README improvements

README.md

@@ -137,6 +137,35 @@ Various approaches exist to writing your own client, but in general:
 * Refer to the provided HTML/JS interface for a reference
 * Let me know if you get stuck, I'm happy to help!
 
+### Structure of the source code
+
+To navigate your way around the source code, this list may help.
+
+*Python back-end code*
+
+* `/core` - Core classes and scripts
+* `/data` - Data storage classes
+* `/providers` - Classes providing data by accessing the APIs of other services
+* `/server` - Classes for running Spothole's own web server
+
+*Templates*
+
+* `/views` - Templates used for constructing Spothole's user-targeted HTML pages
+
+*HTML/JS/CSS front-end code*
+
+* `/webassets` - Root for static files served by the web server
+* `/webassets/apidocs` - Contains the OpenAPI spec (`openapi.yml`)
+* `/webassets/css` - CSS files used by the web front-end
+* `/webassets/fa` - a copy of the FontAwesome library
+* `/webassets/img` - image files used by the web front-end
+* `/webassets/js` - JavaScript used by the web front-end
+
+*Miscellaneous*
+
+* `/` - Main script (`spothole.py`), pip `requirements.txt`, config, README, etc.
+* `/images` - Image sources
+
 ### Extending the server
 
 Spothole is designed to be easily extensible. If you want to write your own provider, simply add a module to the `providers` package containing your class. (Currently, in order to be loaded correctly, the module (file) name should be the same as the class name, but lower case.)