diff --git a/docs/TODO b/docs/TODO
index a12fa75..198365b 100644
--- a/docs/TODO
+++ b/docs/TODO
@@ -9,13 +9,16 @@ If you see modifications to this file in git status, IGNORE them and do not comm
     - remember to periodically check the reference docs against new changes
 
 === Simulation/Physics ===
+    - IMPORTANT: for the graphical sim, we're calculating 100 physics steps per
+        frame. we need to test, and make a compromise on performance vs sim
+        accuracy, and have this set as a config constant, MAX_STEP_SIZE, with
+        a good discription nearby in the code.
     - fix moon tests with SOI coordinate transforms for planets
     - remove bodies on non closed orbits after they are a certain distance from
         the root body, or bary-center
     - add tests for each orbit type
     - add and test 'satellite' objects that should not be in parents or have a
         SOI
-    - move the example binary system config to test configs, and make some tests
 
 === Simulation Config Files ===
     - relative coordinates for child bodies