Doom (1993 video game)
Because id planned to self-publish the game, as the game neared completion they had to set up the systems to sell the game. Jay Wilbur, who had been brought on as CEO and sole member of the business team, planned the marketing and distribution of "Doom". He felt that the mainstream press was uninterested in the game, and as id would make the most money off of copies they sold directly to customers—up to 85 percent of the planned US$40 price—he decided to leverage the shareware market as much as possible, buying only a single ad in any gaming magazine. Instead, he reached out directly to software retailers, offering them copies of the first "Doom" episode for free, allowing them to charge any price for it, in order to spur customer interest in buying the full game directly from id.
List of Doom source ports
Chocolate Doom is a source port for Windows, Linux, macOS, AmigaOS 4, MorphOS, and other modern operating systems that is designed to behave as closely as possible to the original DOS executable ("Vanilla Doom"), going as far as to duplicate bugs found in the DOS executable, even bugs that make the game crash. This involves more than just leaving the bugs in the source code. Several bugs present in the DOS version (for example, the sky bug in "") were fixed in the released "Doom" source code, so these bugs were re-created for Chocolate Doom. The first version of Chocolate Doom was released on September 7, 2005. As it is designed to be as close as possible to the DOS executable, it has no new features and lacks high resolution support. It supports OPL3 music emulation, as well as the standard MIDI output on its host operating system. It is a popular test engine for level designers, and among players who prefer unmodified Doom. By default, it simulates the behavior of doom.exe version 1.9 running under Windows 98, although it will simulate the executables from "The Ultimate Doom" or "Final Doom" if it detects their respective IWADs. The latest version of Chocolate Doom, version 3.0.0, was released on December 30, 2017.