diff --git a/src/gooey.cpp b/src/gooey.cpp
index 59f8aa9..39bb5e4 100644
--- a/src/gooey.cpp
+++ b/src/gooey.cpp
@@ -41,63 +41,106 @@ gooProcessEvent(SDL_Event& e)
 		|| ImGui::GetIO().WantCaptureKeyboard);
 }
 
+void drawEllipseParameters(ellipse_parameters& ep);
+void drawGravitaationalBody(grav_body& body);
+void drawOrbitalElements(orbital_elements& el);
+void drawSatelliteWindow(satellite& sat);
+void drawSystemWindow(system_2body& sys);
+
+const static int G_WIDTH = 300;
+const static ImVec2 V_SPACER(0, 10);
+const int H_FLAGS = ImGuiTreeNodeFlags_DefaultOpen;
+
 void
-gooDraw(SDL_Window* window, orbital_elements& orbit, uint& time_step)
+gooDraw(SDL_Window* window, system_2body& sys)
 {
 	ImGui_ImplOpenGL3_NewFrame();
 	ImGui_ImplSDL2_NewFrame(window);
 	ImGui::NewFrame();
 
-	const static int w = 300;
 	int x = 0, y = 0;
 	SDL_GetWindowSize(window, &x, &y);
-	ImGui::SetNextWindowPos(ImVec2(x - w, 0));
-	ImGui::SetNextWindowSize(ImVec2(w, y));
-	ImGui::Begin("Orbital Elements");
-
-	ImGui::Text("iota, inclination:            %f", orbit.iota);
-	ImGui::Text("omega, argument of periapsis: %f", orbit.omega);
-	ImGui::Text("mu, gravitational parameter:  %f", orbit.mu);
-	ImGui::Text("nu, true anomoly: ");
-	ImGui::InputDouble("##orbit.nu", &orbit.nu, 0.1f);
-	ImGui::SameLine();
-	ImGui::Text(" radians");
-	ImGui::Spacing();
-
-	ImGui::Separator();
-	ImGui::Spacing();
-	ImGui::Text("Ellipse Parameters:");
-	ImGui::Text("semi-major axis, a:     ");
-	ImGui::InputDouble("##orbit.ep.a", &orbit.ep.a, 1000.0f);
-	ImGui::SameLine();
-	ImGui::Text(" km");
-	ImGui::Text("semi-minor axis, b:     %f km", orbit.ep.b);
-	ImGui::Text("eccentricity, e:        ");
-	ImGui::InputDouble("##orbit.ep.e", &orbit.ep.e, 0.01f);
-	ImGui::Text("linear eccentricity, c: %f km", orbit.ep.c);
-	ImGui::Spacing();
-
-	ImGui::Separator();
-	ImGui::Spacing();
-	ImGui::Text("Other Parameters");
-	ImGui::Spacing();
-	ImGui::Text("time_step:");
-	ImGui::SameLine();
-	uint step = 1;
-	ImGui::InputScalar("##other.time_step", ImGuiDataType_U32, &time_step, &step);
-	ImGui::Spacing();
-	ImGui::Text("Satellite Parameters:");
-	ImGui::Text("position:");
-	ImGui::Text("	x: %f km", orbit.pos.x);
-	ImGui::Text("	y: %f km", orbit.pos.y);
-	ImGui::Text("	z: %f km", orbit.pos.z);
-	ImGui::Text("velocity, km/s:             %f", orbit.v);
-	ImGui::Text("flight path angle:          %f", orbit.gamma);
-	ImGui::Text("epsilon, spec. orb. energy: %f", orbit.epsilon);
-	ImGui::Text("h, angular momentum:        %f", orbit.h);
+	ImGui::SetNextWindowPos(ImVec2(x - G_WIDTH, 0));
+	ImGui::SetNextWindowSize(ImVec2(G_WIDTH, y));
+	ImGui::Begin("Gooey");
+
+	drawSystemWindow(sys);
+	drawSatelliteWindow(sys.sat);
+	drawGravitaationalBody(sys.body);
+	drawOrbitalElements(sys.elements);
+	drawEllipseParameters(sys.ep);
 
 	ImGui::End();
 	ImGui::Render();
 	ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 }
 
