diff --git a/app/scripts/App.js b/app/scripts/App.js
index 79bbd2c..a3fdd68 100644
--- a/app/scripts/App.js
+++ b/app/scripts/App.js
@@ -11,8 +11,7 @@ import PitchStatisticService from "./services/pitch_statistic_service.js";
 import RhythmStatisticService from "./services/rhythm_statistic_service.js";
 import AnalyticsService from "./services/analytics_service.js";
 import AppFreezer from "./AppFreezer.js";
-import { Nav, NavItem, Button, Input } from "react-bootstrap";
-import classNames from "classnames";
+import { Nav, NavItem } from "react-bootstrap";
 
 const pianoBackgroundJpg = require("file!../images/piano-background.jpg");
 
diff --git a/app/scripts/services/analytics_service.js b/app/scripts/services/analytics_service.js
index 981695b..f4a3ca7 100644
--- a/app/scripts/services/analytics_service.js
+++ b/app/scripts/services/analytics_service.js
@@ -1,3 +1,4 @@
+/* global ga */
 export default {
   sendEvent: function(eventCategory, eventAction, eventValue) {
     if (window.location.hostname === "localhost" || typeof ga === "undefined") {
diff --git a/app/scripts/services/bar_generator.js b/app/scripts/services/bar_generator.js
index 5146d19..1a2a17a 100644
--- a/app/scripts/services/bar_generator.js
+++ b/app/scripts/services/bar_generator.js
@@ -146,7 +146,7 @@ export default {
     const onePerTime = !isMidiAvailable;
 
     const [trebleNotes, bassNotes] = _.unzip(
-      _.range(0, options.chordsPerBar).map(index => {
+      _.range(0, options.chordsPerBar).map(() => {
         const generatePossibleNotes = clef => {
           if (level) {
             return {
diff --git a/app/scripts/services/key_converter.js b/app/scripts/services/key_converter.js
index 481cebc..8d3c5ea 100644
--- a/app/scripts/services/key_converter.js
+++ b/app/scripts/services/key_converter.js
@@ -44,17 +44,17 @@ function initializeKeyMap() {
     .concat(_.flatten(_.times(octaveCount, () => octaveNotes)))
     .concat([octaveNotes[0]]);
 
-  const keyMap = {};
+  const newKeyMap = {};
 
   for (let index = 0, key; index < claviature.length; index++) {
     key = claviature[index];
     const offsettedIndex = index + claviatureOffset;
     const nr = Math.floor((offsettedIndex + octaveNoteLength) / octaveNoteLength);
 
-    keyMap[index + 21] = key + "/" + nr;
+    newKeyMap[index + 21] = key + "/" + nr;
   }
 
-  return keyMap;
+  return newKeyMap;
 }
 
 const KeyConverter = {
diff --git a/app/scripts/services/level_service.js b/app/scripts/services/level_service.js
index 44016ec..169db1e 100644
--- a/app/scripts/services/level_service.js
+++ b/app/scripts/services/level_service.js
@@ -61,8 +61,8 @@ const LevelService = {
   },
   getAllNotesUntilLevelIndex(levelIndex, optClef) {
     return _.flatten(
-      _.range(levelIndex).map(levelIndex => {
-        const keys = Levels[levelIndex].keys;
+      _.range(levelIndex).map(index => {
+        const keys = Levels[index].keys;
         if (optClef) {
           return keys[optClef];
         }
diff --git a/app/scripts/services/metronome_service.js b/app/scripts/services/metronome_service.js
index 12fa8d2..3b45888 100644
--- a/app/scripts/services/metronome_service.js
+++ b/app/scripts/services/metronome_service.js
@@ -1,5 +1,3 @@
-import _ from "lodash";
-
 const successMp3Url = require("file!../../resources/success.mp3");
 const audioCtx = new (window.AudioContext || window.webkitAudioContext)();
 let audioBuffer;
@@ -18,7 +16,7 @@ function loadMp3() {
         audioBuffer = buffer;
       },
       function(e) {
-        "Error with decoding audio data" + e.err;
+        console.error("Error with decoding audio data" + e.err);
       }
     );
   };
@@ -38,8 +36,9 @@ export default {
   play: function(delay) {
     const source = this.createAudioNode();
     source.start(audioCtx.currentTime + delay / 1000);
+    return source;
   },
-  stop: function() {
+  stop: function(source) {
     source.stop(0);
   }
 };
diff --git a/app/scripts/services/rhythm_checker.js b/app/scripts/services/rhythm_checker.js
index 7120c96..0577cb2 100644
--- a/app/scripts/services/rhythm_checker.js
+++ b/app/scripts/services/rhythm_checker.js
@@ -1,5 +1,3 @@
-import _ from "lodash";
-
 export default {
   convertDurationsToTimes: function(durations, barDuration) {
     const times = [];
@@ -69,7 +67,7 @@ export default {
 
