Provides language support for Yu-Gi-Oh! deck files. These typically have a ".ydk" extension. They are used in YGOPro and other dueling simulators. YDK files consist of lists of newline-delimited integers. These integers correspond to the 8-digit "passcodes" unique to each card. (See http://yugioh.wikia.com/wiki/Passcode for details.) Each newline-delimited integer represents one copy of a corresponding card in a deck. Comments may appear anywhere in a file, starting with "#" or "!", followed by (usually) arbitrary characters, ending with a newline. There are three "magic" comments which typically denote the beginning of a new deck (that is, the Main Deck, Extra Deck or Side Deck). Conventionally, these magic comments are of the forms: #main #extra !side The magic comments are highlighted specially in this mode to make them more distinguishable. Putting it all together, a YDK file specifying a deck, - created by someone named Jackson - with the following cards in his Main Deck: - 3x Blue-Eyes White Dragon - 1x Lord of D. - 1x The Flute of Summoning Dragon - and this card in his Extra Deck: - 1x Blue-Eyes Ultimate Dragon - and this card in his Side Deck: - 1x Cipher Soldier would look something like this: #created by Jackson #main 89631139 89631139 89631139 17985575 43973174 #extra 23995346 !side 79853073 Also, YDK mode will calculate the total number of cards in the Main, Extra and Side Decks (in that order), and display those totals in the modeline. The above deck would have a modeline display of: (YDK[5/1/1])