diff --git a/revealjs/_assets/reveal.js b/revealjs/_assets/reveal.js
index 0b3e783..33bed47 160000
--- a/revealjs/_assets/reveal.js
+++ b/revealjs/_assets/reveal.js
@@ -1 +1 @@
-Subproject commit 0b3e7839ebf4ed8b6c180aca0abafa28c67aee6d
+Subproject commit 33bed47daca3f08c396215415e6ece005970734a
diff --git a/revealjs/_templates/index.html.j2 b/revealjs/_templates/index.html.j2
index 7fad4e8..f29d270 100644
--- a/revealjs/_templates/index.html.j2
+++ b/revealjs/_templates/index.html.j2
@@ -22,7 +22,6 @@
         {{ content }}
       </div>
     </div>
-    <script src="../_assets/reveal.js/lib/js/head.min.js"></script>
     <script src="../_assets/reveal.js/js/reveal.js"></script>
     <script>
       Reveal.initialize({
diff --git a/revealjs/alternative_energy/2-geothermie.md b/revealjs/alternative_energy/2-geothermie.md
index 2886b4b..788396e 100644
--- a/revealjs/alternative_energy/2-geothermie.md
+++ b/revealjs/alternative_energy/2-geothermie.md
@@ -40,7 +40,7 @@ background-image="img/island_geothermie.jpg"
 </notes>
 
 ---
-background-image="img/geothermie.svg" background-size="90vmin" background-color="white"
+background-image="img/geothermie.svg" background-size="90vmin" background-color="#ffffff"
 
 <h2 style="position: fixed; top: 0px; left: 0px; right: 0px;">Funktionsweise</h2>
 
diff --git a/revealjs/alternative_energy/3-biogas.md b/revealjs/alternative_energy/3-biogas.md
index da891da..7a0b3f0 100644
--- a/revealjs/alternative_energy/3-biogas.md
+++ b/revealjs/alternative_energy/3-biogas.md
@@ -7,7 +7,7 @@ background-image="img/biogas.jpg"
 </notes>
 
 ---
-background-image="img/biogas_funktion.png" background-size="contain" background-color="white"
+background-image="img/biogas_funktion.png" background-size="contain" background-color="#ffffff"
 
 <h2 style="position: fixed; top: 0px; left: 0px; right: 450px;">Funktionsweise</h2>
 
diff --git a/revealjs/alternative_energy/5-dyson-sphere.md b/revealjs/alternative_energy/5-dyson-sphere.md
index 1bc3d67..1f1a6c1 100644
--- a/revealjs/alternative_energy/5-dyson-sphere.md
+++ b/revealjs/alternative_energy/5-dyson-sphere.md
@@ -10,7 +10,7 @@ background-image="img/dyson-sphere-mirror.svg" background-size="90vmin"
 </notes>
 
 ---
-background-image="img/dyson-sphere-diagram.svg" background-size="90vmin" background-color="white"
+background-image="img/dyson-sphere-diagram.svg" background-size="90vmin" background-color="#ffffff"
 
 <h2 style="position: fixed; top: 0px;">Dyson-Hülle</h2>
 
@@ -80,7 +80,7 @@ Veröffentlicht als *Search for Artificial Stellar Sources of Infrared Radiation
 </notes>
 
 ---
-background-image="img/smbh.svg" background-size="90vmin" background-color="white"
+background-image="img/smbh.svg" background-size="90vmin" background-color="#ffffff"
 
 ## Spiegel um Schwarzes Loch
 
diff --git a/revealjs/information-technology/1-history.md b/revealjs/information-technology/1-history.md
index 745d7f8..1c29430 100644
--- a/revealjs/information-technology/1-history.md
+++ b/revealjs/information-technology/1-history.md
@@ -24,7 +24,7 @@ background-image="img/mainframe.svg"
 </notes>
 
 ---
-background-image="img/packet-switching.svg" background-color="white"
+background-image="img/packet-switching.svg" background-color="#ffffff"
 
 ## Packet switching
 
@@ -38,7 +38,7 @@ background-image="img/packet-switching.svg" background-color="white"
 </notes>
 
 ---
-background-image="img/tcpip.svg" background-color="white"
+background-image="img/tcpip.svg" background-color="#ffffff"
 
 ## TCP/IP
 
@@ -60,7 +60,7 @@ background-image="img/email.jpg"
 </notes>
 
 ---
-background-image="img/www.svg" background-color="white"
+background-image="img/www.svg" background-color="#ffffff"
 
 <h2 style="transform: translateY(-340px);">World Wide Web</h2>
 
diff --git a/revealjs/information-technology/3-companies.md b/revealjs/information-technology/3-companies.md
index 1fa2fdc..5a88813 100644
--- a/revealjs/information-technology/3-companies.md
+++ b/revealjs/information-technology/3-companies.md
@@ -10,7 +10,7 @@ background-image="img/franz/gears.jpg"
 </notes>
 
 ---
-background-image="img/franz/google.png" background-color="white"
+background-image="img/franz/google.png" background-color="#ffffff"
 
 <notes>
  * **advertisement** at the top of search results (“sponsored links”)
@@ -65,7 +65,7 @@ background-image="img/franz/crowd_photo.jpg"
 </notes>
 
 ---
-background-image="img/franz/music.jpg" background-color="white"
+background-image="img/franz/music.jpg" background-color="#ffffff"
 
 <h2 style="transform: translateX(-400px);">Spotify</h2>
 
diff --git a/revealjs/snowden/2-das-handeln.md b/revealjs/snowden/2-das-handeln.md
index 9e1ecc8..b46c02a 100644
--- a/revealjs/snowden/2-das-handeln.md
+++ b/revealjs/snowden/2-das-handeln.md
@@ -20,7 +20,7 @@ background-image="img/kurs.jpg"
 </notes>
 
 ---
-slide background-image="img/copy.jpg" background-color="white"
+slide background-image="img/copy.jpg" background-color="#ffffff"
 
 ## Entwendung
 
@@ -34,7 +34,7 @@ slide background-image="img/copy.jpg" background-color="white"
 </notes>
 
 ---
-slide background-video="img/rsync.mp4" background-size="contain" background-color="black"
+slide background-video="img/rsync.mp4" background-size="contain" background-color="#ffffff"
 
 ## Kommunikation
 
diff --git a/revealjs/snowden/3-was-kann-ich-tun.md b/revealjs/snowden/3-was-kann-ich-tun.md
index fdf5653..2a999df 100644
--- a/revealjs/snowden/3-was-kann-ich-tun.md
+++ b/revealjs/snowden/3-was-kann-ich-tun.md
@@ -6,7 +6,7 @@
 </notes>
 
 ---
-background-image="img/web-protect.png" background-color="white"
+background-image="img/web-protect.png" background-color="#ffffff"
 
 <notes>
  * einfach: Auf verschlüsselte (https-)Verbindung achten
@@ -17,7 +17,7 @@ background-image="img/web-protect.png" background-color="white"
 </notes>
 
 ---
-background-image="img/privacy.jpg" background-color="white"
+background-image="img/privacy.jpg" background-color="#ffffff"
 
 ## Kostenlos
 
@@ -50,7 +50,7 @@ Inc.</small>
 </notes>
 
 ---
-background-image="img/smarthome.jpg" background-color="white"
+background-image="img/smarthome.jpg" background-color="#ffffff"
 
 ## Smart Home