Explication une partie du code pour Snake C++

Bonjour,
Je suis en train de développer un jeux Snake en C++ mais je fais face à un certains nombres de problématiques auxquels je n'arrive pas à trouver solution.
J'ai trouvé un code mais je ne souhaite pas le copié, et faire quelques choses par moi même mais je sais que si j'arrive à comprendre ce code il me sera d'autant plus simple de faire le mien.
Si quelqu'un peut m'aider j'en serai extrêmement reconnaissant .
Un grnad merci à toute la communauté!!! :)

#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <conio.h>
#include <time.h>
 
void draw(char main[][75], int score);
void reset(char main[][75]);
void move(char main[][75], int &parts, int pastCounter, int past[][2], int &apples, int &score, int &quit);
void check (int &direction);
void directionn(int direction, int &pastCounter, int past[][2]);
void apple (int &apples, char main[][75]);
void quitGame (int score);
 
int main()
{   //past is an array to help direct when the snakes body will go, 
    //did it like this so the behind pieces will follow the snakes head
    int past[1000][2]; //second bracket: 0 is up, 1 is side
    int parts = 3; //number of snake pieces
    char main[23][75];   // 23 down, 73 wide is appropriate screen size
    int pastCounter = 6;  //used in the use of past 
    int direction = 0;
    int apples = 0;
    int score = 0;
    int quit = 0;
    int playAgain = 1;
    srand(time(0));
 
    //SetConsoleTextAttribute(GetStdHandle(STD_OUTPUT_HANDLE),2);  -- color if wanted
 
    for (int x = 0; x < 1000; x ++) 
    {
        for (int y = 0; y < 2; y ++)
        {
            past [x][y] = 0;
        }
    }
    past[pastCounter][0] = 1; //keep the game from crashing because if you hit the wall it kicks you from the wall
    past[pastCounter][1] = 1;
    while(quit == 0)
    {  //main rotation through all the game's functions.
        draw(main, score);
        check(direction);
        directionn(direction, pastCounter, past);
        reset(main);
        move(main, parts, pastCounter, past, apples, score, quit);
        Sleep(25); //pause to keep the game a normal speed...
        if (apples == 0)
        {  //place more apples only if they are all gone
            apple(apples, main); 
        }
         
    }
    quitGame(score);
    Sleep (10000);
    //getch();
 
}
void draw(char main[][75], int score)
{//draws the screen
    system("cls");
    printf ("Score : %d\n", score);
    for (int x = 0; x < 23; x ++)
    {
        for (int y = 0; y < 75; y ++)
        {
            printf ("%c", main[x][y]);
        }
        printf ("\n");
    }
 
} 
 
void reset(char main[][75])
{//resets the array to keep it from being filled with parts of snake that shouldn't be there after the snake has moved on
    for (int x = 0; x < 23; x++)
        {
            for (int y = 0; y < 75; y++)
            {
                if (main[x][y] == '@')
                {  //doesn't reset the apples
                    main[x][y] == '@';
                }
                else
                {
                    if (x == 0 || x == 22 || y == 0 || y == 74)
                    {//doesnt reset the border
                        main[x][y] = 177;
                    }
                    else
                    {
                        main[x][y] = ' ';
                    }
                }
            }
        }
}
 
void move(char main[][75], int &parts, int pastCounter, int past[][2], int &apples, int &score, int &quit)
{//moves the snake head, and has the body follow it
    if (past[pastCounter][0] == 22 || past[pastCounter][0] == 0)
    {  //if te snake is on the border of the game you loose
        quit = 1;
    }
    if (past[pastCounter][1] == 74 || past[pastCounter][1] == 0)
    {
        quit = 1;
    }
 
    for (int x = 0; x < parts; x++)
    {
        if (main[past[pastCounter - x][0]][past[pastCounter - x][1]] == '@')
        {  //if the snake (technically any part of the snake) eats and apple...
            apples--;
            parts++;
            score += 10;
        }
        if (main[past[pastCounter - x][0]][past[pastCounter - x][1]] == 'o')
        {  //if the snake eats itself
            quit = 1;
        }
        else
        {  //else the snakes new location is determined
        main[past[pastCounter - x][0]][past[pastCounter - x][1]] = 'o';
        }
    }
}
void check (int &direction)
{//checks if there has been user input
    int key = 0;
    if (kbhit())
    {
        key = -getch();
        switch (key)
        {
        case -72:
            direction = 2;
            break;  //up
        case -77:
            direction = 0;
            break; //right
        case -80:
            direction = 3;
            break; //down
        case -75:
            direction = 1;
            break; //left
        }
    }
         
}
void directionn(int direction, int &pastCounter, int past[][2])
{//based on user input, detects which directing the snake head should be going
    int right;//adding to the array itself did not work, so i worked around it.
    int down;
    right = past[pastCounter][1];
    down = past[pastCounter][0];
    switch (direction)
    {  //directs the snake based on direction
    case 0:
        right ++;
        break;
    case 1:
        right --;
        break;
    case 2:
        down --;
        break;
    case 3:
        down ++;
    }
 
    pastCounter ++;
    past[pastCounter][0] = down;
    past[pastCounter][1] = right;
}
void apple (int &apples, char main[][75])
{//places apples on the screen
    int up = 0;
    int left = 0;
    apples = 3;
 
    for (int x = 0; x < apples; x ++)
    { //places appples, only if theres no border of part of the snake already in the space
        up = (rand() % 22);
        left = (rand() % 74);
 
        if (main[up][left] == 'o')
        {
            apple(apples, main);
        }
        if (main[up][left] == '*')
        {
            apple(apples, main);
        }
        else
        {
            main[up][left] = '@';
        }
    }
}
 
 
 
 
void quitGame (int score)
{//quits and displays score
    int quit = 0;
    system ("cls");
    printf ("GAME OVER!!!!\n\n");
    printf ("You got a score of %d\n", score);

EDIT: Ajout de la coloration syntaxique.