Refactored version of https://gist.github.com/mgwidmann/4edfbae64a883fb77d3d

ElmDemoRefactored.elm

module ElmDemoRefactored where

import Graphics.Element exposing (..)
import Graphics.Collage exposing (..)
import Color exposing (..)
import Time
import Text
import Window

-- MODEL
type alias Model = {count : Int, dir : Int}

-- UPDATE
update: Float -> Model -> Model
update timestamp circleSize =
  let
    newCount = nextCount circleSize.dir circleSize
    newDir = if newCount == 0 then circleSize.dir * -1 else circleSize.dir
    finalCount = if newDir /= circleSize.dir then nextCount newDir circleSize else newCount
  in
    { circleSize | count = finalCount, dir = newDir}

nextCount: Int -> Model -> Int
nextCount dir circleSize =
  rem (circleSize.count + dir) 500

-- VIEW
view: (Int, Int) -> Model -> Element
view (x, y) circleSize =
  collage x y [
    Graphics.Collage.circle (toFloat circleSize.count)
      |> gradient circleGradient,
    scale (toFloat circleSize.count * 0.08) (text (Text.fromString "Elm"))
  ]

circleGradient : Gradient
circleGradient =
  radial (0,0) 0 (0,0) 500
    [ (0, rgb 167 211 12)
    , (1, rgb 1 159 98)
    ]

-- SIGNALS
signals : Signal Time.Time
signals =
  Time.every Time.millisecond

-- MAIN
foldp: Signal Model
foldp =
  Signal.foldp update {count = 0, dir = 1} signals

main : Signal Element
main =
  Signal.map2 view Window.dimensions foldp