Add first draft of the README

README.md

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+# git-hydra
+
+**git-hydra** (working title) is an open-source game about learning Git!
+
+The current form is an early prototype, and will change significantly until the end of February 2021.
+
+## Play the game!
+
+You can download binaries of the game here:
+
+- [Linux](https://git-learning-game.github.io/git-hydra/linux/git-hydra.zip)
+- [macOS](https://git-learning-game.github.io/git-hydra/mac/git-hydra.zip)
+
+We'll also have a Windows version soon – stay tuned! :)
+
+## Report bugs!
+
+If something doesn't work or looks broken, please let us know! You can describe the issue you're having [in our issue tracker](https://github.com/git-learning-game/git-hydra/issues).
+
+If you have ideas for new features, we'd be excited to hear them! Also in that case, we invite you to [open an issue](https://github.com/git-learning-game/git-hydra/issues)!
+
+## Build your own level!
+
+Wanna build your own level? Great! Here's how to do it:
+
+1. Download the latest version of the [Godot game engine](https://godotengine.org).
+1. Clone this repository.
+1. Run the game – the easiest way to do so is to run `godot main.tscn` from the project directory.
+1. Get a bit familiar with the levels which are currently there.
+1. Take a look into the `levels` directory. It's split into chapters, and each level is a file.
+1. Make a copy of an existing level or start writing your own. See the documention of the format below. Put your level in the `contrib` chapter.
+1. The dropdowns in the game will automatically refresh to contain your level, you don't need to restart the game.
+1. Write and test your level. If you're happy with it, feel free to send it to us in a pull request! <3
+
+### Level format
+
+```
+[description]
+
+This text will be shown when the level starts.
+
+It describes the task or puzzle the player can solve.
+
+[congrats]
+
+This text will be shown after the player has solved the level.
+
+Can contain additional information, or bonus exercises.
+
+[setup]
+
+# Bash commands that set up the initial state of the level. An initial
+# `git init` is always done automatically. The default branch is called `main`.
+
+echo You > people_who_are_awesome
+git add .
+git commit -m "Initial commit"
+
+[win]
+
+# Bash commands that check whether the level is solved. Write these as if you're
+# writing the body of a Bash function. Make the function return 0 if it's
+# solved, and a non-zero value otherwise. You can use `return`, and also, Bash
+# functions return the exit code of the last statement, which sometimes allows
+# very succinct checks.
+
+# Check whether the file has at least two lines in the latest commit:
+test "$(git show HEAD:people_who_are_awesome | wc -l)" -ge 2
+```
+
+A level can consist of multiple repositories. To have more than one, you can use sections like `[setup <name>]` and `[win <name>]`, where `<name>` is the name of the remote. The default name is "yours". All repositories will add each other as remotes. Refer to the *experiments/pull-merge-push* level for an example.
+
+### Level guidelines
+
+At this stage, we're still exploring ourselves which kind of levels would be fun! So feel free to try new things: basic introductions with a little story? Really hard puzzles? Levels where you have to find information? Levels where you need to fix a problem? Levels with three remotes?
+
+## Contributing code
+
+Feel free to make improvements to the code and send pull requests! There is one exception: because merge conflicts in Godot's scene files tends to be hard to resolve, before working on an existing *\*.tscn* file, please get in touch with us.
+
+## Code of Conduct
+
+We have a [Code of Conduct](CODE_OF_CONDUCT.md) in place that applies to all project contributions, including issues and pull requests.
+
+## Funded by
+
+<a href="https://www.bmbf.de/en/"><img src="https://timelens.io/assets/images/bmbf.svg" alt="Logo of the German Ministry for Education and Research" height="100px"></a>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <a href="https://prototypefund.de/en/"><img src="https://timelens.io/assets/images/prototypefund.svg" alt="Logo of the Prototype Fund" height="100px"></a>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <a href="https://okfn.de/en/"><img src="https://timelens.io/assets/images/okfde.svg" alt="Logo of the Open Knowledge Foundation Germany" height="100px"></a>
+
+## License
+
+TBD