!YS-v0

defn main():
  each line generate(10 '_###_##_#_#_#_#__#__'):
    say: line

defn generate(n cells):
  when n.?:
    cons cells:
      generate n.--:
        loop cs cells, ncs subs(cells 0 1):
          if cs.# >= 3:
            recur cs.subs(1):
              ncs +:
                filter(\(_:S == '#') cs.subs(0 3))
                  .#.eq(2).if('#' '_')
            else: ncs + cs.subs(1)