frame.resize 800x400
frame.select background
layer.fill #fff
frame.select drawing
brush:color #000000
brush:size 3
brush.clear
brush.add 0,0
brush.add 1,1
brush.add -1,-1
brush.add 0,0 mirror_x=400
brush.add 1,1 mirror_x=400
brush.add -1,-1 mirror_x=400