Then, something goes wrong and zillions of computer virus ants invade the net. Numerous files are available for playing variants using the Zillions of Games proprietary software engine. Zillions represents boards and pieces with bitmap images; these can be remapped by the user. Besides defining how pieces move, "Zillions" can define how pieces may be dropped. Two large collections of Zillions Rules Files (ZRFs) soon began to appear. The first commercial usage of general game playing technology was Zillions of Games in 1998. The game rules are specified with S-expressions, "Zillions rule language".