simtr/The-Powder-Toy — pull request #172 by china-richway2 (2013-10-11 10:02:18+00:00)
Title: Add Blocker Wall as suggested in http://powdertoy.co.uk/Discussions/Thre...

jacksonmj said a pull request may be accpeted, so I decided to send a pull request.
Suggested in http://powdertoy.co.uk/Discussions/Thread/View.html?Thread=17123