     if (givenTimes.length > expectedTimes.length) {
       beatEvaluations = beatEvaluations.concat(
-        givenTimes.slice(expectedTimes.length).map(el => ({ superfluous: true, correct: false }))
+        givenTimes.slice(expectedTimes.length).map(() => ({ superfluous: true, correct: false }))
       );
     }
 
diff --git a/app/scripts/services/rhythm_statistic_service.js b/app/scripts/services/rhythm_statistic_service.js
index e2d956e..bdf829b 100644
--- a/app/scripts/services/rhythm_statistic_service.js
+++ b/app/scripts/services/rhythm_statistic_service.js
@@ -14,7 +14,7 @@ class RhythmStatisticService {
 
   off(event, callback) {
     if (callback) {
-      this.callbacks = this.callbacks.filter(el => el != callback);
+      this.callbacks = this.callbacks.filter(el => el !== callback);
     } else {
       this.callbacks = [];
     }
diff --git a/app/scripts/services/stat_evolver.js b/app/scripts/services/stat_evolver.js
index 8212578..282886a 100644
--- a/app/scripts/services/stat_evolver.js
+++ b/app/scripts/services/stat_evolver.js
@@ -1,3 +1,4 @@
+import _ from "lodash";
 // Runs evolutions on statistic objects, so that we can update the schema
 
 const evolutions = [
diff --git a/app/scripts/views/animated_number.js b/app/scripts/views/animated_number.js
index d4dd867..294ebc8 100644
--- a/app/scripts/views/animated_number.js
+++ b/app/scripts/views/animated_number.js
@@ -2,6 +2,10 @@ import React, { Component } from "react";
 import { Motion, spring } from "react-motion";
 
 export default class AnimatedNumber extends Component {
+  static propTypes = {
+    formatter: React.PropTypes.func,
+    number: React.PropTypes.number
+  };
   render() {
     const formatter = this.props.formatter;
     const number = this.props.number;
diff --git a/app/scripts/views/beat_visualization.js b/app/scripts/views/beat_visualization.js
index 55bc6ec..ce31ea2 100644
--- a/app/scripts/views/beat_visualization.js
+++ b/app/scripts/views/beat_visualization.js
@@ -5,7 +5,7 @@ import _ from "lodash";
 import RhythmChecker from "../services/rhythm_checker.js";
 
 export default class BeatVisualization extends Component {
-  propTypes: {
+  static propTypes = {
     settings: React.PropTypes.object.isRequired,
     barDuration: React.PropTypes.number.isRequired,
     currentRhythm: React.PropTypes.object.isRequired,
diff --git a/app/scripts/views/claviature_view.js b/app/scripts/views/claviature_view.js
index e042745..f101a46 100644
--- a/app/scripts/views/claviature_view.js
+++ b/app/scripts/views/claviature_view.js
@@ -3,7 +3,7 @@ import KeyConverter from "../services/key_converter.js";
 import classNames from "classnames";
 
 export default class ClaviatureView extends Component {
-  propTypes: {
+  static propTypes = {
     desiredKeys: React.PropTypes.array,
     keySignature: React.PropTypes.string,
     successCallback: React.PropTypes.func,
diff --git a/app/scripts/views/collapsable_container.js b/app/scripts/views/collapsable_container.js
index aa78743..5b022e1 100644
--- a/app/scripts/views/collapsable_container.js
+++ b/app/scripts/views/collapsable_container.js
@@ -3,7 +3,8 @@ import classNames from "classnames";
 import _ from "lodash";
 
