Oxyd

Oxyd is a computer puzzle game released for the Amiga, Atari ST, Macintosh, PC, and the NeXT platform by Dongleware Verlags GmbH in 1990.

It is a game of puzzles and tests that challenge the player to restart all the oxygen generators (called Oxyds) on his/her home planet. The Oxyds must be restarted by "opening" them in pairs of matching patterns, and (in colour versions) matching colours.

It was originally developed for the ATARI-ST in the Megamax Modula-2 programming language.

Gameplay
The player controls a small black marble that rolls around, touches things to activate them (Oxyds are opened by touching them), and bashes things to move them. The player has an inventory and can add some items to the inventory by rolling over them. The game's playfield is called a landscape. The player must open all of the Oxyds to progress to the next landscape. Oxyds must be matched in pairs. An unpaired Oxyd will close if an Oxyd of another pattern or colour is opened.

Some landscapes also contain textual clues, which the player can place in their inventory by rolling the marble over them. They can then be selected and read. There are clues on many landscapes: some are helpful, but others are confusing or not so helpful. Other useful items include are bombs, dynamite, spades, keys and computer disks. These items may be placed in the inventory, and can create or destroy blocks, create holes, fill holes, and open doors. There are other interactive blocks, including movable wooden blocks, lasers, mirrors, hidden passages. There are also dangerous areas, including bottomless pits, crumbling floors (which collapse if the marble has been rolled on them several times), slides, pools of water to drown in, quicksand (which the marble will slowly sink in), and assorted traps.

Some levels invert the player's controls, and in the sequel games, the player has to control several balls, which shatter if they touch each other.

Marketing
The Oxyd series had a quite unique marketing method: the games were free to distribute and were easily obtainable from shareware-CDs or bulletin boards. The first ten levels could be played without restrictions. From the eleventh level onward, at various intervals throughout the games, so-called "Magic Stones" blocked crucial parts and passageways of the landscapes, mostly rendering progress impossible. These stones could only be removed by entering a code. A code book called the "Oxyd Book" was sold separately for the price of a budget video game. This book contains approximately 150 pages of code tables matching the information given on the Magic Stone. This form of software protection is effectively using the book as a dongle; however, unlike other games which use the code book protection approach, the game itself was free.

Sequels and re-releases
At the time of its release, Oxyd gained enough popularity to spawn a number of sequels: Oxyd Magnum, Oxyd Extra, and per.Oxyd (also known as Oxyd 2). Additionally, Oxyd itself was a sequel to a lesser-known game, called Esprit.

The Oxyd series is no longer maintained by Dongleware.

Enigma is an Open source fangame with over a thousand different landscapes that can also read the original Oxyd level packs (they are not included for copyright reasons). Also the included "Dejavu" level packs contain levels with similar ideas to the original levels.

Mad Data, with the permission of Dongleware, has produced an official freeware game with the name "Oxyd extra v2.0" (see external links below).

Reception
Computer Gaming World in 1993 called Oxyd "My favorite new shareware title ... an exceptional offering, guaranteed to provide numerous hours of enjoyment".