diff --git a/core/src/sagittarius/model/Moon.java b/core/src/sagittarius/model/Moon.java
index 51b92df..8573b44 100644
--- a/core/src/sagittarius/model/Moon.java
+++ b/core/src/sagittarius/model/Moon.java
@@ -1,6 +1,9 @@
 package sagittarius.model;
 
+import javax.print.attribute.standard.PrinterLocation;
+
 import com.badlogic.gdx.graphics.Color;
+import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 import com.badlogic.gdx.math.MathUtils;
 import com.badlogic.gdx.math.Vector2;
 
@@ -21,12 +24,9 @@ public class Moon extends Planet {
 
     @Override
     public void act(float dt) {
-
         this.rotateBy(10.0f / this.altitude);
-
         this.setX(sun.getX() + this.altitude*MathUtils.cosDeg(this.getRotation()));
         this.setY(sun.getY() + this.altitude*MathUtils.sinDeg(this.getRotation()));
-
     }
 
     /**
diff --git a/core/src/sagittarius/model/MouseInfo.java b/core/src/sagittarius/model/MouseInfo.java
index 20b67f0..1793788 100644
--- a/core/src/sagittarius/model/MouseInfo.java
+++ b/core/src/sagittarius/model/MouseInfo.java
@@ -1,11 +1,9 @@
 package sagittarius.model;
 
-import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.graphics.g2d.Batch;
 import com.badlogic.gdx.graphics.g2d.BitmapFont;
 import com.badlogic.gdx.scenes.scene2d.Actor;
 
-import sagittarius.SagittariusGame;
 import sagittarius.view.GameScreen;
 
 public class MouseInfo extends Actor {
@@ -22,10 +20,10 @@ public class MouseInfo extends Actor {
 
         font.draw(batch, "screen=" + (int)GameScreen.screenCursor.x + "," + (int)GameScreen.screenCursor.y,
             GameScreen.worldCursor.x, GameScreen.worldCursor.y + font.getCapHeight());
-        
+
         font.draw(batch, "world=" + (int)GameScreen.worldCursor.x + "," + (int)GameScreen.worldCursor.y,
             GameScreen.worldCursor.x, GameScreen.worldCursor.y + font.getCapHeight()*2);
-    
+
     }
 
 }
diff --git a/core/src/sagittarius/model/Planet.java b/core/src/sagittarius/model/Planet.java
index 4f379d0..e768df0 100644
--- a/core/src/sagittarius/model/Planet.java
+++ b/core/src/sagittarius/model/Planet.java
@@ -5,9 +5,9 @@ import com.badlogic.gdx.graphics.g2d.Batch;
 import com.badlogic.gdx.graphics.g2d.BitmapFont;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 import com.badlogic.gdx.math.Vector2;
-import com.badlogic.gdx.scenes.scene2d.Actor;
+import com.badlogic.gdx.scenes.scene2d.Group;
 
-public class Planet extends Actor {
+public class Planet extends Group {
 
 // ---------- ATTRIBUTEs ----------
 
@@ -33,6 +33,7 @@ public class Planet extends Actor {
         fontDebug.draw(batch, "radius=" + (int)radius, getX(), getY() + fontDebug.getCapHeight()*2);
         fontDebug.draw(batch, "mass=" + (int)mass, getX(), getY() + fontDebug.getCapHeight());
         fontDebug.draw(batch, "pos=" + (int)getX() + "," + (int)getY(), getX(), getY());
+        drawChildren(batch, parentAlpha);
     }
 
     @Override
@@ -40,6 +41,7 @@ public class Planet extends Actor {
         super.drawDebug(shapes);
         shapes.setColor(this.getColor());
         shapes.circle(this.getX(), this.getY(), this.radius);
+        drawDebugChildren(shapes);
     }
 
     /**
@@ -49,4 +51,8 @@ public class Planet extends Actor {
         return this.radius;
     }
 
+    public void addMoon(Moon moon) {
+        this.addActor(moon);
+    }
+
 }
diff --git a/core/src/sagittarius/view/GameScreen.java b/core/src/sagittarius/view/GameScreen.java
index 7390d90..b0671aa 100644
--- a/core/src/sagittarius/view/GameScreen.java
+++ b/core/src/sagittarius/view/GameScreen.java
@@ -4,6 +4,7 @@ import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.math.Vector3;
+import com.badlogic.gdx.scenes.scene2d.Group;
 
 import sagittarius.model.*;
 
@@ -26,18 +27,26 @@ public class GameScreen extends BaseScreen {
 
         mainStage.setDebugAll(true); // TODO: disable later
 
+        // planets
+
+        Group planets = new Group();
+        
         Planet planet1 = new Planet(new Vector2(400, 400), 1000, 50, Color.BLUE);
-        mainStage.addActor(planet1);
-
+        planets.addActor(planet1);
+        
         Planet planet2 = new Planet(new Vector2(1400, 700), 1000, 100, Color.ORANGE);
-        mainStage.addActor(planet2);
+        planet2.addMoon(new Moon(planet2, 100, 10, 300, Color.MAGENTA));
+        planets.addActor(planet2);
 
-        Moon moon2_1 = new Moon(planet2, 100, 10, 300, Color.MAGENTA);
-        mainStage.addActor(moon2_1);
+        mainStage.addActor(planets);
+
+        // players
 
         Player player1 = new Player(planet1, Color.WHITE);
         mainStage.addActor(player1);
 
+        // others
+
         FPS fpsCounter = new FPS();
         uiStage.addActor(fpsCounter);