THIS_MOUSE_X = round(mouse_x / 24) * 24;
       THIS_MOUSE_Y = round(mouse_y / 24) * 24;
       
       if (mouse_check_button_pressed(mb_left))  
       {                         
             if (!position_meeting(THIS_MOUSE_X, THIS_MOUSE_Y, all))
             {
                 instance_create(THIS_MOUSE_X, THIS_MOUSE_Y, o_Block);
             }
       }