hi im am making an hack and slash game from the BurgZergArcade tutorial and im facing an error that said : The type or namespace name `Skill' could not be found. Are you missing a using directive or an assembly reference? plz help me and explain to me whats wrong so i can improve my skill :)

code:

using UnityEngine;
using System.Collections;
using System;     //added to acces the enum class

public class BaseCharacter : MonoBehaviour {
    private string _name;
    private int _level;
    private uint _freeExp;

    private Attribute[] _primaryAttribute;
    private Vital[] _vital;
    private Skill[] _skill;

    public void Awake () {
       _name = string.Empty;
       _level = 0;
       _freeExp = 0;

       _primaryAttribut = new Attribute[Enum.GetValues(typeof(AttributeName)).Length];
       _vital = new Vital [Enum.GetValues(typeof(VitalName)).Length];
       _skill = new Skill [Enum.GetValues(typeof(VitalName)).Length];

       SetupPrimaryAttribute();
       SetupVitals();
       SetupSkills();
    }


    public string Name {
       get{ return _name;}
       set{name = value;}
    }

    public int Levvel {
       get{return _level;}
       set{_level = value;}
    }

    public uint FreeExp{
       get{return _freeExp;}
       set{_freeExp = value;}
    }

    public void AddExp (uint exp){
     _freeExp += exp;

       CalculateLevel();
    }

    //take the avg of all the players skill and assign that as the player level
    public void CalculateLevel(){

    }

    private void SetupPrimaryAttribute() {
       for(int cnt = 0; cnt < _primaryAttribute.Length; cnt++){
         _primaryAttribute[cnt] = new Attribute();
    }
    }

    private void SetupVitals(){
       for(int cnt = 0; cnt < _vital.Length; cnt++){
         _vital[cnt] = new Vital();
    }
    }

    private void SetupSkills(){
       for(int cnt = 0; cnt < _skill.Length; cnt++){
         _skill[cnt] = new Skill();
    }
    }

    public Attribute GetPrimaryAttribute(int index){
       return _primaryAttribute[index];

    }


    public Vital GetVital(int index){
       return _vital[index];
    }

    public Skill GetSkill(int index){
       return _skill[index];
    }

    private void SetupVitalMofifiers(){
       //healh
       GetVital((int)VitalName.Health).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Constitution), .5f));

       //energy mana
       GetVital((int)VitalName.Energy).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Constitution), 1));

       //mana
       GetVital((int)VitalName.Mana).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Willpower), 1));
       }

    private void SetupSkillModifiers(){
       //melee Offence
       GetSkill((int)SkillName,Melee_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Might),33f));
       GetSkill((int)SkillName,Melee_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Nimbleness),33f));
       //melee Defence
       GetSkill((int)SkillName,Melee_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),33f));
       GetSkill((int)SkillName,Melee_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Constitution),33f));
       //magic Offence
       GetSkill((int)SkillName,Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),33f));
       GetSkill((int)SkillName,Magic_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.WillPower),33f));
       //Magic Defence
       GetSkill((int)SkillName,Magic_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),33f));
       GetSkill((int)SkillName,Magic_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Willpower),33f));
       //Ranged Offence
       GetSkill((int)SkillName,Ranged_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Concentration),33f));
       GetSkill((int)SkillName,Ranged_Offence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),33f));
       //Ranged Defence
       GetSkill((int)SkillName,Ranged_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Speed),33f));
       GetSkill((int)SkillName,Ranged_Defence).AddModifier(new ModifyingAttribute(GetPrimaryAttribute((int)AttributeName.Nimbleness),33f));

    }

    public void StatUpdate(){
       for(int cnt = 0; cnt < _vital.Length; cnt++)
         _vital[cnt].Update();
       for(int cnt = 0; cnt < _skill.Length; cnt++)
         _skill[cnt].Update();
    }
}