update README

Author: spamegg1

README.md

@@ -2,7 +2,14 @@
 
 ![world](images/world.png)
 
-Attempting to recreate Barwise and Etchemendy's [Tarski's world](https://www.gradegrinder.net/Products/tw-index.html) in [Doodle's Reactor](https://github.com/creativescala/doodle) using [Scala 3](https://www.scala-lang.org).
+Attempting to recreate Barwise and Etchemendy's
+[Tarski's world](https://www.gradegrinder.net/Products/tw-index.html) in
+[Doodle's Reactor](https://github.com/creativescala/doodle) using
+[Scala 3](https://www.scala-lang.org).
+
+They use 3D objects (like cube, tetrahedron, dodecahedron etc.) but I'm going with 2D as in
+[Susanna Epp's Discrete Math book](https://github.com/spamegg1/Epp-Discrete-Math-5th-solutions/).
+The image above is taken from there.
 
 ## Info