When running my code, I keep getting the following errors:

AppData\Local\Temp\ccemqO2g.o:main.cpp:(.rdata$.refptr.game[.refptr.game]+0x0): undefined reference to `game' `  
`AppDataLocalTempccemqO2g.o:main.cpp:(.rdata$.refptr.hero[.refptr.hero]+0x0): undefined reference to `hero'

compiler is g++

hero is a base class for 3 others that only really use a slightly modified constructor that changes only the values of the class and is also inheriting fron entity, which has less arguments

here’s the header file:

#include "Entity.h"
#pragma once
class Hero : public Entity {
public:
    int xp;
    int lvl;
    int cd;
    bool clericcheck;

    Hero(int HP, int Damage);
    void heal(int &potion_count);
    void level_up();
};

.cpp file:

#include "Hero.h"
#include <iostream>
#pragma once

Hero::Hero(int HP, int Damage) : Entity(1000, 100), xp(0), lvl(0), cd(0), clericcheck(false) {}

void Hero::heal(int &potion_count) {
    if (!clericcheck) {
        if (potion_count > 0) {
            HP += 400 + (20 * lvl);
            potion_count -= 1;
            std::cout << "Ez jól esett! - " << 400 + (20 * lvl) << " életponttal tovább bírod a fájdalmat. Még " << potion_count << " adag maradt." << std::endl;
        } else {
            std::cout << "Ez üres! - Kifogytál az életerő italból." << std::endl;
        }
    } else {
        if (cd == 0) {
            HP += 400 + (20 * lvl);
            std::cout << "SZENTELT FÉNY! - " << 400 + (20 * lvl) << " életponttal tovább bírod a fájdalmat." << std::endl;
            cd += 2;
        } else {
            std::cout << "Még túl fáradt vagyok hozzá. - Töltési időből hátravan még: " << cd << " kör." << std::endl;
        }
    }
}

void Hero::level_up() {
    xp -= 1000 + (100 * lvl);
    lvl += 1;
    HP += int(1000 + 100 * lvl);
    Damage += int((5 / Damage) * lvl);
    std::cout << "Szintet léptél. n" << std::endl;
}

here’s the game’s header file (inventory is not implemented properly yet):

#include "Hero.cpp"
#include "Enemy.cpp"
//#include "Inventory.h"
#pragma once
class Game {
private:
    int turn_counter;
    bool easycheck;
    bool mediumcheck;
    bool hardcheck;
    bool firstcheck;
    bool Dshield_check;
    bool boss1check;
    bool boss2check;
    bool boss3check;
    int hulyementes;
    std::string kiiras;
    char choice;
public:
    bool crown_check;

    //Inventory inventory;
    Hero hero;
    Enemy enemy;

    Game();
    void menu();
    void diff();
    void gameplay(int difficulty);
    void endgame(int difficulty);
};

game.cpp:

#include "Game.h"
#include <cstdlib>
#include <ctime>
#include <iostream>
#include "Enemy.cpp"
#include "Hero.cpp"
#include "Inventory.cpp"
#include "Entity.cpp"
#include "Warrior.cpp"
#include "Ranger.cpp"
#include "Cleric.cpp"

using namespace std;

Game::Game() : turn_counter(0), enemy(1000, 100), easycheck(false), mediumcheck(false), hardcheck(false),
               firstcheck(true), Dshield_check(false), crown_check(false), boss1check(false), boss2check(false), boss3check(false),
               hulyementes(0), hero(1000,100), kiiras("Melyik szörnyet kéne megtámadni? (M --> menekulés, 1 --> könnyű, 2 --> közepes, 3 --> nehéz) ") {}

void Game::menu() {
    cout << "Üdvözöllek ebben az RPG-ben! Kérlek válaszd ki hősödet!" << endl;
    int valasztas = 0;
    while (valasztas == 0) {
        while (this->hulyementes == 0) {
            cout << "1 --> warrior, az örjöngő öldöklő; 2 --> cleric, az ordító gyógyító; 3 --> ranger, a fejlövő cselszövő): ";
            std::cin >> this->choice;
            if (this->choice == '1' || this->choice == '2' || this->choice == '3') {
                this->hulyementes++;
            } else {
                cout << "Normálisat válassz!" << endl;
            }
        }
        
        if (this->choice == 1) {
            this->hero = Warrior(1000, 100);
            valasztas++;
        } else if (this->choice == 2) {
            this->hero = Cleric(1000, 100);
            valasztas++;
        } else if (this->choice == 3) {
            this->hero = Ranger(1000,100);
            valasztas++;
        } else {
            cout << "Ha azt mondom, hogy 1, 2, vagy 3, akkor nincs itt más választásod!" << endl;
        }
        this->diff();
    }
}

void Game::diff() {
    char difficulty;
    this->hulyementes = 0;
    while (this->hulyementes == 0) {
        cout << this->kiiras;
        std::cin >> difficulty;
        if (difficulty == '1' || difficulty == '2'|| difficulty == '3') {
            this->hulyementes++;
        } else if (difficulty == '4' || difficulty == '5' || difficulty == '6') {
            if (!this->firstcheck) {
                this->hulyementes++;
            } else {
                cout << "Ez a szint még nem elérhető." << endl;
            }
        } else if (difficulty == 'm' || difficulty == 'M') {
            this->hulyementes++;
            cout << "Bátor Sir Robin bátran elfutott." << endl;
            exit(0);
        } else {
            cout << "Normálisat válassz!" << endl;
        }
    };
    this->gameplay(difficulty);
}

