text: // handle collisions
  export function setupCollisionHandling(world ) {
      world.on('begin-contact', function(contact) {
          var fixtureA = contact.getFixtureA();
          var fixtureB = contact.getFixtureB();
  
          // count floor contacts
          if (fixtureA === world.explorer.footSensor || fixtureB === world.explorer.footSensor ) {
              world.explorer.numFootContacts += 1;
          }
          if (fixtureA === world.explorer.hooksense || fixtureB === world.explorer.hooksense ) {
              world.explorer.numFootContacts += 1;
          }
  
          // handle the explorer touching things
          if ( fixtureA.getBody().contactHandler !== undefined  && fixtureB.getBody() === world.explorer ) {
              fixtureA.getBody().contactHandler(world);
          }
  
          if ( fixtureB.getBody().contactHandler !== undefined  && fixtureA.getBody() === world.explorer ) {
              fixtureB.getBody().contactHandler(world);
          }
      });
  
      world.on('end-contact', function(contact) {
          var fixtureA = contact.getFixtureA();
          var fixtureB = contact.getFixtureB();
  
          // count floor contacts
          if (fixtureA === world.explorer.footSensor || fixtureB === world.explorer.footSensor ) {
              world.explorer.numFootContacts -= 1;
          }
          if (fixtureA === world.explorer.hooksense || fixtureB === world.explorer.hooksense ) {
              world.explorer.numFootContacts -= 1;
          }
      });
  }
  