diff --git a/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentArray.java b/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentArray.java
deleted file mode 100644
index 710b80c..0000000
--- a/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentArray.java
+++ /dev/null
@@ -1,121 +0,0 @@
-package nz.ac.massey.javaecs;
-/**
- * Component Array
- * Defines the data structure that component data is stored under.
- * Has a list of defined objects, and two associative maps that link
- * the position of the data with the entity number.
- * 
- * Therefore, every entity in entityComponentDataMap is valid, so
- * no additional sorting is required
- * 
- * 
- * Contributors:
- * Brychan Dempsey - brychand@hotmail.com
- * 
- */
-
-import java.util.Map;
-import java.util.HashMap;
-import java.util.List;
-import java.util.ArrayList;
-
-/**
- * Stores component data in a packed interal list, and provides methods for accessing this data 
- */
-class ComponentArray{
-    // The object data array
-    private List<Object> componentArray;
-    // The mappings between data and entity
-    private Map<Entity, Integer> entityComponentDataMap;
-    private Map<Integer, Entity> componentDataEntityMap;
-
-    public ComponentArray(int initialSize){
-        componentArray = new ArrayList<>(initialSize);
-        entityComponentDataMap = new HashMap<>(initialSize);
-        componentDataEntityMap = new HashMap<>(initialSize);
-    }
-    /**
-     * Gets the data Object associated with the entity.
-     * @param entity the entity to find data for
-     * @return the Object if the data exists, else null
-     */
-    protected Object getData(Entity entity){
-        try{
-            return componentArray.get(entityComponentDataMap.get(entity));
-        }
-        catch (NullPointerException ex){
-            Engine.writeErr("Attempted to retrieve non-existent data for unassigned entity: " + entity.getValue());
-            return null;
-        }
-        catch (IndexOutOfBoundsException e){
-            Engine.writeErr("Index out-of-bounds for entity: " + entity.getValue());
-            return null;
-        }
-    }
-
-    /**
-     * Inserts the provided component and associates it with the entity.
-     * @param entity the entity to associate data to
-     * @param component the component data
-     * @return true if successful, false if the entity is already subscribed to the component
-     */
-    protected boolean insertData(Entity entity, Object component){
-        if (entityComponentDataMap.containsKey(entity)){
-            Engine.writeErr("Entity is already subscribed to the component");
-            return false;
-        }
-        // Put data at the end of the componentArray
-        int index = componentArray.size();
-        entityComponentDataMap.put(entity, index);
-        componentDataEntityMap.put(index, entity);
-        componentArray.add(component);
-        return true;
-    }
-
-    /**
-     * Moves component data to another entity. (Copies, deletes and inserts data)
-     * @param sourceEntity
-     * @param destinationEntity
-     * @return 0 if successful, -1 if the object is null, -2 if a NullPointerException occurred, and -3 if inserting data failed
-     */
-    protected int moveData(Entity sourceEntity, Entity destinationEntity){
-        try{
-            Object data = entityComponentDataMap.get(sourceEntity);
-            if (data == null) return -1;
-            else if (insertData(destinationEntity, data))
-            {
-                removeData(sourceEntity);
-                return 0;
-            }
-            else return -3; 
-        }
-        catch (NullPointerException e){
-            return -2;
-        }
-    }
-
-    /**
-     * Removes the data associated with the entity.
-     * @param entity the entity to remove the data from
-     * @return true if the data was removed. If the data isn't found then returns false
-     */
-    protected boolean removeData(Entity entity){
-        if (!entityComponentDataMap.containsKey(entity)){
-            Engine.writeErr("Attempted to remove non-existent entity: " + entity.getValue());
-            return false;
-        }
-        // Get the componentData index of the entity
-        int removedComponentDataIndex = entityComponentDataMap.get(entity);
-        // Replace the removed component with the last component in the array
-        componentArray.set(removedComponentDataIndex, componentArray.get(componentArray.size() -1));
-        // update the data positions in the map
-        Entity lastEntity = componentDataEntityMap.get(componentArray.size()-1);
-        entityComponentDataMap.replace(lastEntity, removedComponentDataIndex);
-        componentDataEntityMap.replace(removedComponentDataIndex, lastEntity);
-        // Finally, remomve the last elements
-        entityComponentDataMap.remove(entity);
-        componentDataEntityMap.remove(componentArray.size() -1);
-        componentArray.remove(componentArray.size() -1);
-        return true;
-    }
-}
\ No newline at end of file
diff --git a/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentManager.java b/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentManager.java
index fb56e88..169e4a7 100644
--- a/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentManager.java
+++ b/javaecs/src/main/java/nz/ac/massey/javaecs/ComponentManager.java
@@ -17,9 +17,11 @@ import java.util.HashMap;
  * Manages the addition, sorting and retrieving of components and component data
  */
 class ComponentManager{
-    private Map<Type, ComponentArray> componentArrays = new HashMap<>();
-    private Map<Type, Integer> componentPosIndex = new HashMap<>();
+    private Map<Type, Map<Entity, Object>> componentArrays = new HashMap<>();
+    // Need to be able to map bit indices and component types
     private Map<Integer, Type> indexComponentType = new HashMap<>();
+    private Map<Type, Integer> componentTypeIndex = new HashMap<>();
+    // 
 
