All the folders must be present, do not delete any folders. Many files include headerfiles from other folders.
The current simulations will work only in the presence of these header files. Do not use any other updated version of the files (for header files from PHET) to run the simulations. There is a lot of change in the newer versions that are not compatible with the current simulations. Hence do not clone the git repos for the old files.

RollerCoaster: ./rollercoaster/
Compost Simulation: ./compost/
Pulley Simulation: ./pulley/
Inclined Plane: ./inclined-plane/

Instructions to run the code:
1. Download and install git
2. Download & install node+npm from http://nodejs.org/download
3. Launch a node server program on your development machine
	a. Install the http-server as a command line program. Use a different command prompt than the one above since the one above will not have the new path for npm. 

npm install http-server -g

b. Change into the phetsims directory (if you were not already there).
cd phetsims/

c. Run the http server program
http-server

4. Open a browser to the path for one of the simulations:
http://localhost:8080/rollercoaster/rollercoaster_en.html

For building the code: (developing the HTML output file)
1. cd phetsims/rollercoaster
2. grunt --force

Refer PhETDevelopmentOverview.pdf for specific details