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Gui +AlwaysOnTop +ToolWindow +LastFound +E0x20 -Caption
Gui, Color, 0, 0
Gui, Show, x0 y0 w%A_ScreenWidth% h%A_ScreenHeight% na
id:=winexist()
WinSet, Transparent, 0,ahk_id %id% ;set default
c:=0, d:=0
SetFormat,float,0.0

^NumpadAdd::
If c between 0 and 255
{
  If d!=255
  {
    Gui, Color, white, white
    c+=5, d+=5
    WinSet, Transparent, %d%,ahk_id %id%
    traytip,,% d*100/255 "%"
  }
}
Else If c between -255 and 0
{
  If d!=0
  {
    c+=5, d-=5
    WinSet, Transparent, %d%,ahk_id %id%
    traytip,,% "-" d*100/255 "%"
  }
}
Return

^NumpadSub::
If c between 1 and 255
{
  If d!=0
  {
  c-=5, d-=5
  WinSet, Transparent, %d%,ahk_id %id%
  traytip,,% d*100/255 "%"
  }
}
Else If c between -255 and 0
{
  If d!=255
  {
    Gui, Color, 0, 0
    c-=5, d+=5
    WinSet, Transparent, %d%,ahk_id %id%
    traytip,,% "-" d*100/255 "%"
  }
}
Return

file = %A_ScriptDir%\dot.png
If !FileExist(file)
{ URLDownloadToFile, http://www.autohotkey.net/~Micahs/test/dot.png, dot.png
}

Gui -Caption +AlwaysOnTop +ToolWindow +E0x20 +LastFound
Gui, Color, 0xDFDFDF
WinSet, TransColor, 0xDFDFDF 100
Gui, Add, Picture, AltSubmit BackgroundTrans x0 y0 w%A_ScreenWidth% h%A_ScreenHeight%, %file%
Gui, Show, x0 y0 w%A_ScreenWidth% h%A_ScreenHeight% NA

Return

Esc::ExitApp