LostCity.xml

<sequence values="BWRDIE">
  <one in="B" out="I" steps="4" comment="make a few lakes by random growth"/>
  <one in="IB" out="*I" steps="24000"/>
  <convolution neighborhood="Moore">
    <rule in="I" out="B" sum="5..8" values="B"/>
    <rule in="B" out="I" sum="5..8" values="I"/>
  </convolution>

  <one in="B" out="R" steps="20" comment="make some land by a self-avoiding random walk with backtracking"/>
  <markov>
    <all in="RBB" out="WWR"/>
    <all in="RWW" out="DDR"/>
  </markov>
  <all in="R" out="D"/>

  <one in="BBWBB" out="**B**" comment="erode narrow sections of land"/>  
  <all>
    <rule in="IW" out="*D"/>
    <rule in="I*/*W" out="**/*D"/>
    <rule in="DW" out="*D"/>
  </all>
  <prl in="D" out="B"/>

  <prl steps="2">
    <rule in="WB" out="*D"/>
    <rule in="DB" out="*D" p="0.5"/>
  </prl>
  <convolution neighborhood="Moore">
    <rule in="D" out="B" sum="5..8" values="B"/>
    <rule in="B" out="D" sum="5..8" values="DI"/>
  </convolution>

  <one in="BB*/BBB/*B*" out="***/*E*/***"/>
  <all in="*E*/EBE" out="***/*E*"/>
  <prl in="D" out="B"/>
</sequence>

<!--
Based on the model by Andrew Kay https://github.com/kaya3/pattern-match-2d
-->