GameExample

internal class Program
{
    public void Main()
    {
        var rust = new Rust();
        var lumio = new Lumio();

        var roberto = new Roberto();

        rust.Attack(roberto);

    }
}

public interface ITakeDamage
{
    void TakeDamage(int amount);
} 

public interface ITakeHealing
{
    void TakeHealing(int amount);
}

public abstract class Character : ITakeDamage, ITakeHealing
{
    public int Damage { get; set; }
    public int Health { get; set; }
    public virtual void DoSpecial() { };
    public virtual void HealFriend(ITakeHealing friend) {  };
    public virtual void Attack(ITakeDamage foe) { foe.TakeDamage(Damage) };
    public void TakeDamage(int amount) => Health -= amount;
    public void TakeHealing(int amount) => Health += amount;
} 

public abstract class Player : Character { };
public abstract class Enemy : Character { };

public class Rust : Player
{
    public Rust()
    {
        Health = 50;
        Damage = 2;
    }

    public override void HealFriend(ITakeHealing friend)
    {
        friend.TakeHealing(10);
    }
}

public class Lumio : Player
{
    public Lumio()
    {
        Health = 28;
        Damage = 5;
    }

    public override void DoSpecial()
    {
        // show flash for powerup
        Damage += 10;
    }
}

public class Roberto : Enemy
{
    public Roberto()
    {
        Health = 20;
        Damage = 5;
    }
}