Please see inside. A demonstration of how it is possible to map coordinates (x,y) into the tempo variable, and then decode it back into x and y. Hopefully this will prove to be invaluable when it comes to removing as many variables as I can from my platformer. There are no tricks on this, the x and y variables are reset to 0 to prove that they are only getting their information from the tempo variable.
All code by me. Thanks to @GarboMuffin for the idea to use the music extension for "tempo"rary storage. NOTE: It works only for x (-360 to 360) and y (-270 to 270) If you try numbers outside of this range, you might not get the numbers you wanted. Accuracy is limited to two decimal places. (There is a limit to how many this can support because JavaScript's safe integer limit is 53 bits.) I multiplied the stage boundaries by 1.5 to give them a little bit of leg room, but in hindsight it might be a bit over. The fact that I wasted an hour of my life to create this conversion that is useful for almost nobody is crazy.