     /**
      * Adds the specified component to the provided entity.
@@ -30,7 +32,8 @@ class ComponentManager{
      * @param entity the entity to associate data to
      */
     protected boolean addComponentToEntity(Type componentType, Object componentData, Entity entity){
-        return componentArrays.get(componentType).insertData(entity, componentData);
+        componentArrays.get(componentType).put(entity, componentData);
+        return true;
     }
 
     /**
@@ -41,9 +44,7 @@ class ComponentManager{
         // HashMap lookups take time, use the known bitstates to avoid
         int index = entityRegistrations.nextSetBit(0);
         while(index != -1){
-            if (!componentArrays.get(indexComponentType.get(index)).removeData(entity)){
-                Engine.writeErr(indexComponentType.get(index).getTypeName());
-            }
+            componentArrays.get(indexComponentType.get(index)).remove(entity);
             index = entityRegistrations.nextSetBit(index+1);
         }
     }
@@ -55,7 +56,7 @@ class ComponentManager{
      * @return the Object data found, or null if it was not found
      */
     public Object getComponent(Type componentType, Entity entity){
-        return componentArrays.get(componentType).getData(entity);
+        return componentArrays.get(componentType).get(entity);
     }
 
     /**
@@ -65,7 +66,7 @@ class ComponentManager{
      */
     public Integer getComponentIndex(Type type){
         try{
-            return componentPosIndex.get(type);
+            return componentTypeIndex.get(type);
         }
         catch (NullPointerException e){
             return -1;
@@ -94,10 +95,10 @@ class ComponentManager{
      * @return true if the component was moved successfully, else false
      */
     public boolean moveComponentData(Entity sourceEntity, Entity destinationEntity, Type component){
-        if (componentArrays.get(component).moveData(sourceEntity, destinationEntity) == 0){
-            return true;
-        }
-        else return false;
+        Object data = componentArrays.get(component).get(sourceEntity);
+        componentArrays.get(component).put(destinationEntity, data);
+        componentArrays.get(component).remove(sourceEntity);
+        return true;
     }
 
     /**
@@ -109,9 +110,8 @@ class ComponentManager{
     public void moveAllComponentData(Entity sourceEntity, Entity destinationEntity, BitSet sourceRegistrations){
         int result = sourceRegistrations.nextSetBit(0);
         while (result != -1){
-            Type key = indexComponentType.get(result);
-            componentArrays.get(key).moveData(sourceEntity, destinationEntity);
-            result = sourceRegistrations.nextSetBit(result+1);
+            moveComponentData(sourceEntity, destinationEntity, indexComponentType.get(result));
+            result = sourceRegistrations.nextSetBit(result +1);
         }
     }
 
@@ -135,9 +135,9 @@ class ComponentManager{
             Engine.writeErr("Component " + type.getTypeName() + " is already registered");
             return false;
         }
-        componentArrays.put(type, new ComponentArray(arraySize));
-        indexComponentType.put(componentPosIndex.size(), type);
-        componentPosIndex.put(type, componentPosIndex.size());
+        componentArrays.put(type, new HashMap<>());
+        indexComponentType.put(componentTypeIndex.size(), type);
+        componentTypeIndex.put(type, componentTypeIndex.size());
         return true;
     }
 
@@ -149,6 +149,7 @@ class ComponentManager{
      * @param entity the entity to remove the component from
      */
     public boolean removeComponentFromEntity(Type componentType, Entity entity){
-        return componentArrays.get(componentType).removeData(entity);
+        componentArrays.get(componentType).remove(entity);
+        return true;
     }
 }
\ No newline at end of file
diff --git a/javaecs/src/main/java/nz/ac/massey/javaecs/ECSSystem.java b/javaecs/src/main/java/nz/ac/massey/javaecs/ECSSystem.java
index 773ef00..29e0e7f 100644
--- a/javaecs/src/main/java/nz/ac/massey/javaecs/ECSSystem.java
+++ b/javaecs/src/main/java/nz/ac/massey/javaecs/ECSSystem.java
@@ -16,24 +16,45 @@ import java.util.Set;
 import java.util.BitSet;
 import java.util.HashSet;
 
