How to change the upper left coordinate reference and center coordinate reference of the drawn figure

#include "DxLib.h"
# include <stdlib.h>

const char TITLE[] = "K0: Title";

constint WIN_WIDTH = 600; // Window Width
constint WIN_HEIGHT=400;// Window width

int WINAPI WinMain(_In_HINSTANCE hInstance,_In_opt_HINSTANCE hPrevInstance,_In_LPSTR lpCmdLine,_In_intnCmdShow)
{
    ChangeWindowMode (TRUE); // Set to window mode
    // To prevent manually changing the window size and scaling to fit the window size
    SetWindowSizeChangeEnableFlag(FALSE,FALSE);
    SetMainWindowText (TITLE); // Change Title
    SetGraphMode(WIN_WIDTH,WIN_HEIGHT,32); // Set the maximum screen size, number of color bits (to match monitor resolution)
    SetWindowSizeExtendRate (1.0); // Set screen size (set in ratio to resolution)
    SetBackgroundColor (0x00, 0x00, 0xFF); // Set the background color of the screen

    // Initialize Dx Library
    if(DxLib_Init()==-1) {return-1;}

    // (Double Buffer) Drawing destination graphic area designates the back side
    SetDrawScreen(DX_SCREEN_BACK);

    // Variable declaration and loading of resource data such as images

    // Declare variables to use in game loops
    char keys [256] = {0}; // For latest keyboard information
    char oldkeys [256] = {0}; // Keyboard information before loop (frame)

    intposX;// center coordinates of the rectangle to be described
    int posY;//
    intradius;// square radius

    radius = 60;
    posX=300;
    posY = 200;

    int ClickX, ClickY, Button, LogType; // Square Move
    int DrawFlag, DrawX, DrawY, DrawColor;
    int spaceFlag = 0;
    inttx=posX;
    intty=posY;
    int MouseX;
    int MouseY;

    DrawFlag=FALSE;
    DrawX = 0;
    DrawY=0; DrawColor=0;
    // game loop
    while(1)
    {
        // Save the latest keyboard information as one frame ago

        // Get the latest keyboard information
        GetHitKeyStateAll(keys);

        // Clear Screen
        ClearDrawScreen();
        //---------  Describe the program here -------------------------

        // Update Processing
        // Zoom in and out of squares
        if(keys[KEY_INPUT_UP] == 1) 
        {
            radius=radius+3;
        }
        if(keys[KEY_INPUT_DOWN] == 1) 
        {
            radius=radius-3;
        }
        // Move quadrilateral with mouse
        if (GetMouseInputLog2(&Button,&ClickX,&ClickY,&LogType,TRUE) == 0)
        {
            if(Button&MOUSE_INPUT_LEFT)!=0)
            {
                DrawFlag = TRUE;
                posX=ClickX;
                posY = ClickY;
            }
        }
        if(DrawFlag==TRUE)
        {
            DrawBox(posX-radius, posY-radius, posX+radius, posY+radius, DrawColor, TRUE);
        }
        // Replace coordinate criteria??
        if(keys[KEY_INPUT_SPACE] == 1)
        {
            spaceFlag = 1;
        }
        inttx=posX;
        intty=posY;
        if(spaceFlag==1){
            tx+=radius;
            ty+=radius;
            spaceFlag = 0;
        }
        spaceFlag = 0;

        DrawBox(tx-radius, ty-radius, tx+radius, ty+radius, GetColor (255, 255, 255), TRUE);

        // Get mouse coordinate position
        GetMousePoint (&MouseX, & MouseY);

        // Drawing processing

        DrawFormatString(0,15,GetColor(200,50,130), "Square x coordinates, Square y coordinates(%d, %d), posX, posY);
        DrawFormatString(0,30, GetColor(200,50,130), "Mouse coordinates x, Mouse coordinates y(%d,%d), MouseX, MouseY);
        //---------  So far, I've written a program -------------//
        ScreenFlip(); // (double buffer) back
        // 20 ms wait (pseudo 60 FPS)
        WaitTimer (20);
        // process information coming from a Windows system
        if(ProcessMessage()==-1)
        {
            break;
        }
        // ESC key presses out of loop
        if(CheckHitKey(KEY_INPUT_ESCAPE)==1)
        {
            break;
        }
    }
    // Dx library shutdown process
    DxLib_End();

    return 0;
}