[HolyDel]

примерно так

Graphics3D 800,600,32,1
SetBuffer BackBuffer()
SeedRnd MilliSecs()
For i=1 To 100
	Color Rnd(256),Rnd(256),Rnd(256)
	Rect Rnd(0,600),Rnd(0,400),Rnd(0,400),Rnd(0,400)
Next
CopyRect(0,0,800,600,0,0,BackBuffer(),FrontBuffer())
While Not KeyDown(1)
	Flip
Wend
fadescreen(4000)


Function fadescreen(time)
	dt#=time/255
	v=0
	While time>0
		For i=0 To 255
			SetGamma i,i,i,i-v,i-v,i-v
		Next
		UpdateGamma()
		time=time-dt
		v=v+1
	Wend
End Function