Strategy guides are instruction books that contain hints or complete solutions to specific video games. The line between strategy guides and walkthroughs is somewhat blurred, with the former often containing or being written around the latter. Strategy guides are often published in print, both in book form and also as articles within video game magazines. In cases of exceptionally popular game titles, guides may be sold through more mainstream publication channels, such as bookstores or even newsstands. Some publishers also sell E-Book versions on their websites. Strategy guides marketed as "official" are written by game distributors themselves or licensed to a specialty publishing house; Prima Games (a division of Random House) and Piggyback Interactive (a division of Simon & Schuster) specialise in writing official guides for various companies. There are also a number of publishers who make unlicensed, "unofficial" strategy guides, and many of today's mainstream publishers began by making such guides. Typical contents The contents of a strategy guide varies between game genres. Typically, the guides contain: Detailed gameplay information, for example, maneuvers that are not detailed in the manual. Complete maps of the game, which show the placement of all items (including hidden and hard-to-find ones). Detailed instructions for specific locations on how to proceed from there. Explanations of puzzles. Details of enemies, including techniques on defeating individual enemies (especially bosses), the segment for minor enemies is commonly referred to as a bestiary. Checklist of collectible items. Cheats and game editing, although this has been less common in official guides. Walkthroughs to help the player complete levels. Advice on tactics and strategies for use in multi-player (games with multi-player only) Publishing before game release In order to be released at the same time as the game, commercial strategy guides are often based on a pre-release version of the game, rather than the final retail version; BradyGames' guide for Grand Theft Auto: San Andreas included misplaced item locations and a slightly different map, which made some directions impossible to follow. BradyGames rectified such mistakes by offering free errata pages for download from their website. Strategy guides are sometimes published before the game itself is published. This can be risky because there is always the chance that a game will end up not being released. For example, in January 2001, Prima published a guide () for the Dreamcast version of Half-Life, which was canceled late in development when Sega discontinued