Modifiability – moddability is an essential part of contemporary games, especially digital games. This is a parallel feature to the concept of mass customisation of products in “more serious business”. It starts from, where in Pokemon Go, the player can buy and choose clothing for their avatar. It’s deeper, when games provide downloadable content (DLC) that provide more outfits for the character, but possibly also more different equipment, and even more story to the game. The fundamental level is, where the players can create such extra content and provide it for other players to include in their games. At the deepest level, and actually, in it’s original form, it is when players reverse engineer games, hack them, and provide modified versions of the games with new features.
Game modding started out from replacing the graphics and sounds with new ones, often for comedic purposes. Essentially this was borderline illegal, especially distributing such games, as it was both altering someone’s immaterial property, as well as committing unauthorized redistribution of someone’s immaterial property. Lot of the game industry, however, took a constructive approach here, and designed their games so that they would be more easy to modify. For example, id Software packaged the level maps of Doom so that it was easy for a person to replace the files and play the game in their own created world!
Later on, this tendency has only increased, and several games actually even market themselves by their wide possibility to make modifications. In my perspective, the epitome of this has been Civilization V, which was richly providing modifications, where you could turn the game into X-Com/Laser Squad -like tactical soldier game, or into Starbase Orion -like galactic empires game. The game provided a complete interface for full customisation.
This likens software such as game construction kits already in 1980’s for 8-bit computers that provided with basic language designed for game development and editors for graphics and sounds. Modern versions of these are “game engines”, such as Unity and Unreal. The difference here is that these kind of kits are more like workbenches for people to take very raw material and create a game of pretty much their own inspiration. In game modifications, people take a game, or at least a highly refined framework, and form it into something different. It’s like taking an empty drinking bottle, filling it with water and stuffing it upside down into a flower pot to turn it into an automatic plant watering system, or like taking a bottle of soda and stuffing a pack of mentos into it, to make a gushing fountain. I would fathom that the concept of water balloons was created by someone, first time in history, coming up with an idea of modding a balloon by filling it with water instead of air.
Essentially, mods are only the digital equivalent of house rules. House rules have existed for ages. In particularly, commonly played card games and billiard games have house rules. Perhaps the best example to use here, is Monopoly. I believe, it’s actually just a minority, who play Monopoly exactly according to the rules. One of the most common house rules, used by people, is that it is allowed to build houses on properties, before you have acquired a full colour set of the properties – have a monopoly of the city block, that is. Another quite common house rule is that the money paid by the players due to cards that they pick up, or when landing on tax squares, is placed under the Free Parking square, and when ever a player lands on Free Parkin, that player is allowed to take the money under the square. Neither of these rules are official Monopoly rules, and there are several other house rules used by the players of this game.
Monopoly even has official modifications. One can purchase, for example, Star Wars Monopoly, and Pokemon Monopoly. One of my favorite rule modifications in these is in the Pokemon Monopoly, where the rule of when you roll a pair with the dice, the result depends on the value of the pair. If you throw a pair of sixes, you can challenge another player’s property against one of your own properties. Then you both roll a dice, and if either of you get a higher value than the other, that player gets both properties. I love, how this rule brings more dynamics to this game that it otherwise quite stagnant.
For what it comes to games played by the standards 52 cards, I could guess that most of the games originate from just one original game, for which the deck was designed for. A long history of house rule “mods” have created the current plethora of games available for the deck. Yet, certainly, there are cases, where someone has just taken the deck, sat down, and designed a brand new game for it, just from scratch. Nevertheless, game mods have existed far, far before digital games, where they only have been adapted.
Modern features embracing digital game modding are not limited only to game engines and games providing a programming interfaces for modifications. Also online game stores, at least Steam provide a mechanism to distribute both game developer created official add ons (DLC) and player community provided mods (in the Workshop). Valve, the owner of Steam, has a long tradition in promoting modding. For example, Counter Strike was originally created as a modification of Valve’s game Half Life.
Outside Steam and other online stores, there are several games created by players as open source, that provide both the opportunity for anyone to join the “official” development team of the base game, as well and provide with mods to the game. I am personally most fond and familiar with Open Transport Tycoon Deluxe (OpenTTD)
I like my games moddable. I play Crusader Kings II with the Game of Thrones map, and I pick my own flavouring to RimWorld. The modern XCOM games have so many characters that I can only consider them as individuals by giving them appearances and names as close as possible of Marvel superheroes.
The problem with mods is in the testing. In the field of software engineering, the general level of quality control through proper test runs is still in a shameful state. The most professional game producers do run their unit tests and do play testing before release, but still, it is so very common to have error correcting patches arrive every month, sugar coated with new features (which then later on are discovered buggy and require further fixes). Typically, one doesn’t want to buy a new game straight up when it’s just released, but rather wait for a couple of months, until the first players have reported in the worst bugs, and the developers have released the first, crucial batches.
With mods, this is even worse. The game development team itself has a theoretical possibility to communicate and plan their designs together and see how one thing affects another. They can also build and run unit tests for the new features, and run them quite thoroughly on the systems. Mod designers are easily much less competent programmers, with no real connection to the development team, and their only interest to have some particular feature in the game so that they can play it. When there are hundreds of different mod developers creating their own mods, there is no control over A) how these mods work even on their own in different situations and settings in the games, and B) how these mods work together with other mods!
Where the joy of mods is that one can play the game of thrones in Crusader Kings II, the bane is in where suddenly one cannot suggest berothrals of their children with other rulers’ children, or the expensive hired group of mercenaries appears on another continent, without any ships, instead of next to one’s capital!
This particular mod, in it’s description even mentions that they guarantee no compatibility with any other mods. This is a common practise. Several mods list, which other mods they guarantee compatibility, and others mention, which other mods are requirements for the mod to work at all. This is tuned finest in OpenTTD, where the recent versions of the game are beginning to give already informative messages on mod conflicts, so that the player can actually identify, which mod is in conflict with which. Their earlier version only referred to often cryptic function call names that served very little help to discover, which one of the several dozens of modifications was having an error in the configuration.
What the modding world still needs, is a way for mod developers to run thorough compatibility tests of their creations, so that when a player wants to compose a nice setup of different mods, they would have some kind of table indicating, which mods are possible to use with the ones already chosen, and which mods need to be removed, if one wants to add a particular one. OpenTTD seems to be on a right track (pun intended) here, and Steam would have a good facility ready to implement such features as well.
 Andy Dyer: “PC Game Mods – From Smurfs to Counter-Strike and Beyond!” in GeForce News, 2016, https://www.geforce.com/whats-new/articles/history-of-pc-game-mods (Referenced in 10.10.2018)
 OpenTTD Team: “OpenTTD”, https://www.openttd.org/en/ (Referenced in 10.10.2018)