update STYLE.md

STYLE.md

@@ -39,7 +39,7 @@ I recommend skimming over these for inspiration.
 	- open bracket `{` after that.
 	- `for`, `if`, `while`, etc. statements that only contain one line 
 - Use `/* comments */` for permanent comments, `// comments` for temporary ones e.g. `TODO`'s or notices
-- **Try to make every line 120 characters wide or less.**
+- **Try to make every line 100 characters wide or less.**
 - Start source files as `.cc` straight away, even if they're pure **C**.
 
 ### C++-specific guidelines