code: function checkMouseBetweenElements( that, upper, lower ) {
  			return inBetween( that.mouse.y, upper.size.top, lower.size.bottom );
  		}
docs: This method checks whether mouse-y is between the top edge of upper and bottom edge of lower.  NOTE: This method assumes that updateSize has already been called for the elements and is up-to-date.  +---------------------------- Upper -+  /-- |                                    |  | +------------------------------------+  | | ...                  | | X                   |	* Return true for mouse-y in this range * | ...                  | | +---------------------------- Lower -+  | |                                    |  | +------------------------------------+  \--