USTRUCT(BlueprintType)  //again BlueprintType means you can use this structure in Blueprints.
struct FLevelData   //name of structure - need start with 'F' this structure will hold level data which will be displayed in level selection screen.
{
    GENERATED_USTRUCT_BODY()  // without this you will get compile errors

        UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")  // this means you can break structure in blueprints + it will be replicated. //Always use UPROPERTY() macro in variables.
        ELevelEnemyType EnemiesType;  // declaring ELevelEnemy Enum in ELevelData structure.

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        ELevelDifficulty LevelDifficulty;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        float LevelTime;   // levels will be time based that's why we need to declare how long we can play before end of the level.

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        float HiScore;     // we will store HiScore in this structure so it can be seen in level selection screen.

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        UObject* SequenceData; // reference to Object which will store sequence of enemies for the level.

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        UMaterial* LevelIcon;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        UMaterial* LevelBackground;

    UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Level Data")
        FString LevelToLoad; //name of the level to load.

    //Constructor
    FLevelData()
    {
        //Always initialize your USTRUCT variables!
        //   exception is if you know the variable type has its own default constructor
        EnemiesType = ELevelEnemyType::ET_Robots;
        LevelDifficulty = ELevelDifficulty::LD_Easy;
        LevelTime = 120.0f;
        HiScore = 0.0f;
        SequenceData = NULL; //means clear reference
    }
};