diff --git a/src/main/java/dal/gravity/AbstractEarthPendulum.java b/src/main/java/dal/gravity/AbstractEarthPendulum.java
deleted file mode 100644
index 87b3460..0000000
--- a/src/main/java/dal/gravity/AbstractEarthPendulum.java
+++ /dev/null
@@ -1,23 +0,0 @@
-package dal.gravity;
-
-
-/**
- * Represents a pendulum on the planet Earth
- */
-public abstract class AbstractEarthPendulum extends AbstractPendulum {
-
-    /** gravitational constant */
-    public static final double GRAVITY = 9.80665;
-
-    /**
-     * Creates a new Pendulum instance using
-     * inLength: the string length (>0)
-     * inMass: the point mass (>0)
-     * inTheta0: angular displacement at t=0 (0<=theta0)
-     */
-    public AbstractEarthPendulum (double inLength, double inMass, double inTheta0) {
-	super (inLength, inMass, inTheta0, GRAVITY);
-    }
-
-}
-
diff --git a/src/main/java/dal/gravity/AbstractPendulum.java b/src/main/java/dal/gravity/AbstractPendulum.java
index 1b59a5a..2548930 100644
--- a/src/main/java/dal/gravity/AbstractPendulum.java
+++ b/src/main/java/dal/gravity/AbstractPendulum.java
@@ -5,8 +5,10 @@
  */
 public abstract class AbstractPendulum {
 
-
-    /* instance variables - string length, point mass, angular displacement
+//abstract class
+    /** gravitational constant */
+	public static final double GRAVITY = 9.80665;
+	/* instance variables - string length, point mass, angular displacement
      * at t=0, constant for local gravitational field in m/s^2 (e.g., 9.81 on Earth)
      */
     private double stringLength, pointMass;
diff --git a/src/main/java/dal/gravity/PendulumRunner.java b/src/main/java/dal/gravity/PendulumRunner.java
index 2c61033..2a4a6be 100644
--- a/src/main/java/dal/gravity/PendulumRunner.java
+++ b/src/main/java/dal/gravity/PendulumRunner.java
@@ -7,7 +7,7 @@
  * versus the Euler algorithm approximation
  */
 public class PendulumRunner {
-
+//run the main
     public static void main (String [] args) {
 	NumberFormat nf = NumberFormat.getInstance ();
 	nf.setMaximumFractionDigits (3);
diff --git a/src/main/java/dal/gravity/RegularPendulum.java b/src/main/java/dal/gravity/RegularPendulum.java
index 65b9014..2ab278e 100644
--- a/src/main/java/dal/gravity/RegularPendulum.java
+++ b/src/main/java/dal/gravity/RegularPendulum.java
@@ -3,7 +3,7 @@
 /**
  * Represents a pendulum
  */
-public class RegularPendulum extends AbstractEarthPendulum {
+public class RegularPendulum extends AbstractPendulum {
     private double delta, iterations = 0;
     private double dissipation;
     private double lastTheta, lastVel, lastAccel;
@@ -13,7 +13,7 @@ public class RegularPendulum extends AbstractEarthPendulum {
      */
     public RegularPendulum (double inLength, double inMass, double inTheta0, 
 		     double inDelta, double inDiss) {
-	super (inLength, inMass, inTheta0);
+	super (inLength, inMass, inTheta0, GRAVITY);
 	delta=inDelta;
 	dissipation = inDiss;
 	lastVel = 0;
@@ -25,7 +25,7 @@ public RegularPendulum (double inLength, double inMass, double inTheta0,
 		     double inDelta) {
 	this (inLength, inMass, inTheta0, inDelta, 0);
     }
-
+   
     public void step () {
 	iterations++;
 	lastTheta = lastTheta + lastVel*delta;
diff --git a/src/main/java/dal/gravity/SimplePendulum.java b/src/main/java/dal/gravity/SimplePendulum.java
index 5c7bf30..947c6b8 100644
--- a/src/main/java/dal/gravity/SimplePendulum.java
+++ b/src/main/java/dal/gravity/SimplePendulum.java
@@ -3,10 +3,10 @@
 /**
  * Represents pendulums exhibiting (approximately) simple harmonic motion
  */
-public class SimplePendulum extends AbstractEarthPendulum {
+public class SimplePendulum extends AbstractPendulum {
 
     private double angularFrequency, periodOfMotion;
-
+//simple
     /**
      * Creates a new Pendulum instance using
      * inLength: the string length (>0)
@@ -14,7 +14,7 @@ public class SimplePendulum extends AbstractEarthPendulum {
      * inTheta0: angular displacement at t=0 (0<=theta0<=pi/6)
      */
     public SimplePendulum (double inLength, double inMass, double inTheta0) {
-	super (inLength, inMass, inTheta0);
+	super (inLength, inMass, inTheta0,GRAVITY);
 	angularFrequency = Math.sqrt (this.getGravitationalField () / this.getStringLength ());
 	periodOfMotion = 2 * Math.PI 
 	    * Math.sqrt (this.getStringLength () / this.getGravitationalField ());