Visit http://jiyinyiyong.github.com/clew-maker/page/ to see the demo.
Make sure you are using a browser rendering webkit engine.
By default, it will show a randon curve, which doesn't writes in localStorage.
As you clicks the numbers on the right, you can choose a point to edit.
After the number's row turns to blue, just move your mouse on the SVG.
Click on the SVG to save that point. But as the mouse moves, it changes dependently.
localstorage.memory saves the positions of all points.
Some docs about SVG:
http://www.w3.org/TR/SVG/paths.html
https://developer.mozilla.org/en-US/docs/SVG/Tutorial/Paths
http://www.w3schools.com/svg/svg_path.asp
http://www.learnsvg.com/books/learnsvg/html/bitmap/chapter04/page04-1.php