Can't tell if you're doing something wrong without seeing the code, but in general, Processing.js is slower than processing, and Processing.js on a phone is slower than on a desktop.

Thanks for your answer. I linked to the current build in the first post, but here it is again. All the source code is there. I do understand that processing.js on mobile is slower, but if it's this slow does that mean it's just unusable?

If you can maintain a framerate of 24, that's useable.  There are things you can do to improve your framerate.

Thanks! That all makes a lot of sense. The only thing I'm unsure about is 1. I had come to the same conclusion earlier, but when I took out the interface the foreground animation began ghosting since you could see the previous frames. How do you draw the background once but still have the previous frames of the foreground elements clear?

Try 

I was going to suggest: Don't use background. Draw a solid rectangle in the "game play" area (that doesn't fill the entire window). But leave the "interface" area alone (e.g. draw it once and redraw it only when it's being interacted with).

Thanks guys! So far background(0,0) is working really well. I really like the idea of using alpha and just switching the canvas background using jQuery. I haven't done any benchmarks for the new engine yet, but when I do I will probably switch to fil(0,0) and use rect to minimize the active redraw area. Thanks so much! :)

So, I tried doing fill(0,0) and drawing a solid rectangle in order to only clear what needed to be cleared, but it doesn't seem to work. After looking at the processing.js core, it looks like there is no clearRect function being used inside rect (it is however being used in background, which is why it worked there). I am trying to add it to the core, but haven't had any success so far. Would it be smarter to try and write a clearRect function in the pde itself? Is this a known issue with processing.js?

i bet if you write it in javascript directly rather than going through the processing.js library it will be much faster