diff --git a/lib/skein/src/particlemap.cpp b/lib/skein/src/particlemap.cpp
index b0320e8..ce6633e 100644
--- a/lib/skein/src/particlemap.cpp
+++ b/lib/skein/src/particlemap.cpp
@@ -119,7 +119,14 @@ void ParticleMap::setParticleLocalVelocity(const std::string& id, double time, c
     newOrbit.setTrueAnomaly(keplerian[astro::trueAnomalyIndex]);
 
     const double newMeanAnomaly = newOrbit.getMeanAnomaly(gravitationalParameter, time);
-    const double newMeanAnomalyAtEpoch = originalMeanAnomalyAtEpoch - (newMeanAnomaly - originalMeanAnomaly);
+    const double meanAnomalyShift = newMeanAnomaly - originalMeanAnomaly;
+    const double periapsisShift = newOrbit.getArgumentOfPeriapsis() - orbit.getArgumentOfPeriapsis();
+    //const double ascendingNodeShift = newOrbit.getLongitudeOfAscendingNode() - orbit.getLongitudeOfAscendingNode();
+
+    const double newMeanAnomalyAtEpoch = originalMeanAnomalyAtEpoch
+        - meanAnomalyShift
+        - periapsisShift;
+        //- ascendingNodeShift;
     newOrbit.setMeanAnomalyAtEpoch(newMeanAnomalyAtEpoch);
 
     setRelationship(parentId, id, newOrbit);
diff --git a/src/main.cpp b/src/main.cpp
index 93a5e45..c4aab42 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -35,7 +35,8 @@
 struct Input
 {
     bool pauseTime;
-    bool updateOrbit;
+    bool prograde;
+    bool retrograde;
 } input;
 
 
@@ -44,14 +45,16 @@ void keyCallback(GLFWwindow* window, int key, int scancode, int action, int mods
     if (action == GLFW_PRESS)
     {
         input.pauseTime = key == GLFW_KEY_SPACE;
-        input.updateOrbit = key == GLFW_KEY_W;
+        input.prograde = key == GLFW_KEY_W;
+        input.retrograde = key == GLFW_KEY_S;
     }
 }
 
 void clearInput()
 {
     input.pauseTime = false;
-    input.updateOrbit = false;
+    input.prograde = false;
+    input.retrograde = false;
 }
 
 // now should always increase linearly with real world time, this should not be modified by input
@@ -88,36 +91,43 @@ int main()
 
     // set parameters of moon's orbit around earth
     Orbit moonOrbit;
-    double moonOrbitSemiMajorAxis =  3.84748e8;
+    //double moonOrbitSemiMajorAxis =  3.84748e8;
+    double moonOrbitSemiMajorAxis =  1;
     moonOrbit.setSemiMajorAxis(moonOrbitSemiMajorAxis); // metres
-    moonOrbit.setEccentricity(0.055);
-    moonOrbit.setInclination(glm::radians(5.15));       // radians
-    moonOrbit.setArgumentOfPeriapsis(318.15);           // in the case of the moon these last two values are
-    moonOrbit.setLongitudeOfAscendingNode(60.0);        // pretty much constantly changing so use whatever
+    //moonOrbit.setEccentricity(0.055);
+    //moonOrbit.setInclination(glm::radians(5.15));       // radians
+    //moonOrbit.setArgumentOfPeriapsis(318.15);           // in the case of the moon these last two values are
+    //moonOrbit.setLongitudeOfAscendingNode(60.0);        // pretty much constantly changing so use whatever
+    moonOrbit.setEccentricity(0.01);
+    moonOrbit.setInclination(0.0);
+    moonOrbit.setArgumentOfPeriapsis(0.0);
+    moonOrbit.setLongitudeOfAscendingNode(0.0);
     moonOrbit.setTrueAnomaly(0.0);
 
