# States and Inheritance
### Introduction
State behavior can be a little confusing when combined with inheritance. This article discusses how states and inheritance work together and things you should be aware of in your project when using States with Screens/Entities that inherit from other Screens/Entities.
### States Categories Create Classes
Every category in your project creates a class in generated code. For example, consider a Bullet entity with a category BulletAppearance.
BulletAppearance category
The generated includes a class called BulletAppearance with properties matching the variables assigned in the FRB Editor.
```csharp
public class BulletAppearance
{
public string Name;
public float BulletLifeDuration;
public string AnimationName;
public float SideBulletRadius;
public float SideBulletRotationSpeed;
public int MaxBullets;
...
```
### Derived Categories
If a category is added to a derived screen or entity, FlatRedBall checks if the same-named category exists in the base screen or entity. If the derived category matches the name of a category in the base, then this category is created as a derived class from the base category. Derived categories can be used to add additional states to the base.
For example, consider a base entity Bullet and a derived entity named BulletDerived each with a category named BulletAppearance.
BulletAppearance category in BulletDerived
BulletDerived defines a class named BulletAppearance which inherits from the base BulletAppearance class.
```csharp
public class BulletAppearance : Entities.Bullet.BulletAppearance
{
public string Name;
...
```
The derived entity includes a property that is of the derived type, so derived instances can assign this property in code.
```csharp
private BulletAppearance mCurrentBulletAppearanceState = null;
public new Entities.BulletDerived.BulletAppearance CurrentBulletAppearanceState
{
get
{
return mCurrentBulletAppearanceState;
}
set
{
mCurrentBulletAppearanceState = value;
...
```
The derived entity can add additional states to the category, but it cannot overwrite existing states. If a new state is added with the same name as a state in the base class, FlatRedBall marks it as an error by coloring the name text.
Derived category with a state that has the same name as a state in the base category is marked as an error
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