Opacity fade in and out with marks

[Juanluis Vich]

oh! I didn’t know it could be so tricky! nevermind, the last setup you wrote is super handy too, infinite thanks!

[Marcelo Cabral]

Dan, thank you so much for open our eyes and show us how easy could be working with expressions to make our work so easy and moreover for your time and patient. Awesome, you rock man!!!