🐐 Compound assignment

README.md

@@ -22,6 +22,18 @@ Variables are set with the `DESIGNA` and `VT` keywords. Type is inferred.
 
 Variable can consist of lower-case letters, numbers, as well as `_`.
 
+### Compound assignment
+
+`AVGE` (+=) and `MINVE` (-=) are shorthand for incrementing or decrementing a variable:
+
+![Compound assignment](snippets/compound.png)
+
+```
+> VIII
+```
+
+`x AVGE III` is equivalent to `DESIGNA x VT x + III`.
+
 ## Data types
 ### NVLLVS
 `NVLLVS` is a special kind of data type in `CENTVRION`, similar to the `null` value in many other languages. `NVLLVS` can be 0 if evaluated as an int or float, or an empty string if evaluated as a string. `NVLLVS` cannot be evaluated as a boolean.