     scrollFast: React.PropTypes.bool
     onExerciseToggle: React.PropTypes.func.isRequired
 
-  mixins: [ScrollTo]
+  mixins: [ScrollTo, addons.PureRenderMixin]
 
   componentDidMount:   ->
     @scrollToSelector('.exercise-sections', {immediate: @props.scrollFast})

Icon = require '../icon'

SectionsExercises = React.createClass

  propTypes:
    exercises:   React.PropTypes.array.isRequired

  getScrollTopOffset: -> if @props.scrollFast then 110 else 150 # no idea why the difference, sorry :(

  render: ->
    chapter_sections = _.keys @props.exercises.grouped

    <div className="exercise-cards">
      {for cs in chapter_sections
