width -= dx;
else if (dx) /* general horizontal movement */
MarkTileDirty(x + SIGN(dx), y);
if (y < BY1) /* object enters playfield from the top */
{
width -= dx;
else if (dx) /* general horizontal movement */
MarkTileDirty(x + SIGN(dx), y);
if (y < BY1) /* object enters playfield from the top */
{