Timing changes query

this is a scope problem. all the varibles within the function are local and refreshed everythime the function is called (or set back to 0) which means your basicaly doing 0 + 0 & 0 - 0.

make x & y global and it should fix it.

[edit] in fact it does fix it :)

[edit 2]

Graphics 800,600,32
'load an image to tile
Global image=LoadImage("flake.png")
Global x, y
Global duration = 500 'millisecs = 1/2 sec
Global timer
Global dx = 1, dy = 1



While Not KeyHit(KEY_ESCAPE)

	function1()
	
	Flip;Cls

Wend

Function Function1()
TileImage image,x,y
'duration=500 'millisecs = 1/2 sec
'timer=MilliSecs()

'dx=1
'dy=1
	'move the tiled background
	x=x+dx
	y=y+dy
	
	If MilliSecs()>timer+duration
	dx=-dx
	dy=-dy
	timer=MilliSecs()
	End If

End Function

you need to globalize and init the other varibles too, by bet :D

[extra note]why your first code works: the varibles are in the program scope. why your second code dont work: the varibles are in the function scope and as a result go out of scope when the function is exited and the varibles are re init when you cal the function again.