Site doesn't work on mobile devices.

[Spirko]

I love ManyTinyThings and look forward to using it to enlighten my physics students.

Currently ManyTinyThings.github.io doesn't work on mobile devices. Fixing this isn't too difficult:

• Change the mouse events on the Canvas elements to pointer events. This can be done by just changing the first argument to the *.addEventListener() calls. "mousedown" becomes "pointerdown", etc. Since PointerEvent is derived from MouseEvent, the handler code still works.
• Update the style of the simulation canvas elements to include touch-action: none; or maybe touch-action: pinch-zoom;. This prevents the browser from intercepting the pointer events for scrolling of the page. (As a side effect, the user has to scroll by dragging from outside the canvas.)

-Jeff