Div follows mouse example

divmouse.elm

import Html
import Html.Attributes exposing (style)
import Html.Events exposing (on)

import Signal exposing (mailbox)

import Json.Decode exposing (Decoder, (:=), int)


positionDecoder = 
  Json.Decode.object2 (,)
    ("clientX" := int)
    ("clientY" := int)


{address, signal} = mailbox (0,0)

(=>) = (,)

app (x,y) = 
  Html.div 
    []
    [ Html.div 
        [ style 
            [ "position" => "absolute"
            , "width" => "100vw"
            , "height" => "100vh"
            ]
        , on "mousemove" positionDecoder (Signal.message address)
        ]
        []
    , Html.div 
        [ style 
            [ "position" => "absolute"
            , "background-color" => "red"
            , "width" => "50px"
            , "height" => "50px"
            , "transform" => ("translate(" ++ toString (x - 25) ++ "px" ++ "," ++ toString (y - 25) ++ "px)")
            ]
        
        ]
        []
    ]
    
    
main = 
  Signal.map app signal