diff --git a/js/interface.js b/js/interface.js
index 78c6be1..22eeda3 100644
--- a/js/interface.js
+++ b/js/interface.js
@@ -3,7 +3,7 @@
  */
 function Interface() {
 
-  var self = this;
+  let self = this;
 
   // Event Objects for callbacks
   self.events = {};
@@ -28,20 +28,20 @@ function Interface() {
   self.message = document.querySelector('#message');
 
   // add click events
-  self.restartButton.addEventListener("click", function() {
+  self.restartButton.addEventListener("click", function () {
     if (!this.classList.contains('disabled')) {
       self.fireEvent("restart");
     }
   });
 
-  self.pointsButton.addEventListener("click", function() {
+  self.pointsButton.addEventListener("click", function () {
     if (self.playing && !this.classList.contains('disabled')) {
       self.fireEvent("takePoints");
     }
   });
 
 
-  self.dicesButton.addEventListener("click", function() {
+  self.dicesButton.addEventListener("click", function () {
     if (self.playing && !this.classList.contains('disabled')) {
       self.fireEvent("addPoints");
       self.fireEvent("rollDices");
@@ -49,10 +49,10 @@ function Interface() {
   });
 
   // add click events for dices
-  for (var diceIndex = 0; diceIndex < 6; diceIndex++) {
-    var diceContainer = self.dices[diceIndex];
+  for (let diceIndex = 0; diceIndex < 6; diceIndex++) {
+    let diceContainer = self.dices[diceIndex];
     diceContainer.diceIndex = diceIndex;
-    diceContainer.addEventListener("click", function() {
+    diceContainer.addEventListener("click", function () {
       if (self.playing && !this.classList.contains('disabled')) {
         self.fireEvent("toggleDice", this.diceIndex);
       }
@@ -65,7 +65,7 @@ function Interface() {
 /**
  * setup init state
  */
-Interface.prototype.setup = function() {
+Interface.prototype.setup = function () {
   this.dicesButton.classList.add("disabled");
   this.pointsButton.classList.add("disabled");
   this.message.classList.remove('visible');
@@ -75,7 +75,7 @@ Interface.prototype.setup = function() {
 /**
  * register callbacks for events
  */
-Interface.prototype.on = function(event, callback) {
+Interface.prototype.on = function (event, callback) {
   if (!this.events[event]) {
     this.events[event] = [];
   }
@@ -85,10 +85,10 @@ Interface.prototype.on = function(event, callback) {
 /**
  * fire events and execute callbacks
  */
-Interface.prototype.fireEvent = function(event, data) {
-  var callbacks = this.events[event];
+Interface.prototype.fireEvent = function (event, data) {
+  let callbacks = this.events[event];
   if (callbacks) {
-    callbacks.forEach(function(callback) {
+    callbacks.forEach(function (callback) {
       callback(data);
     });
   }
@@ -97,12 +97,12 @@ Interface.prototype.fireEvent = function(event, data) {
 /**
  * Set dices
  */
-Interface.prototype.setDices = function(dices) {
-  var self = this;
+Interface.prototype.setDices = function (dices) {
+  let self = this;
 
-  for (var diceIndex = 0; diceIndex < 6; diceIndex++) {
-    var dice = dices[diceIndex];
-    var diceContainer = self.dices[diceIndex];
+  for (let diceIndex = 0; diceIndex < 6; diceIndex++) {
+    let dice = dices[diceIndex];
+    let diceContainer = self.dices[diceIndex];
     diceContainer.innerHTML = dice.value + 1;
 
     if (dice.disabled) {
@@ -129,18 +129,18 @@ Interface.prototype.setDices = function(dices) {
 /**
  * fire dices animation
  */
-Interface.prototype.animateDices = function(dices, timeout, callback) {
-  var self = this;
-  for (var diceIndex = 0; diceIndex < 6; diceIndex++) {
-    var dice = dices[diceIndex];
+Interface.prototype.animateDices = function (dices, timeout, callback) {
+  let self = this;
+  for (let diceIndex = 0; diceIndex < 6; diceIndex++) {
+    let dice = dices[diceIndex];
     if (!dice.disabled && !dice.selected) {
       self.dices[diceIndex].classList.add("animate");
       self.dices[diceIndex].classList.add("duration" + diceIndex);
     }
   }
 
