anchor.diff:          {wheredim,
               {wherevar, "A", [
               {"A", {'if',
  -                    [{lte({'#', TimeD}, 0), "B"}],
  +                    lte({'#', TimeD}, 0),
  +                    "B",
                       {'@',
                           plus({'@', "A", {t, [{SpaceD,      times({'#', SpaceD}, 2    )}]}},
                                {'@', "A", {t, [{SpaceD, plus(times({'#', SpaceD}, 2), 1)}]}}),
  
positive.code:                                 {t, [{TimeD, minus({'#', TimeD}, 1)}]}}}},
                      {"X1",
                          {'if',
                              [{tand(tand(gte({'#', XD}, 1), lte({'#', YD}, 1024)),
                                     tand(gte({'#', YD}, 1), lte({'#', YD}, 1024))),
                                {'#', XD}}],
                              1}}
                  ]},
              [{TimeD,2}, {XD,0}, {YD,0}]},
  
negative.code:                 [
                      {"N0",
                          {'if',
                              eq({'#', TimeD}, 0),
                              "N1",
                              {'@', "N0",
                                  {t, [{TimeD, minus({'#', TimeD}, 1)}]}}}},
                      {"N1",
                          {'if',
                              eq({'#', SpaceD}, 0),
                              1,
                              times({'@', "N1", {t, [{SpaceD, minus({'#', SpaceD}, 1)}]}}
                                  , 2)
                          }}
  