README.md in rsyntaxtree-1.2.10 vs README.md in rsyntaxtree-1.2.12

- old
+ new

@@ -1,8 +1,8 @@
 <img src='https://github.com/yohasebe/rsyntaxtree/blob/master/img/rsyntaxtree.png?raw=true' style='width: 256px;' />
 
-**RSyntaxTree** is a graphical syntax tree generator written in the Ruby programming language. 
+**RSyntaxTree** is a graphical syntax tree generator for linguistic research 
 
 ## Documentation
 
 Documentation is currently available in the following languages:
 
@@ -55,9 +55,11 @@
 <img src='https://github.com/yohasebe/rsyntaxtree/blob/master/img/sample.png?raw=true' width='600' />
 
 ## Installation
 
 `# gem install rsyntaxtree`
+
+**NOTE**: Currently, installation of the gem package on macOS is not recommended. Please use the [Docker image](https://hub.docker.com/r/yohasebe/rsyntaxtree) or the [web interface](https://yohasebe.com/rsyntaxtree).
 
 ## Usage
 
 For the web interface, see Usage section of <https://yohasebe.com/rsyntaxtree>.
 