nGraphic functions
nSetForeColor(short R, short G, short B);
nPaintRect(short x1, short y1, short x2, short y2);
nPaintCircle(short x1, short y1, short radius);
nPaintOval(short x1, short y1, short x2, short y2);
nInvertOval(short x1, short y1, short x2, short y2);