 export default class BeatVisualization extends Component {
-  propTypes: {
+  static propTypes = {
+    children: React.PropTypes.node,
     collapsed: React.PropTypes.bool.isRequired,
     maxHeight: React.PropTypes.number,
     freeze: React.PropTypes.bool,
diff --git a/app/scripts/views/game_button.js b/app/scripts/views/game_button.js
index 611bc92..b41bb44 100644
--- a/app/scripts/views/game_button.js
+++ b/app/scripts/views/game_button.js
@@ -1,10 +1,8 @@
 import React, { Component } from "react";
-import classNames from "classnames";
-import _ from "lodash";
-import { Button, ButtonToolbar } from "react-bootstrap";
+import { Button } from "react-bootstrap";
 
 export default class GameButton extends Component {
-  propTypes: {
+  static propTypes = {
     label: React.PropTypes.string.isRequired,
     onClick: React.PropTypes.func.isRequired,
     primary: React.PropTypes.bool,
@@ -21,16 +19,15 @@ export default class GameButton extends Component {
         return;
       }
 
-      if (this.props.shortcutLetter === undefined) {
+      if (!this.props.shortcutLetter) {
         return;
       }
       const isPrimaryAndEnter = this.props.primary && event.code === "Enter";
       const charCode = event.which || event.keyCode;
       const isShortcutLetter = String.fromCharCode(charCode) === this.props.shortcutLetter;
       if (isPrimaryAndEnter || isShortcutLetter) {
-        return this.props.onClick();
+        this.props.onClick();
       }
-      return false;
     };
 
     document.addEventListener("keypress", this.keyHandler);
diff --git a/app/scripts/views/level_view.js b/app/scripts/views/level_view.js
index de9545d..b13eed3 100644
--- a/app/scripts/views/level_view.js
+++ b/app/scripts/views/level_view.js
@@ -1,11 +1,10 @@
-import Chartist from "Chartist";
+import _ from "lodash";
 import React, { Component } from "react";
-import { Tooltip, OverlayTrigger } from "react-bootstrap";
 import LevelService from "../services/level_service.js";
 import PieChart from "../views/pie_chart.js";
 
 export default class LevelView extends Component {
-  propTypes: {
+  static propTypes = {
     statisticService: React.PropTypes.object.isRequired
   };
 
diff --git a/app/scripts/views/metronome_view.js b/app/scripts/views/metronome_view.js
index 05bc8f3..3adbf8b 100644
--- a/app/scripts/views/metronome_view.js
+++ b/app/scripts/views/metronome_view.js
@@ -6,7 +6,8 @@ import MetronomeService from "../services/metronome_service.js";
 import CollapsableContainer from "./collapsable_container.js";
 
 export default class MetronomeView extends Component {
-  propTypes: {
+  static propTypes = {
+    onMetronomeEnded: React.PropTypes.func,
     settings: React.PropTypes.object.isRequired,
     statisticService: React.PropTypes.object.isRequired
   };
@@ -59,7 +60,7 @@ export default class MetronomeView extends Component {
   render() {
     return (
       <CollapsableContainer
-        collapsed={this.state.currentMetronomeBeat == -1}
+        collapsed={this.state.currentMetronomeBeat === -1}
         className={classNames({
           opacityOut: (this.state.currentMetronomeBeat + 1) % 4 === 0
         })}
diff --git a/app/scripts/views/newsletter_form.js b/app/scripts/views/newsletter_form.js
index a5c55e6..b741216 100644
--- a/app/scripts/views/newsletter_form.js
+++ b/app/scripts/views/newsletter_form.js
@@ -1,5 +1,4 @@
 import React, { Component } from "react";
-import { Input } from "react-bootstrap";
 
 export default class NewsLetterForm extends Component {
   componentDidMount() {
diff --git a/app/scripts/views/pie_chart.js b/app/scripts/views/pie_chart.js
index 07a4d7d..5f24d3e 100644
--- a/app/scripts/views/pie_chart.js
+++ b/app/scripts/views/pie_chart.js
@@ -3,7 +3,7 @@ import React, { Component } from "react";
 import PureRenderMixin from "react-addons-pure-render-mixin";
 
 export default class LevelView extends Component {
-  propTypes: {
+  static propTypes = {
     pieParts: React.PropTypes.array.isRequired
   };
 
