Better performance for mobile devices

I'm using some simple physics in a game, that basically involves some gravity and one projectile being shot at some targets. Yet for some reason, the game requires heavy use of the CPU of a laptop processor (30-90%). This is true even when everything is still and nothing is being shot! It works fine on a laptop but becomes slow on a tablet or phone. Is there some way to get better performance?

The GPU process and the open tab in Chrome can each take up 15% of the CPU, though it goes down if nothing has happened for a while.

Have you tried following all the steps in the performance tips bit of the manual? I found making sure I was within the suggested limits of particles made the biggest difference.

A simple game should not use much CPU. Usually this means it's doing software rendering instead of using the graphics card. Check chrome://gpu, what does it say about Canvas and WebGL? You might improve it by updating your graphics card driver.