diff --git a/src/main.cpp b/src/main.cpp
index 5550c1f..bcb70fe 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,4 +1,19 @@
 
+/*
+ * TODO:
+ * - fix time_step and our postFrameCallback() to use time since last frame
+ *   	currently, the time step is incorrectly using 60Hz = 1s
+ *   	need to use a 'sim_timer' or something so we can track the satellite
+ *   	posistions correctly
+ * - add time to apoapsis/periapsis to satellite properties
+ * - use consistant name style for structs) 'UpperCase'
+ * - make an 'overlay' graphic for things like apoapsis, perisapsis, f1, f2,
+ *   	flight path
+ * - impulsive orbital maneuvers
+ * - Hohmman transfer orbits
+ * - patched conic method for transferring between 2 grav bodies
+ */
+
 #include <cassert>
 #include <cmath>
 
@@ -229,14 +244,14 @@ postFrameCallback(RenderState* rs, void* user_data = nullptr)
 		//updateOrbit(gs->system, ellipse_entity);
 	}
 
-		if (satellite == nullptr) {
-			RenderGroup* rg = getRenderGroupByName(rs, "manual mesh group");
-			satellite = getEntityByName(rg, "ship 01");
-		}
+	// FIXME: testing sim time
+	u64 ticks = SDL_GetTicks64();
+	static u32 last_T;
+	u32 T = ticks / 1000;
 
-		assert(satellite);
-		updateSatelliteEntity(satellite, g_sys.sat);
-		//updateOrbit(g_sys, ellipse_entity);
+	if (T != last_T) {
+		LOGF(Debug, "seconds since sim start: %d\n", T);
+		last_T = T;
 	}
 }