Setalpha by distance traveled

Here ist also some old code in wich i tried to generate a Starfield:

SuperStrict

Rem
Framework BRL.GLMax2D
Import BRL.LinkedList
Import BRL.Random
EndRem

Incbin "star.png"

Type TStarfield

	Global Starlist:TList = New TList
	
	Global center_X:Double
	Global center_Y:Double
	
	Global x_home:Int
	Global y_home:Int
	Global height:Int
	Global width:Int
	
	Global accel:Double = 1.05
	Global fade:Double = 1.05
	Global max_age:Int = 500
	
	Global image:TImage 
	
	Field x:Double
	Field y:Double
	Field vx:Double
	Field vy:Double
	
	Field red:Int
	Field green:Int
	Field blue:Int
	
	Field age:Int
	
	Field inuse:Byte
	
	Method New()
		Self.Emit()
	 	ListAddLast(Starlist, Self)
	EndMethod
	
	Method Draw() 
		If inuse > 0 Then
			Local oldBlend:Int = GetBlend()
			Local oldAlpha:Double = GetAlpha() 
			Local oldMaskRED:Int
			Local oldMaskGREEN:Int
			Local oldMaskBLUE:Int
			
			GetMaskColor(oldMaskRED , oldMaskGREEN , oldMaskBLUE) 
			
			SetMaskColor(0,0,0)			
			SetBlend(ALPHABLEND)
			
			If age < max_age
				SetAlpha(1.0-Float(age)/Float(max_age))
			Else
				SetAlpha(1.0)
			EndIf
			
			DrawImage(image , x , y) 
			
			SetBlend oldBlend
			SetAlpha oldAlpha
			SetMaskColor(oldMaskRED , oldMaskGREEN , oldMaskBLUE)
			
		EndIf
	EndMethod
	
	Method Update() 
		If inuse > 0
			x :+ vx
			y :+ vy
			
			vx :* accel
			vy :* accel
			
			age :- 1
			If age = 0 Then inuse = 0

			If x < x_home Or x > (x_home + width) Then inuse = 0
			If y < y_home Then inuse = 0
			If y > (y_home + height) Then inuse = 0
		Else
			Self.Emit()
		EndIf
	EndMethod
	
	Method Emit() 
		
		vx = - .5 + RndDouble() 
		vy = - .5 + RndDouble() 
				
		x = Center_X
		y = Center_Y
		
		age = max_age
		
		inuse = 1
	EndMethod
	
	Function UpdateAll() 
		For Local s:TStarfield=EachIn Starlist
			s.Update() 
		Next
	EndFunction
	
	Function DrawAll() 
		For Local s:TStarfield=EachIn Starlist
			s.Draw() 
		Next
	EndFunction
	
	Function SetAcceleration(acceleration:Double) 
		accel = acceleration
	EndFunction
	
	Function EmitStars(amount:Int) 
		For Local i:Int = 1 To amount
			Local temp:TStarfield = New TStarfield
		Next
	EndFunction
	
	Function SetCenter(in_x:Int , in_y:Int) 
		center_X = in_x
		center_Y = in_y
	EndFunction
	
	Function SetFade(fade:Double) 
		
	EndFunction
	
	Function SetImage(picture:TImage) 
		image = picture
	EndFunction
	
	Function SetDimensions(x:Int , y:Int , w:Int , h:Int) 
		x_home = x
		y_home = y
		width = w
		height = h
		SetCenter(x + w/2, y + h/2)
	EndFunction

EndType


Graphics 800 , 600, 0, 60, GRAPHICS_BACKBUFFER|GRAPHICS_ALPHABUFFER
'Graphics 800 , 600

SetColor 0 , 0 , 0
Cls

Local picture:Timage = LoadImage("incbin::star.png" , -1)

If  picture = Null
	RuntimeError "Could not load Picture!"
EndIf

TStarfield.SetDimensions(0,0,800,600)
TStarfield.SetAcceleration(1.01) 
TStarfield.SetFade(1.5) 
TStarfield.SetImage(picture) 

Local StarCount:Int = 1500

Repeat

	If StarCount > 0
		TStarfield.EmitStars(1) 
		Starcount :- 1
	Endif

	SetColor 255 , 255 , 255

	Cls
	
	TStarfield.UpdateAll() 
	TStarfield.DrawAll() 
	
	Flip
		
Until AppTerminate() Or KeyDown(KEY_ESCAPE) 

This ist the Image