Help with "bounce ball off wall code"

Cool I'll check it out. Meanwhile I made this:

Strict

Graphics 800,600,0

Global c:TCircle = TCircle.Create(0,0,50)
c.color = TColor.Create(255,255,255)
Global l:TLine = TLine.Create(100,100,400,400)
l.CalcLength()

While Not KeyHit(key_escape)
	'Place cicle where mouse is
	c.x = MouseX()
	c.y = MouseY()
	'Change colour depending on collision status 
	If ccCircleLineIntersect(c,l) Then
		c.color.set(255,0,0)		
	Else
		c.color.set(0,255,0)		
	EndIf
	
	'Draw the scene
	Cls
	c.Draw()
	l.draw()
	Flip	
Wend

'----------------------------------------------------
Type TCircle
	Field x#
	Field y#
	Field r# 'radius
	Field Color:TColor
	
	Function Create:TCircle(x,y,r)
		c:TCircle = New TCircle
		c.x=x
		c.y=y
		c.r=r
		Return c
	End Function
	
	Method Draw()
		If Color<>Null Then Color.Apply
		DrawOval(x-r,y-r,r*2,r*2)
		If Color<>Null Then Color.Restore
	End Method
End Type

Type TLine
	Field sx#
	Field sy#
	Field ex#
	Field ey#
	Field length#
	Field Color:TColor
	
	Function Create:TLine(sx,sy,ex,ey)
		l:TLine = New TLine
		l.sx=sx
		l.sy=sy
		l.ex=ex
		l.ey=ey
		Return l
	End Function

	Method CalcLength#()
		length = Sqr((ex-sx)*(ex-sx)+(ey-sy)*(ey-sy))
	End Method
	
	Method Draw(DrawLastPixel=True)
		If Color<>Null Then Color.Apply
		DrawLine(sx,sy,ex,ey,DrawLastPixel)
		If Color<>Null Then Color.Restore
	End Method

End Type

Type TColor 'I'm using American spelling to keep it more like the Blitz commands.
	Field R=0
	Field G=0
	Field B=0
	Field Alpha#=1
	
	Function Create:TColor(r,g,b,alpha#=1)
		Local c:TColor = New TColor
		c.Set(r,g,b,alpha)
		Return c
	End Function
	
	Method Set(tR,tG,tB,talpha#=1)
		R = tR
		G = tG
		B = tB
		Alpha = tAlpha
	End Method

	Method Get(tR Var,tG Var,tB Var)
		tR = R
		tG = G
		tB = B
	End Method
	
	Method GetFull(tR Var,tG Var,tB Var, tAlpha# Var)
		tR = R
		tG = G
		tB = B
		tAlpha = Alpha
	End Method
	
	Method Apply()
		SetColor R,G,B
		SetAlpha Alpha
	End Method
	
	Method ApplyNoAlpha()
		SetColor R,G,B
	End Method

	Method Copy(c:TColor)
		R=c.R
		G=c.G
		B=c.B
		Alpha=c.Alpha
	End Method
	
	Method Restore()
		SetColor 255,255,255
		SetAlpha 1
	End Method
End Type

Function ccCircleLineIntersect%(c:TCircle,l:TLine)
	'Make sure you precalc the line length
	Local x0# = c.x
	Local y0# = c.y
	Local x1# = l.sx
	Local y1# = l.sy
	Local x2# = l.ex
	Local y2# = l.ey
	Local n# = Abs((x2-x1)*(y1-y0)-(x1-x0)*(y2-y1))	
	Local d# = l.length
	Local dist# = n/d
	If dist > c.r Return False
	Local d1# = Sqr((x0-x1)*(x0-x1)+(y0-y1)*(y0-y1))
	If d1-c.r > d Return False
	Local d2# = Sqr((x0-x2)*(x0-x2)+(y0-y2)*(y0-y2))
	If d2-c.r > d Return False
	Return True
End Function

The circle goes red when it's over the line. I do have a bit of a problem with the circle near the end points though. Perhaps the line needs to be "infinite" in length? But then I couldn't make a square :-(

Now I have to work out the angle of reflection...