Function bl

docs/tests/v2/es6/js/sanddance.js:98415–98415

      tr = item => value(item.cornerRadiusTopRight, item.cornerRadius) || 0,
      br = item => value(item.cornerRadiusBottomRight, item.cornerRadius) || 0,
      bl = item => value(item.cornerRadiusBottomLeft, item.cornerRadius) || 0,
      sz = item => value(item.size, 64),
      ts = item => item.size || 1,
      def = item => !(item.defined === false),