diff --git a/OrbSim2/README.txt b/OrbSim2/README.txt
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--- a/OrbSim2/README.txt
+++ b/OrbSim2/README.txt
@@ -1,4 +1,4 @@
-A numerical simulation of n-body newtonian gravity in 3d.
+A numerical simulation of n-body newtonian gravity in 2d. Precursor to OrbSim2-3d, which lives in its own repo.
 Can be used to simulate actual physical systems, and also to make some interesting-looking animations of a large number of bodies interacting.
 Based off of some of the work from BallisticSim and OrbitalSim, uses 3rd order explicit Adams-Bashford method for numerical integration.
 Much faster than the earlier simulators.