get("#501") -- triangleness (optimized)
get("#495") -- docrop2

function calc()
  return triangleness(docrop2(lastimg1)) > triangleness(docrop2(lastimg2))
end

return function()
  if mod == nil and solution then
    mod = calc() == solution
  end
  lastimg1, lastimg2 = img1, img2
  return calc() == mod
end