=== J1 [Insert "x"]

     xo
       \
        o      xo
         \     /
         xo  xo
           \ /
            o
           /
          @

===================== J2 [Collect "x"]

     xo
       \
        o      xo
         \     /
          o   o
           \ /
            o
           /
         x@

===================== J1 [Delete "((x))"]

          o
           \
            o
           /
         x@

===================== I2 [Refold "(())"]

          x
          @

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