+/**
+ * Abstract class that all systems should inherit from<p>
+ * Defines four required components:
+ * <ol>
+ * <li>The list of <b>entities</b> that have all the components required for this system</li>
+ * <li>The <b>BitSet</b> of component registrations required for this system</li>
+ * <li>The <b>init()</b> function, where logic that needs to be run once is performed</li>
+ * <li>The <b>update(dt)</b> function, where logic that needs to be run regularly is performed. <i>dt is the delta time in millseconds</i></li>
+ * </ol>
+ * Additionally, the object constructor should define the actual values of the BitSet.<p>
+ * Additional functions can be implemented as required.
+ */
 public abstract class ECSSystem{
     protected Set<Entity> entities = new HashSet<>();
     protected BitSet registrationSet;
 
+    public ECSSystem(){
+        registrationSet = new BitSet();
+    }
+
     public BitSet getRegistrationSet(){
         return registrationSet;
     }
 
     /**
      * Functionality that should be run only once.
-     * Implement additional parameterised init() functions as required.
+     * Implement additional parameterised <b>init()</b> functions as required.
+     * <p>
+     * This is distinct from the constructor as this may be run as required any time between
+     * the construction and <b>update(dt)</b>. It is not intended to set the actual bits of <b>registrationSet</b>
+     * in this function; that should be performed in the constructor.
+     * @throws Exception can return exceptions to the main program if an issue occurred. 
      */
-    public abstract void init();
+    public abstract void init() throws Exception;
     
     /**
      * Functionality that is expected to be called regularly
      * Intended as a template only; may be superficially implemented.
-     * Implement additional parameterised update() functions as required.
+     * Implement additional parameterised <b>update()</b> functions as required.
      * @param dt delta-time; the change in time in milliseconds since this function was last run
      */
     public abstract void update(double dt);
diff --git a/javaecs/src/main/java/nz/ac/massey/javaecs/Entity.java b/javaecs/src/main/java/nz/ac/massey/javaecs/Entity.java
index d77f48c..e2439a2 100644
--- a/javaecs/src/main/java/nz/ac/massey/javaecs/Entity.java
+++ b/javaecs/src/main/java/nz/ac/massey/javaecs/Entity.java
@@ -5,7 +5,7 @@ import java.lang.reflect.Type;
 /**
  * Entity class. 
  * Whilst an entity is just an Integer, and using Integer values
- * would be more performant (no function call, primitive arrays & etc.), it is encapsulated to help
+ * would be more performant (no function call, primitive arrays and etc.), it is encapsulated to help
  * distinguish between entities and Integers. Also, in this form it may be extended to also include things
  * like names, grouping, specific ordering etc
  */
@@ -56,12 +56,11 @@ public class Entity {
     /**
      * Adds the provided component to this entity.
      * <p>
-     * <b>This function calls addComponent() in the engine,</b> so
+     * <b>This function calls <i>Engine.addComponent(Entity, Type, Object)</i></b>, so
      * that should be used instead.
      * @deprecated This function is not ECS-like.
      * It is provided as an auxilliary method, that will be more
      * intuitive to those familiar with OO design
-     * @see Engine.addComponent() - which this function makes a call to
      * @param componentType the class type of the component to add
      * @param componentData the component data
      * @return true if successful
@@ -74,12 +73,11 @@ public class Entity {
     /**
      * Removes the provided component from this entity.
      * <p>
-     * <b>This function calls removeComponent() in the engine,</b> so
+     * <b>This function calls <i>Engine.removeComponent(Entity, Type)</i></b>, so
      * that should be used instead.
      * @deprecated This function is not ECS-like.
      * It is provided as an auxilliary method, that will be more
      * intuitive to those familiar with OO design
-     * @see Engine.removeComponent() - which this function makes a call to
      * @param componentType the class type of the component to remove
      * @return true if successful
      */
@@ -91,12 +89,11 @@ public class Entity {
     /**
      * Gets the component data associated to this entity.
      * <p>
-     * <b>This function calls getComponentData() in the engine,</b> so
+     * <b>This function calls <i>Engine.getComponentData()</i></b>, so
      * that should be used instead.
      * @deprecated This function is not ECS-like.
      * It is provided as an auxilliary method, that will be more
      * intuitive to those familiar with OO design
-     * @see Engine.getComponentData() - which this function makes a call to
      * @param componentType the class type of the component to fetch data from
      * @return the data Object, which requires casting
      */