     // set parameters of satellite orbit around moon
-    Orbit stationOrbit;
-    stationOrbit.setSemiMajorAxis(5e7);
-    stationOrbit.setEccentricity(0.6);
-    stationOrbit.setInclination(glm::radians(89.0));
-    stationOrbit.setArgumentOfPeriapsis(43.2);
-    stationOrbit.setLongitudeOfAscendingNode(239.7);
-    stationOrbit.setTrueAnomaly(0.0);
+    //Orbit stationOrbit;
+    //stationOrbit.setSemiMajorAxis(5e7);
+    //stationOrbit.setEccentricity(0.6);
+    //stationOrbit.setInclination(glm::radians(89.0));
+    //stationOrbit.setArgumentOfPeriapsis(43.2);
+    //stationOrbit.setLongitudeOfAscendingNode(239.7);
+    //stationOrbit.setTrueAnomaly(0.0);
 
     ParticleMap map;
-    map.setParticle({"earth", 5.9e24});
-    map.setParticle({"moon", 7.3e22});
-    map.setParticle({"station", 1e6});
+    //map.setParticle({"earth", 5.9e24});
+    //map.setParticle({"moon", 7.3e22});
+    map.setParticle({"earth", 1});
+    map.setParticle({"moon", .5});
+    //map.setParticle({"station", 1e6});
     map.setRelationship("earth", "moon", moonOrbit);
-    map.setRelationship("moon", "station", stationOrbit);
+    //map.setRelationship("moon", "station", stationOrbit);
 
     float scale = moonOrbitSemiMajorAxis * 1.1;
     ParticleVisualizer earthVis(map, "earth", 0.1, litProgram, unlitProgram, scale);
     ParticleVisualizer moonVis(map, "moon", 0.02, litProgram, unlitProgram, scale);
-    ParticleVisualizer stationVis(map, "station", 0.01, litProgram, unlitProgram, scale);
+    //ParticleVisualizer stationVis(map, "station", 0.01, litProgram, unlitProgram, scale);
     OrbitVisualizer moonOrbitVis(map, "moon", unlitProgram, scale);
-    OrbitVisualizer stationOrbitVis(map, "station", unlitProgram, scale);
+    //OrbitVisualizer stationOrbitVis(map, "station", unlitProgram, scale);
 
     // register input
     glfwSetKeyCallback(window, keyCallback);
@@ -166,16 +176,18 @@ int main()
         }
         else
         {
-            if (input.updateOrbit)
+            //glm::dvec3 v = map.getParticleLocalVelocity("station", time);
+            glm::dvec3 v = map.getParticleLocalVelocity("moon", time);
+            if (input.prograde)
             {
-
-                const glm::dvec3 p = map.getParticleLocalPosition("station", time);
-
-                const glm::dvec3 v = map.getParticleLocalVelocity("station", time);
-                const glm::dvec3 newVelocity = v * 0.99;
-
-                map.setParticleLocalVelocity("station", time, newVelocity);
+                v *= 1.01;
             }
+            else if (input.retrograde)
+            {
+                v *= 0.99;
+            }
+            //map.setParticleLocalVelocity("station", time, v);
+            map.setParticleLocalVelocity("moon", time, v);
         }
 
         // rendering
@@ -186,17 +198,17 @@ int main()
         const Particle& earth = map.getParticle("earth");
         const Particle& moon = map.getParticle("moon");
         moonOrbit = map.getOrbit("moon");
-        stationOrbit = map.getOrbit("station");
+        //stationOrbit = map.getOrbit("station");
         moonOrbit.update(time, earth.getGravitationalParameter());
-        stationOrbit.update(time, moon.getGravitationalParameter());
+        //stationOrbit.update(time, moon.getGravitationalParameter());
         map.setRelationship("earth", "moon", moonOrbit);
-        map.setRelationship("moon", "station", stationOrbit);
+        //map.setRelationship("moon", "station", stationOrbit);
 
         earthVis.render(time);
         moonVis.render(time);
-        stationVis.render(time);
+        //stationVis.render(time);
         moonOrbitVis.render(time);
-        stationOrbitVis.render(time);
+        //stationOrbitVis.render(time);
 
         glfwSwapBuffers(window);
     }