Made it possible to set corner radius and button inset on the accordion box, started using it in Under Pressure simulation, see https://github.com/phetsims/under-pressure/issues/17
Made it possible to set corner radius and button inset on the accordion box, started using it in Under Pressure simulation, see https://github.com/phetsims/under-pressure/issues/17

phetsims/sun,phetsims/sun,phetsims/sun