+void drawEllipseParameters(ellipse_parameters& ep)
+{
+	if (ImGui::CollapsingHeader("Ellipse Parameters:", H_FLAGS)) {
+		ImGui::Text("semi_major axis, a:     %f km", ep.a);
+		ImGui::Text("semi_minor axis, b:     %f km", ep.b);
+		ImGui::Text("eccentricity, e:        %f   ", ep.e);
+		ImGui::Text("linear eccentricity, c: %f km", ep.c);
+		ImGui::Text("semilatus rectum, p:    %f km", ep.p);
+		ImGui::Dummy(V_SPACER);
+	}
+}
+
+void drawGravitaationalBody(grav_body& body)
+{
+	if (ImGui::CollapsingHeader("Gravitational Body:", H_FLAGS)) {
+		ImGui::Text("mu, gravitational parameter:  %f", body.mu);
+		ImGui::Text("r, radius in km:  %f           ", body.radius);
+		ImGui::Dummy(V_SPACER);
+	}
+}
+
+void drawOrbitalElements(orbital_elements& el)
+{
+	if (ImGui::CollapsingHeader("Orbital Elements", H_FLAGS)) {
+		ImGui::Text("semi_major axis, a:         %f km", el.a);
+		ImGui::Text("eccentricity, e:               %f", el.e);
+		ImGui::Text("iota, inclination:             %f", el.iota);
+		ImGui::Text("ohm, longitude ascending node: %f", el.ohm);
+		ImGui::Text("omega, argument of periapsis:  %f", el.omega);
+		ImGui::Text("nu, true anomaly at T0:        %f", el.nu);
+		ImGui::Dummy(V_SPACER);
+	}
+}
+
+void
+drawSatelliteWindow(satellite& sat)
+{
+	if (ImGui::CollapsingHeader("Satellite:", H_FLAGS)) {
+		ImGui::Text("Satellite Parameters:");
+		ImGui::Text("theta, true anomaly: %f", sat.theta);
+		ImGui::Text("r, radial distance:  %f km", sat.r);
+		ImGui::Text("position:");
+		ImGui::Text("	x: %f km", sat.position.x);
+		ImGui::Text("	y: %f km", sat.position.y);
+		ImGui::Text("	z: %f km", sat.position.z);
+		ImGui::Text("velocity, km/s:      %f", sat.v);
+		ImGui::Text("flight path angle:   %f", sat.gamma);
+		ImGui::Dummy(V_SPACER);
+	}
+
+}
+
+void drawSystemWindow(system_2body& sys)
+{
+	if (ImGui::CollapsingHeader("2 Body System:", H_FLAGS)) {
+		ImGui::Text("time_step:");
+		ImGui::SameLine();
+		uint step = 1;
+		ImGui::InputScalar("##other.time_step",
+			ImGuiDataType_U32,
+			&sys.time_step, &step
+		);
+		ImGui::Text("epsilon, spec. orb. energy: %f", sys.epsilon);
+		ImGui::Text("h, angular momentum:        %f", sys.h);
+		ImGui::Text("r_apoapsis:                 %f", sys.r_apoapsis);
+		ImGui::Text("r_periapsis:                %f", sys.r_periapsis);
+		ImGui::Dummy(V_SPACER);
+	}
+}
diff --git a/src/gooey.h b/src/gooey.h
index 781cb9a..2a7c358 100644
--- a/src/gooey.h
+++ b/src/gooey.h
@@ -16,5 +16,5 @@ bool
 gooProcessEvent(SDL_Event &e);
 
 void
-gooDraw(SDL_Window* window, orbital_elements& orbit, uint& time_step);
+gooDraw(SDL_Window* window, system_2body& sys);
 
diff --git a/src/main.cpp b/src/main.cpp
index 5949723..0b734f6 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -133,6 +133,9 @@ postFrameCallback(render_state* rs)
 	}
 
 	// TODO: will need more validation from GUI as added
+	// TODO: might be easier to preset valid ranges in gooey code see:
+	//	https://github.com/ocornut/imgui/blob/master/imgui.h#L810
+	//	^ description of IsItemDeactivatedAfterEdit();
 	if (!ellipsesEqual(c_orb.ep, g_orbit.ep)) {
 		// NOTE: handle the case where semimajor axis lowered with low
 		//	eccentricity would fail validation