diff --git a/app/scripts/views/pitch_reading_view.js b/app/scripts/views/pitch_reading_view.js
index 172dc75..e5f145e 100644
--- a/app/scripts/views/pitch_reading_view.js
+++ b/app/scripts/views/pitch_reading_view.js
@@ -16,7 +16,7 @@ import CollapsableContainer from "./collapsable_container.js";
 const successMp3Url = require("file!../../resources/success.mp3");
 
 export default class PitchReadingView extends Component {
-  propTypes: {
+  static propTypes = {
     statisticService: React.PropTypes.object.isRequired,
     settings: React.PropTypes.object.isRequired,
     isActive: React.PropTypes.bool.isRequired
diff --git a/app/scripts/views/pitch_settings_view.js b/app/scripts/views/pitch_settings_view.js
index 1e45359..3043eb7 100644
--- a/app/scripts/views/pitch_settings_view.js
+++ b/app/scripts/views/pitch_settings_view.js
@@ -7,6 +7,10 @@ import _ from "lodash";
 import AnalyticsService from "../services/analytics_service.js";
 
 export default class PitchSettingsView extends Component {
+  static propTypes = {
+    settings: React.PropTypes.object
+  };
+
   constructor(props, context) {
     super(props, context);
   }
@@ -37,8 +41,8 @@ export default class PitchSettingsView extends Component {
     };
   }
 
-  onMidiSelectChange(event) {
-    AppFreezer.trigger("input:changed", parseInt(this.refs.midiSelect.value));
+  onMidiSelectChange() {
+    AppFreezer.trigger("input:changed", parseInt(this.refs.midiSelect.value, 10));
   }
 
   render() {
diff --git a/app/scripts/views/pitch_statistic_view.js b/app/scripts/views/pitch_statistic_view.js
index 4e5e382..3d9618e 100644
--- a/app/scripts/views/pitch_statistic_view.js
+++ b/app/scripts/views/pitch_statistic_view.js
@@ -8,7 +8,7 @@ import AnimatedNumber from "./animated_number.js";
 import StarAnimation from "./star_animation.js";
 
 export default class PitchStatisticView extends Component {
-  propTypes: {
+  static propTypes = {
     statisticService: React.PropTypes.object.isRequired,
     settings: React.PropTypes.object.isRequired
   };
diff --git a/app/scripts/views/privacy_policy_modal.js b/app/scripts/views/privacy_policy_modal.js
index d6e0026..6bb551e 100644
--- a/app/scripts/views/privacy_policy_modal.js
+++ b/app/scripts/views/privacy_policy_modal.js
@@ -2,6 +2,10 @@ import React, { Component } from "react";
 import { Modal, Button } from "react-bootstrap";
 
 export default class PrivacyPolicyModal extends Component {
+  static propTypes = {
+    onHide: React.PropTypes.func.isRequired
+  };
+
   render() {
     return (
       <Modal {...this.props} bsSize="large" aria-labelledby="contained-modal-title-lg">
diff --git a/app/scripts/views/range_setting_component.js b/app/scripts/views/range_setting_component.js
index b1ae609..48794d7 100644
--- a/app/scripts/views/range_setting_component.js
+++ b/app/scripts/views/range_setting_component.js
@@ -11,7 +11,7 @@ export default class SettingsView extends Component {
     label: ""
   };
 
-  propTypes: {
+  static propTypes = {
     rangeMin: PropTypes.number.isRequired,
     rangeMax: PropTypes.number.isRequired,
     values: PropTypes.array,
diff --git a/app/scripts/views/rhythm_reading_view.js b/app/scripts/views/rhythm_reading_view.js
index 376cf55..536ba5b 100644
--- a/app/scripts/views/rhythm_reading_view.js
+++ b/app/scripts/views/rhythm_reading_view.js
@@ -1,10 +1,8 @@
 import React, { Component } from "react";
 import classNames from "classnames";
-import _ from "lodash";
 
 import BarGenerator from "../services/bar_generator.js";
 import RhythmChecker from "../services/rhythm_checker.js";
-import MetronomeService from "../services/metronome_service.js";
 import AnalyticsService from "../services/analytics_service.js";
 
 import StaveRenderer from "./stave_renderer.js";
@@ -25,7 +23,7 @@ const Phases = {
 };
 
