diff --git a/tikz/arc/arc.tex b/tikz/arc/arc.tex
index 353d9cb..c58d754 100644
--- a/tikz/arc/arc.tex
+++ b/tikz/arc/arc.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/center-line/center-line.tex b/tikz/center-line/center-line.tex
index 0ad3719..947b28d 100644
--- a/tikz/center-line/center-line.tex
+++ b/tikz/center-line/center-line.tex
@@ -4,7 +4,7 @@
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/center-two-cluster/center-two-cluster.tex b/tikz/center-two-cluster/center-two-cluster.tex
index 9812a51..85fe9d5 100644
--- a/tikz/center-two-cluster/center-two-cluster.tex
+++ b/tikz/center-two-cluster/center-two-cluster.tex
@@ -4,7 +4,7 @@
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, shapes, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/center-two-cluster/tikz.py b/tikz/center-two-cluster/tikz.py
index 1708b10..751e7a1 100644
--- a/tikz/center-two-cluster/tikz.py
+++ b/tikz/center-two-cluster/tikz.py
@@ -8,7 +8,7 @@ print """\documentclass{article}
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \\begin{document}
diff --git a/tikz/center/center.tex b/tikz/center/center.tex
index 26fac9b..d2f9722 100644
--- a/tikz/center/center.tex
+++ b/tikz/center/center.tex
@@ -4,7 +4,7 @@
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/missing-square-fibonacci/missing-square-fibonacci.tex b/tikz/missing-square-fibonacci/missing-square-fibonacci.tex
index 239b110..0c70e0f 100644
--- a/tikz/missing-square-fibonacci/missing-square-fibonacci.tex
+++ b/tikz/missing-square-fibonacci/missing-square-fibonacci.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, snakes} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/robots-circle/robots-circle.png b/tikz/robots-circle/robots-circle.png
new file mode 100644
index 0000000..e5c438c
Binary files /dev/null and b/tikz/robots-circle/robots-circle.png differ
diff --git a/tikz/robots-circle/robots-circle.tex b/tikz/robots-circle/robots-circle.tex
index 87a16d1..0da3bb8 100644
--- a/tikz/robots-circle/robots-circle.tex
+++ b/tikz/robots-circle/robots-circle.tex
@@ -4,7 +4,7 @@
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/robots-walk-away/robots-walk-away.png b/tikz/robots-walk-away/robots-walk-away.png
new file mode 100644
index 0000000..e3d5ef1
Binary files /dev/null and b/tikz/robots-walk-away/robots-walk-away.png differ
diff --git a/tikz/robots-walk-away/robots-walk-away.tex b/tikz/robots-walk-away/robots-walk-away.tex
index 0f71bc6..1bbb8e3 100644
--- a/tikz/robots-walk-away/robots-walk-away.tex
+++ b/tikz/robots-walk-away/robots-walk-away.tex
@@ -4,7 +4,7 @@
 \usepackage{tikz}
 \usepackage{tkz-fct}
 \usetikzlibrary{shapes.misc}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/triangle-angles/triangle-angles.png b/tikz/triangle-angles/triangle-angles.png
index d3ac41a..dcd9416 100644
Binary files a/tikz/triangle-angles/triangle-angles.png and b/tikz/triangle-angles/triangle-angles.png differ
diff --git a/tikz/triangle-angles/triangle-angles.tex b/tikz/triangle-angles/triangle-angles.tex
index 8273f6b..2bc3648 100644
--- a/tikz/triangle-angles/triangle-angles.tex
+++ b/tikz/triangle-angles/triangle-angles.tex
@@ -2,7 +2,7 @@
     \usepackage[pdftex,active,tightpage]{preview}
     \setlength\PreviewBorder{2mm}
     \usepackage{tikz}
-    \usetikzlibrary{shapes, calc, shapes,snakes} 
+    \usetikzlibrary{shapes, calc, shapes, decorations} 
     \usepackage{amsmath,amssymb}
 
     \begin{document}
diff --git a/tikz/triangle-heron-tricky/triangle-heron-tricky.tex b/tikz/triangle-heron-tricky/triangle-heron-tricky.tex
index 92bcbc7..94eb63d 100644
--- a/tikz/triangle-heron-tricky/triangle-heron-tricky.tex
+++ b/tikz/triangle-heron-tricky/triangle-heron-tricky.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/triangle/triangle.tex b/tikz/triangle/triangle.tex
index 93d7416..49cbf4e 100644
--- a/tikz/triangle/triangle.tex
+++ b/tikz/triangle/triangle.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes, calc, shapes,snakes} 
+\usetikzlibrary{shapes, calc, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/tut-uebung-vorlesung/Readme.md b/tikz/tut-uebung-vorlesung/Readme.md
new file mode 100644
index 0000000..6116ef5
--- /dev/null
+++ b/tikz/tut-uebung-vorlesung/Readme.md
@@ -0,0 +1,3 @@
+Compiled example
+----------------
+![Example](tut-uebung-vorlesung.png)
diff --git a/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.png b/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.png
new file mode 100644
index 0000000..e5d065e
Binary files /dev/null and b/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.png differ
diff --git a/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.tex b/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.tex
index 82ab4f2..c6d128e 100644
--- a/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.tex
+++ b/tikz/tut-uebung-vorlesung/tut-uebung-vorlesung.tex
@@ -7,7 +7,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes,snakes,calc,patterns} 
+\usetikzlibrary{shapes,decorations,calc,patterns} 
 \usepackage{amsmath,amssymb}
 \begin{document}
 \begin{preview}
diff --git a/tikz/url-structure/url-structure.png b/tikz/url-structure/url-structure.png
index c64a168..9d1f144 100644
Binary files a/tikz/url-structure/url-structure.png and b/tikz/url-structure/url-structure.png differ
diff --git a/tikz/url-structure/url-structure.tex b/tikz/url-structure/url-structure.tex
index fd34448..ccce202 100644
--- a/tikz/url-structure/url-structure.tex
+++ b/tikz/url-structure/url-structure.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes,snakes} 
+\usetikzlibrary{shapes, decorations} 
 \usepackage{amsmath,amssymb}
 
 \begin{document}
diff --git a/tikz/venn-diagramm/venn-diagramm.tex b/tikz/venn-diagramm/venn-diagramm.tex
index 6cc3b2e..31a8506 100644
--- a/tikz/venn-diagramm/venn-diagramm.tex
+++ b/tikz/venn-diagramm/venn-diagramm.tex
@@ -2,7 +2,7 @@
 \usepackage[pdftex,active,tightpage]{preview}
 \setlength\PreviewBorder{2mm}
 \usepackage{tikz}
-\usetikzlibrary{shapes,snakes,calc} 
+\usetikzlibrary{shapes,decorations,calc} 
 \usepackage{amsmath,amssymb}
 \begin{document}
 \begin{preview}