strange behavior with gradient :angle

[jerry anning]

Try this little demo.

Shoes.app do
  i = 0
  every(1) do
    clear
    background(gradient(cornflowerblue, tomato, :angle => i % 360))
    i += 5
  end
end

As you see, as the angle increases up to 135 degrees, the gradient gets
sharper and sharper. At exactly 135 degrees, the tomato suddenly vanishes
completely. Once past 135 degrees, tomato comes back and the gradient starts
getting fuzzier. This is happening (for me) on windows xp with Shoes .r970.