays at their combined source (where they meet). The corners of the head of each energy ray are protected from being hit by an atom.''

This historical game description is therefore quite similar in rules (if balls are substituted for atoms) to the one used in a current clone game at The KDE Games Center.

Tactics
The fact that the two energy rays produced by the WBD act independent of one another is the basis for the stovepipe method of atom capture, and may speculatively be the only method of play that will allow advancement to higher levels. This is because, as the number of atoms increases, it becomes increasingly more difficult to remove parts of the room. Stovepipes are made by intentionally allowing an atom to hit one of the expanding energy rays (thus sacrificing a life) while making sure the other energy ray does in fact succeed in producing a partial wall. The closer the WBD is to one side of the room, the higher the risk is of losing one energy ray to an atom collision, and at the same time, the higher the chance is of securing the other energy ray of producing a partial wall.

Clones
Clones of the original JezzBall normally offer updated graphics but vary slightly in timing and scoring from the original.

Many of these clones are shareware, limiting non-paying users to only a handful of levels. Many of these are found on JezzBall.com, an unofficial Jezz Ball page that is at least partially funded through the sale of these clones. Others, including IceBreaker and kBounce, are cross-platform, free software, open source games that are available on a number of operating systems. Some are skinnable; The open source Icebreaker's default skin varies radically from JezzBall, using Tux, the Linux mascot, in place of balls. Silverware Games' Jezz Cubed offer dramatically different interfaces from the original JezzBall, adding three dimensional play, giving the player a cube to reduce by growing planes instead of a plane reduced by lines.