The original Dungeons & Dragons, now referred to as OD&D,[78] was a small box set of three booklets published in 1974. With a very limited production budget of only $2000 — with only $100 budgeted for artwork[79]: 26  — it was amateurish in production and assumed the player was familiar with wargaming. Nevertheless, it grew rapidly in popularity, first among wargamers and then expanding to a more general audience of college and high school students. Roughly 1,000 copies of the game were sold in the first year followed by 3,000 in 1975, and many more in the following years.[80] This first set went through many printings and was supplemented with several official additions, such as the original Greyhawk and Blackmoor supplements (both 1975),[81] as well as magazine articles in TSR's official publications and many fanzines. In early 1977, TSR created the first element of a two-pronged strategy that would divide D&D for nearly two decades. A Dungeons & Dragons Basic Set boxed edition was introduced that cleaned up the presentation of the essential rules, made the system understandable to the general public, and was sold in a package that could be stocked in toy stores.[67] Later in 1977, the first part of Advanced Dungeons & Dragons (AD&D) was published,[67] which brought together the various published rules, options and corrections, then expanded them into a definitive, unified game for hobbyist gamers. TSR marketed them as an introductory game for new players and a more complex game for experienced ones; the Basic Set directed players who exhausted the possibilities of that game to switch to the advanced rules. As a result of this parallel development, the basic game included many rules and concepts which contradicted comparable ones in AD&D. John Eric Holmes, the editor of the basic game, preferred a lighter tone with more room for personal improvisation. AD&D, on the other hand, was designed to create a tighter, more structured game system than the loose framework of the original game.[11] Between 1977 and 1979, three hardcover rulebooks, commonly referred to as the "core rulebooks", were released: the Player's Handbook (PHB), the Dungeon Master's Guide (DMG), and the Monster Manual (MM). Several supplementary books were published throughout the 1980s, notably Unearthed Arcana (1985) that included a large number of new rules.[67] Confusing matters further, the original D&D boxed set remained in publication until 1979, since it remained a healthy seller for TSR.[70] In the 1980s, the rules for Advanced Dungeons & Dragons and "basic" Dungeons & Dragons remained separate, each developing along different paths. In 1981, the basic version of Dungeons & Dragons was revised by Tom Moldvay to make it even more novice-friendly. It was promoted as a continuation of the original D&D tone, whereas AD&D was promoted as advancement of the mechanics.[11] An accompanying Expert Set, originally written by David "Zeb" Cook, allowed players to continue using the simpler ruleset beyond the early levels of play. In 1983, revisions of those sets by Frank Mentzer were released, revising the presentation of the rules to a more tutorial format. These were followed by Companion (1983), Master (1985), and Immortals (1986) sets.[82][83] Each set covered game play for more powerful characters than the previous.[84] The first four sets were compiled in 1991 as a single hardcover book, the Dungeons & Dragons Rules Cyclopedia, which was released alongside a new introductory boxed set.