I was curious about whether it would be possible to draw a circle (in html / canvas), without any float parameter (PI). I am not sure what mobile devices support float arithmetic FPU (without it, float is slow emulated, with integer arithmetic ALU). Also, even with a CPU with FPU, maybe integer arithmetic (with ALU) could use less battery?
For instance, in the code for arc, parameter Math.PI can not be avoided:
context.arc(centerX, centerY, radius, 0, 2 * Math.PI);