You can find original C++ source code (and excellent article about galaxy simulation) on
If you want to contact me please use my twitter handle: @hipokamp. I plan to update the code so follow me if you are interested.
2015-08-20 - Update: Bit of cleanup, WebGL version use single vertex buffer now, experimental GLSL version (vertex shader based)
You can change canvas size (try different ratio, for example 800x400 with WebGL renderer for nice pseudo-3d effect).
Canvas renderer is just for testing/debugging - it is sloooooow (slideshow performance for 5K stars on my Mid2011 MacBook Air) and result isn't as nice as WebGL (but I am working on it...).
Time step size controls how much time will pass with each frame (note - it takes thousands of years to move a star in the space ;)). Make it bigger to see how colors change with age - quite nice effect.
Too much stars on too small canvas will not look nice :). Make the canvas bigger to get better effect.
Animation performance: my MacBook Air with WebGL renderer can handle 15K stars quite nice but above that performance drops to slideshow...