void Game::gameplay(int difficulty) {
    //if (inventory.sisak == "Összetört királyné koronája") {
    //    this->crown_check = true;
    //}
    switch (difficulty) {
        case 1:
            this->enemy = EnemyEasy(1000, 100);
            break;
        case 2:
            this->enemy = EnemyNormal(1000, 100);
            break;
        case 3:
            this->enemy = EnemyHard(1000, 100);
            break;
        case 4:
            this->enemy = Boss(1000, 100, "A vérszomjas");
            break;
        case 5:
            this->enemy = Boss(1000, 100, "Doran pajzsa");
            break;
        case 6:
            this->enemy = Boss(1000, 100, "Tuskevért");
            break;
        default:
            cout << "Ez a szint még nem elérhető." << endl;
            return;
    }
    this->hulyementes = 0;
    while (this->hero.HP > 0 && this->enemy.HP > 0) {
        while (this->hulyementes == 0) {
            cout << "A hős életereje: " << int(this->hero.HP) << " , A boss életereje: " << int(this->enemy.HP) << endl;
            cout << "1 = támadás, 2 = heal: ";
            char move;
            std::cin >> move;
            if (move == '1') {
                this->enemy -= this->hero;
                this->hero -= this->enemy;
                this->turn_counter++;
            } else if (move == '2') {
                //this->hero.heal(inventory.potion_count);
                this->turn_counter++;
            } else {
                cout << "Ez nem egy lehetséges tett." << endl;
            }
            if (this->hero.HP <= 0 || this->enemy.HP <= 0) {
                this->hulyementes++;
            }
        }
        this->hulyementes = 0;
    }
    this->endgame(difficulty);
}

void Game::endgame(int difficulty) {
    srand(time(0));
    if (this->hero.HP > 0) {
        int poti_rng = 1;
        int loot_rng = rand() % 4 + 1;
        cout << "n n n n Gratulálok, legyőzted a szörnyet! jutalmad: n" << endl;
        this->hero.xp += 150 + (250 * difficulty);
        this->kiiras += std::to_string(150 + (250 * difficulty)) + " xp n";
        if (this->Dshield_check) {
            this->hero.HP += this->hero.HP * 0.1;
        }
        if (poti_rng == 1) {
            if (this->hero.clericcheck) {
                this->hero.xp += 100;
                this->kiiras += "Az életerő ital felesleges számodra, a fény által kaptál 100 xp-t. n";
            } else {
                //inventory.potion_count++;
                this->kiiras += "1 Potion n";
            }
        }
        /*if (loot_rng == 1) {
            int rarity_rng = rand() % 101;
            if (15 > rarity_rng >= 0) {
                loot.get(rand() % 4, 2);
                this->kiiras += "1 epic item n";
            } else if (40 > rarity_rng >= 15) {
                loot.get(rand() % 4, 1);
                this->kiiras += "1 rare item n";
            } else if (100 > rarity_rng > 40) {
                loot.get(rand() % 4, 0);
                this->kiiras += "1 common item n";
            }*/
        //}
        cout << this->kiiras << endl;
        if (difficulty == 1) {
            this->easycheck = true;
        } else if (difficulty == 2) {
            this->mediumcheck = true;
        } else if (difficulty == 3) {
            this->hardcheck = true;
        } else if (difficulty == 4) {
            cout << "Gratulálok! Legyőzted Kardos Karcsit!" << endl;
            //if (!this->boss1check) {
                //loot.get(0, 3);
            //} else 
            {
                this->hero.xp += 1000 + (100 * this->hero.lvl);
            }
        } else if (difficulty == 5) {
            cout << "Gratulálok! Legyőzted Pajzsos Palit!" << endl;
            //if (!this->boss2check) {
                //loot.get(1, 3);
            //} else 
            {
                this->hero.xp += 1000 + (100 * this->hero.lvl);
            }
        } else if (difficulty == 6) {
            cout << "Gratulálok! Legyőzted Páncélos Pált!" << endl;
            //if (!this->boss3check) {
            //    loot.get(2, 3);
            //} else 
            {
                this->hero.xp += 1000 + (100 * this->hero.lvl);
            }
        }
        if (this->hero.xp >= 1000 + (100 * this->hero.lvl)) {
            this->hero.level_up();
        }
        if (this->easycheck && this->mediumcheck && this->hardcheck && this->firstcheck) {
            //loot.get(3, 3);
            this->firstcheck = false;
            this->kiiras += "nbossok: Kardos Karcsi (4), Pajzsos Pali (5), Páncálos Pál (6)";
        }
        //inventory.inventory_management();
        this->diff();
    } else if (this->crown_check) {
        cout << "FELTÁMADTAM!" << endl;
        this->hero.HP += int(1000 + (100 * this->hero.lvl));
        if (this->hero.lvl > 1) {
            this->diff();
            this->hero.lvl--;
        } else {
            cout << "A végzet még a legnagyobb hősöket is utoléri. n Kalandod Itt véget ért." << endl;
            exit(0);
        }
    } else {
        cout << "A végzet még a legnagyobb hősöket is utoléri. n Kalandod Itt véget ért." << endl;
        exit(0);
    }
}

main.cpp:

#include "Game.cpp"

int main() {
    Game game;
    game.menu();
    return 0;
}

I’ve tried mixing around the headers, looked at every instance of ‘hero’ being used and I can’t find anything.