With the newly implemented "select_mode", it is now necessary to change
select_mode as soon as "on_button_press_event" realizes a tile has
been clicked on.
if (event->x >= tile_x && event->x <= (tile_x + TILE_WIDTH) &&
event->y >= tile_y && event->y <= (tile_y + TILE_HEIGHT) )
{
if (event->x >= tile_x && event->x <= (tile_x + TILE_WIDTH) &&
event->y >= tile_y && event->y <= (tile_y + TILE_HEIGHT) )
{
game->current_tile = i;
game->diff_x = event->x - tile_x;
game->diff_y = event->y - tile_y;
game->current_tile = i;
game->diff_x = event->x - tile_x;
game->diff_y = event->y - tile_y;