df=30;
normalArea = NormalDistribution(1) - 0.5;

NewWindow(
	"t-distribution",
	VListBox(
	   gr=Graph(Framesize(300,300),Xscale(-3.5,3.5),Yscale(0,0.5), 
		Double Buffer,
		scl = normalArea/(tDistribution(1,df)-0.5);
		YFunction(scl * tDensity(x*scl,df),x);
		Text({0.5, 0.02},"df = ",char(df,3,1));
		// Handle(0,df/40,df=floor(40*y)+1);
		Pen color("red");
		YFunction(Normal Density(x),x);
		),
	   HListBox(SliderBox(1,32,df,gr<<reshow),
				TextBox("Degrees of Freedom Slider")))
);