 export default class RhythmReadingView extends Component {
-  propTypes: {
+  static propTypes = {
     settings: React.PropTypes.object.isRequired,
     statisticService: React.PropTypes.object.isRequired,
     isActive: React.PropTypes.bool.isRequired
@@ -204,10 +202,6 @@ export default class RhythmReadingView extends Component {
   }
 
   render() {
-    const messageContainerClasses = classNames({
-      hide: this.state.errorMessage === null
-    });
-
     const welcomeText = (
       <CollapsableContainer collapsed={this.state.phase !== Phases.welcome}>
         <h3>Welcome to this rhythm training!</h3>
diff --git a/app/scripts/views/rhythm_settings_view.js b/app/scripts/views/rhythm_settings_view.js
index 94c1a48..dfcac1a 100644
--- a/app/scripts/views/rhythm_settings_view.js
+++ b/app/scripts/views/rhythm_settings_view.js
@@ -2,12 +2,14 @@ import React, { Component } from "react";
 import PureRenderMixin from "react-addons-pure-render-mixin";
 import RangeSettingComponent from "./range_setting_component";
 import SettingLine from "./setting_line";
-import KeyConverter from "../services/key_converter";
-import AppFreezer from "../AppFreezer.js";
 import AnalyticsService from "../services/analytics_service.js";
 import _ from "lodash";
 
 export default class PitchSettingsView extends Component {
+  static propTypes = {
+    settings: React.PropTypes.object
+  };
+
   constructor(props, context) {
     super(props, context);
     this.shouldComponentUpdate = PureRenderMixin.shouldComponentUpdate.bind(this);
diff --git a/app/scripts/views/rhythm_statistic_view.js b/app/scripts/views/rhythm_statistic_view.js
index 896353e..e6a71e9 100644
--- a/app/scripts/views/rhythm_statistic_view.js
+++ b/app/scripts/views/rhythm_statistic_view.js
@@ -1,13 +1,14 @@
 import Chartist from "Chartist";
 import React, { Component } from "react";
 import { Tooltip, OverlayTrigger } from "react-bootstrap";
+import _ from "lodash";
 
 import AnimatedNumber from "./animated_number.js";
 import StarAnimation from "./star_animation.js";
 import PureRenderMixin from "react-addons-pure-render-mixin";
 
 export default class RhythmStatisticView extends Component {
-  propTypes: {
+  static propTypes = {
     statisticService: React.PropTypes.object.isRequired
   };
 
diff --git a/app/scripts/views/setting_line.js b/app/scripts/views/setting_line.js
index 5de21a4..16fc93c 100644
--- a/app/scripts/views/setting_line.js
+++ b/app/scripts/views/setting_line.js
@@ -1,12 +1,12 @@
 import React, { Component, PropTypes } from "react";
-import _ from "lodash";
 
 export default class SettingLine extends Component {
   static defaultProps = {
     label: ""
   };
 
-  propTypes: {
+  static propTypes = {
+    children: PropTypes.node,
     label: PropTypes.string,
     className: PropTypes.string
   };
diff --git a/app/scripts/views/star_animation.js b/app/scripts/views/star_animation.js
index 7cc8ca2..2f678f4 100644
--- a/app/scripts/views/star_animation.js
+++ b/app/scripts/views/star_animation.js
@@ -1,7 +1,10 @@
 import React, { Component } from "react";
-import { Motion, spring } from "react-motion";
 
 export default class StarAnimation extends Component {
+  static propTypes = {
+    number: React.PropTypes.number
+  };
+
   constructor() {
     super();
     this.state = {
diff --git a/app/scripts/views/stave_renderer.js b/app/scripts/views/stave_renderer.js
index 35db0d0..36a2fc5 100644
--- a/app/scripts/views/stave_renderer.js
+++ b/app/scripts/views/stave_renderer.js
@@ -1,6 +1,5 @@
 import Vex from "vexflow";
 import React, { Component } from "react";
-import classNames from "classnames";
 import _ from "lodash";
 import PureRenderMixin from "react-addons-pure-render-mixin";
 
@@ -9,7 +8,7 @@ class StaveRenderer extends Component {
     staveCount: 2
   };
 
-  propTypes: {
+  static propTypes = {
     keys: React.PropTypes.array,
     chordIndex: React.PropTypes.number,
     keySignature: React.PropTypes.string,