Example for using Elm lang to draw rays from a fixed point to the mouse location. [For Beginners]
See the demo (Start a ray by clicking the mouse.)
To run it locally:
cd elm-mouse-rays
git checkout 2015.10.30.01
elm-make src/Main.elm --output=demo.html
Then, open demo.html in your web browser.
For a walkthrough, see my blog post.