Default
  #x = 80

Label
  #message = [kind: "div" contains: #x]

Button Example
  #html/app = [
    root: "mech-root" 
    contains: [
      [kind: "div" contains: [
        [#message]
        [type: "slider" 
          min: 0.0
          max: 100.0
          value: [#x]]
      ]]
    ]
  ]