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+## Environment variables
+
+#### Xash3D FWGS
+
+The engine respects these environment variables:
+
+| Variable              | Type       | Description |
+| --------------------- | ---------- | ----------- |
+| `XASH3D_GAME`         | _string_   | Overrides default game directory. Ignored if `-game` command line argument is set |
+| `XASH3D_BASEDIR`      | _string_   | Sets path to base (root) directory, instead of current working directory |
+| `XASH3D_RODIR`        | _string_   | Sets path to read-only base (root) directory. Ignored if `-rodir` command line argument is set |
+| `XASH3D_EXTRAS_PAK1`  | _string_   | Archive file from specified path will be added to virtual filesystem search path in the lowest possible priority |
+| `XASH3D_EXTRAS_PAK2`  | _string_   | Similar to `XASH3D_EXTRAS_PAK1` but next to it in priority list |
+
+Environment variables NOT listed in the table above are used internally, and aren't considered as stable interface.
+
+#### mdldec
+
+| Variable              | Type       | Description |
+| --------------------- | ---------- | ----------- |
+| `MDLDEC_ACT_PATH`     | _string_   | If set, will read activities list from this path |