m := image.NewRGBA(image.Rect(0, 0, 16, 16))
	for y := 0; y < 16; y++ {
		for x := 0; x < 16; x++ {
			m.Set(x, y, color.RGBA{uint8(x * alpha / 15), 0, 0, uint8(alpha)})
		}
	}
	return m
}

func gradYellow(alpha int) Image {
	m := image.NewRGBA(image.Rect(0, 0, 16, 16))
	for y := 0; y < 16; y++ {
		for x := 0; x < 16; x++ {
			m.Set(x, y, color.RGBA{uint8(x * alpha / 15), uint8(y * alpha / 15), 0, uint8(alpha)})
		}