root = Card([header, description, signupForm])
header = CardHeader("The Product Weekly", "One email, every Tuesday")
description = TextContent("Each week you get one short email covering the product launches, changelogs, and design patterns worth your time.")
signupForm = Form("newsletter-signup", formButtons, [emailField])
emailField = FormControl("Email address", emailInput, "No spam, unsubscribe anytime.")
emailInput = Input("email", "you@example.com", "email")
formButtons = Buttons([subscribeBtn])
subscribeBtn = Button("Subscribe", null, "primary")