Oxyd is a 1990 puzzle video game developed for the Atari ST and ported to the Amiga, Macintosh, MS-DOS, and NeXT by Dongleware Verlags GmbH. It is a game of puzzles and tests to restart all the oxygen generators (called Oxyds) on the player's home planet. The Oxyds must be restarted by opening them in pairs of matching patterns, and (in colour versions) matching colours. The Atari ST version was developed with 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 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. There are two-player cooperative levels with one black and one white marble that can either be played by one player, alternating his mouse control between either marble, or by two players playing on two interconnected computers. The interconnection is accomplished by MIDI on the Atari ST, or by the serial ports on other machines. Release Dongleware offered for $4 shipping and handling the first ten levels of Oxyd, and the game was easily obtainable from shareware CDs or bulletin board systems. From