The Oxyd series is a fun shareware puzzle/action hybrid that plays like a cross between Marble Madness, Macintosh classic Crystal Quest, and Chip's Challenge. The game even boasts a plot: overnight, the (digital) life-supporting Oxyds have closed up and no longer emit vital oxygen. As a result, the digital world is threatened by suffocation and only you (as a black marble) can save it. Your mission is to find all the Oxyds in a given landscape and to open them again. Each two of these Oxyds carry the same pattern or color, and they must be touched in sequence in order to remain open. It's not as simple as it sounds, of course-- your task is made much more complicated by the fact that the Oxyds are scattered over a wide area, and they are not easily accessible. Part of the fun in Oxyd is the fact that many of the objects you will encounter in this world have completely unknown effects, and they interact with each other in a complex fashion. It's fun to discover these relationships and what each object's raison d'etre is, and there seems to be an endless variety of new terrains and obstacles throughout the hundreds of levels. With a good balance between manual dexterity and wit, Oxyd Magnum will keep puzzle fans happy for hours, although the large number of obstacles and special objects mean that the game lacks the elegant simplicity of Chip's Challenge. Note: this download is Oxyd Extra, the last game in the series that was released only on CD-ROM. The game includes only 30 new landscapes, but the best graphics in the series.