Racetrack in <a href="https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life" class="extiw" title="en:Conway's Game of Life">Conway's Game of Life</a>. Created string of images in Java, then processed string to add colour.
<p>Multiple low-level structures interact to allow one structure to "race" along a closed track. The racer starts as a <a href="https://en.wikipedia.org/wiki/Glider_(Conway%27s_Life)" class="extiw" title="en:Glider (Conway's Life)">glider</a> in the diagonal column to the right of the main pattern. It is then reflected multiple times along the track. At the bottom it is temporarily transformed into a <a href="https://en.wikipedia.org/wiki/Spaceship_(cellular_automaton)" class="extiw" title="en:Spaceship (cellular automaton)">spaceship</a>. It then finishes the track as a glider again.
Legend :
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<ul><li>Green structure : <a href="https://en.wikipedia.org/wiki/Gun_(cellular_automaton)" class="extiw" title="en:Gun (cellular automaton)">Gun</a></li>
<li>Yellow structure : <a href="https://en.wikipedia.org/wiki/Glider_(Conway%27s_Life)" class="extiw" title="en:Glider (Conway's Life)">Glider</a></li>
<li>Red structure : <a href="https://en.wikipedia.org/wiki/Spaceship_(cellular_automaton)" class="extiw" title="en:Spaceship (cellular automaton)">Spaceship</a></li>
<li>Violet structure : <a href="https://en.wikipedia.org/wiki/Reflector_(cellular_automaton)" class="extiw" title="en:Reflector (cellular automaton)">Reflector</a></li>
<li>Blue structure : <a href="https://en.wikipedia.org/wiki/Still_life_(cellular_automaton)#Eaters_and_reflectors" class="extiw" title="en:Still life (cellular automaton)">Eaters</a> (both as still lives and oscillators) and others still lives.</li></ul>
<a href="https://en.wikipedia.org/wiki/User:Simpsons_contributor" class="extiw" title="en:User:Simpsons contributor">Simpsons contributor</a> (<a href="https://en.wikipedia.org/wiki/User_talk:Simpsons_contributor" class="extiw" title="en:User talk:Simpsons contributor">talk</a>)
<span class="int-own-work" lang="en">Own work</span> (<span lang="en" dir="ltr">Original text: <i><bdi lang="">I created this work entirely by myself.</bdi></i></span>)