bull & bear Strength for Amibroker (AFL)

_SECTION_BEGIN("bull & bear Strength");
SetChartBkColor(ParamColor("Outer panel",colorWHITE)); // color of outer border 

//---------------------------
Mdb=MA(C, 20);
bull=H - EMA(C,13);
bear=L - EMA(C,13);
upLine = C-MdB;
downLine = -(bull+bear);
centerLine=0;
Plot(upLine,"",colorGreen,1);
Plot(downLine,"",colorRed,1);
Plot(centerLine,"",colorBlack,1);
//----------------------------