-  setTimeout(function() {
-    for (var diceIndex = 0; diceIndex < 6; diceIndex++) {
+  setTimeout(function () {
+    for (let diceIndex = 0; diceIndex < 6; diceIndex++) {
       self.dices[diceIndex].classList.remove("animate");
     }
     if (callback) {
@@ -152,7 +152,7 @@ Interface.prototype.animateDices = function(dices, timeout, callback) {
 /**
  * set disabled state of 'restart' button
  */
-Interface.prototype.disableRestart = function(disabled) {
+Interface.prototype.disableRestart = function (disabled) {
   if (disabled) {
     this.restartButton.classList.add("disabled")
   } else {
@@ -163,7 +163,7 @@ Interface.prototype.disableRestart = function(disabled) {
 /**
  * set disabled state of 'take points' button
  */
-Interface.prototype.disableTakePoints = function(disabled) {
+Interface.prototype.disableTakePoints = function (disabled) {
   if (disabled) {
     this.pointsButton.classList.add("disabled")
   } else {
@@ -174,7 +174,7 @@ Interface.prototype.disableTakePoints = function(disabled) {
 /**
  * set disabled state of 'roll dices' button
  */
-Interface.prototype.disableRollDices = function(disabled) {
+Interface.prototype.disableRollDices = function (disabled) {
   if (disabled) {
     this.dicesButton.classList.add("disabled")
   } else {
@@ -185,14 +185,14 @@ Interface.prototype.disableRollDices = function(disabled) {
 /**
  * set points
  */
-Interface.prototype.setPoints = function(points) {
+Interface.prototype.setPoints = function (points) {
   this.points.innerHTML = points;
 };
 
 /**
  * set playing status (Player or CPU)
  */
-Interface.prototype.setPlaying = function(playing) {
+Interface.prototype.setPlaying = function (playing) {
   if (playing) {
     this.playing = true;
     this.playerScoreContainer.classList.add('active');
@@ -207,10 +207,10 @@ Interface.prototype.setPlaying = function(playing) {
 /**
  * set player data
  */
-Interface.prototype.setPlayer = function(player) {
+Interface.prototype.setPlayer = function (player) {
   this.playerScore.innerHTML = player.score;
-  var zilchs = '';
-  for (var i = 0; i < player.zilch; i++) {
+  let zilchs = '';
+  for (let i = 0; i < player.zilch; i++) {
     zilchs += '<div class="point"></div>';
   }
   this.playerZilch.innerHTML = zilchs;
@@ -220,10 +220,10 @@ Interface.prototype.setPlayer = function(player) {
 /**
  * set cpu data
  */
-Interface.prototype.setCpu = function(cpu) {
+Interface.prototype.setCpu = function (cpu) {
   this.cpuScore.innerHTML = cpu.score;
-  var zilchs = '';
-  for (var i = 0; i < cpu.zilch; i++) {
+  let zilchs = '';
+  for (let i = 0; i < cpu.zilch; i++) {
     zilchs += '<div class="point"></div>';
   }
 
@@ -233,15 +233,15 @@ Interface.prototype.setCpu = function(cpu) {
 /**
  * show message with timeout and callback
  */
-Interface.prototype.showMessage = function(message, timeout, callback) {
-  var self = this;
+Interface.prototype.showMessage = function (message, timeout, callback) {
+  let self = this;
 
   self.message.innerHTML = '<p>' + message + '</p>';
 
   self.message.classList.add('visible');
 
   if (timeout) {
-    setTimeout(function() {
+    setTimeout(function () {
       self.clearMessage(callback);
     }, timeout);
   } else if (callback) {
@@ -252,9 +252,9 @@ Interface.prototype.showMessage = function(message, timeout, callback) {
 /**
  * hide current message
  */
-Interface.prototype.clearMessage = function(callback) {
+Interface.prototype.clearMessage = function (callback) {
   this.message.classList.remove('visible');
   if (callback) {
     callback();
   }
-};
+};
\ No newline at end of file