use "canvasfx"

steps = 20
size = 25
w = steps * (size * 1.25)
h = size * 1.5

step = 1.0 / steps

window("JavaFX Global Alpha example", w, h)

setFill(Color.RED)
y = size * 0.25
for a = 0, a <= 1.0, a += step {
  setGlobalAlpha(a)
  fillRect(a * w, y, size, size)
}