A faster starfield

Hi everyone, I made a starfield for a game I'm currently working on. It works well enough (I may try to improve the visuals later) but it gets slow when there are more than several hundred stars onscreen at once. I was wondering if anyone could look through the code and see if they had any ideas of how to improve the speed. Thanks a lot!

Type TStarfield
	Global list:TList = CreateList()
	
	Field sx#,sy#
	Field layersX:Float[][3]
	Field layersY:Float[][3]
	Field layersTime:Int[][3]
	Field nstars
	Field rate
	
	Method New()
		list.addlast(Self)
	End Method
	
	Function Create:TStarfield(sx#,sy#,density#)
		Local s:TStarfield = New TStarfield
		s.nstars = sx*sy*density
		s.rate = 700
		
		For Local i = 0 To 2
			s.layersX[i] = New Float[s.nstars]
			s.layersY[i] = New Float[s.nstars]
			s.layersTime[i] = New Int[s.nstars]
			For Local t = 0 To s.nstars-1
				s.layersX[i][t]= Rnd(sx)'TStar.Create(Rnd(sx),Rnd(sy),255,255,255,3)
				s.layersY[i][t]= Rnd(sy)
			Next
		Next
		Return s
	End Function 
	
	Function DrawAll(x#,y#)
		For Local i:TStarfield = EachIn(list)
			i.draw(x#,y#)
		Next
	End Function
	
	Function UpdateAll(x#,y#)
		For Local i:TStarfield = EachIn(list)
			i.update(x#,y#)
		Next
	End Function
	
	Method Draw(x#,y#)
		Local time = MilliSecs()
		For Local t = 0 To 2
			Local tx = x*(t+1)/2
			Local ty = y*(t+1)/2
			For Local i = 0 To nstars-1
				If layersX[t][i]+tx>0 And layersX[t][i]+tx<GraphicsWidth() And layersY[t][i]+ty>0 And layersY[t][i]+ty<GraphicsWidth()
					If time-layersTime[t][i]<rate Then SetColor 128,128,128
					DrawOval layersX[t][i]+tx-(t+1)/2,layersY[t][i]+ty-(t+1)/2,t+1,t+1
					SetColor 255,255,255
				EndIf
			Next
		Next
	End Method
	
	Method Update(x#,y#)
		Local time = MilliSecs()
		For Local t = 0 To 2
			Local tx = x*(3-t)/2
			Local ty = y*(3-t)/2
			For Local i = 0 To nstars-1
				If layersX[t][i]+tx>0 And layersX[t][i]+tx<GraphicsWidth() And layersY[t][i]+ty>0 And layersY[t][i]+ty<GraphicsWidth()
					If time - layersTime[t][i]>rate And Rand(600) = 1 Then layersTime[t][i] = MilliSecs()
				EndIf
			Next
		Next
	End Method
End Type