Creating Games: Add chapter

_en/games/games.md

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+---
+title: Creating Games
+layout: default
+root: ../..
+idx: 6.1
+---
+
+## Introduction
+
+The power of Minetest is the ability to easily create games without the need
+to write your own voxel graphics and algorithms or fancy networking.
+
+* [What is a Game?](#what-is-a-game)
+* [Game Directory](#game-directory)
+* [Inter-game Compatibility](#inter-game-compatibility)
+	* [API Compatibility](#api-compatibility)
+	* [Groups and Aliases](#groups-and-aliases)
+* [Your Turn](#your-turn)
+
+## What is a Game?
+
+Games are a collection of mods which work together to make a cohesive game.
+A good game has a consistent underlying theme and a direction, for example
+maybe it's a classic crafter miner with hard survival elements, or maybe
+it's a space simulation game with a steam punk automation ascetic.
+
+Game design is a complex topic, and is actually a whole field of expertise.
+It's beyond the scope of the book to more than briefly touch on it.
+
+## Game Directory
+
+The structure and location of a game will seem rather familiar after working
+with mods.
+Games are found in a game location such as `minetest/games/<foo_game>`.
+
+	foo_game
+	├── game.conf
+	├── menu
+	│   ├── header.png
+	│   ├── background.png
+	│   └── icon.png
+	├── minetest.conf
+	├── mods
+	│   └── ... mods
+	├── README.txt
+	└── settingtypes.txt
+
+The only thing that is required is a mods folder, but `game.conf` and `menu/icon.png`
+are recommended.
+
+## Inter-game Compatibility
+
+### API Compatibility
+
+It's a good idea to try to keep as much API compatibility with Minetest Game as
+convenient, as it'll make porting mods to another game much easier.
+
+API compatibility is the sum of the following things:
+
+* Lua API table - All documented/advertised functions in the global table which shares the same name.
+		For example, `mobs.register_mob`.
+* Registered Nodes/Items - The presence of items.
+
+It's probably fine to have partial breakages as long as 90% of dependency
+usecases still works. For example, not having a random utility function that was
+only actually used internally is ok, but not having `mobs.register_mobs` is bad.
+
+The best way to keep compatibility with another game is to keep API compatibility
+with any mods which have the same name.
+That is, if a mod uses the same name as another mod even if third party,
+then it should have a compatible API.
+For example, if a game includes a mod called `doors` then it should have the
+same API as `doors` in Minetest Game.
+
+It's difficult to maintain API compatibility with a disgusting God mega-mod like
+*default* in Minetest Game, in which case the game shouldn't include a mod named
+default.
+
+API compatibility also applies to other third-party mods and games,
+so try to make sure that any new mods have a unique mod name.
+To check whether a mod name has been taken, search for it on
+[content.minetest.net](https://content.minetest.net/).
+
+### Groups and Aliases
+
+Groups and Aliases are both massive tools in keeping compatibility between games,
+as it allows item names to be different between different games. Common nodes
+like stone and wood should have groups to indicate the material. It's also a
+good idea to provide aliases from default nodes to any direct replacements.
+
+## Your Turn
+
+* Make a game - It can be simple, if you like.

_en/quality/clean_arch.md

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 title: Intro to Clean Architectures
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 ## Introduction

_en/quality/common_mistakes.md

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_en/quality/luacheck.md

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_en/quality/readmore.md

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_en/quality/releasing.md

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_en/quality/security.md

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_en/quality/unit_testing.md

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 title: Automatic Unit Testing
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 ## Introduction