Player accessibility improvements

[FrenjaminBanklin]

• The controls for the drawn graph (zooming and panning) don't seem to be reachable via the tab key.
  • Neither are the instructions, or the equation text.
• Need to determine whether it's even possible to interpret the generated mathematical equations or the resulting line charts with a screen reader. Perhaps have an alternative that will read out a y value for a given x value according to the provided equation, especially if we find some way of making the equations compatible with screen readers.