diff --git a/beamercolorthemeaptero.sty b/beamercolorthemeaptero.sty
index 04980e1..88e9122 100644
--- a/beamercolorthemeaptero.sty
+++ b/beamercolorthemeaptero.sty
@@ -55,13 +55,22 @@
 \setbeamercolor{enumerate subitem}{parent={normal text}}
 
 \setbeamercolor{block title}{fg=white, bg=blue}
-\setbeamercolor{block body}{fg=normal text.fg, bg=black!10}
+\setbeamercolor{block body}{fg=normal text.fg, bg=blue!20}
+\setbeamercolor{block line top}{fg=}
+\setbeamercolor{block line middle}{fg=}
+\setbeamercolor{block line bottom}{fg=}
 
 \setbeamercolor{block title alerted}{parent={block title}, bg=red}
-\setbeamercolor{block body alerted}{parent={block body}, fg=red}
+\setbeamercolor{block body alerted}{fg=red, bg=red!15}
+\setbeamercolor{block line alerted top}{fg=}
+\setbeamercolor{block line alerted middle}{fg=}
+\setbeamercolor{block line alerted bottom}{fg=}
 
 \setbeamercolor{block title example}{parent={block title}, bg=lightgreen}
-\setbeamercolor{block body example}{parent={block body}}
+\setbeamercolor{block body example}{fg=normal text.fg, bg=lightgreen!40}
+\setbeamercolor{block line example top}{fg=}
+\setbeamercolor{block line example middle}{fg=}
+\setbeamercolor{block line example bottom}{fg=}
 
 \if@beamer@colors@set
 
diff --git a/beamercolorthemeut.sty b/beamercolorthemeut.sty
index d5e46d7..b49a10a 100644
--- a/beamercolorthemeut.sty
+++ b/beamercolorthemeut.sty
@@ -50,13 +50,22 @@
 \setbeamercolor{frametitle line}{fg=utgold}
 
 \setbeamercolor{block title}{fg=white, bg=utlightblue}
-\setbeamercolor{block body}{fg=normal text.fg, bg=utblack!10}
+\setbeamercolor{block body}{fg=normal text.fg, bg=utlightblue!15}
+\setbeamercolor{block line top}{fg=}
+\setbeamercolor{block line middle}{fg=}
+\setbeamercolor{block line bottom}{fg=}
 
 \setbeamercolor{block title alerted}{parent={block title}, bg=utred}
-\setbeamercolor{block body alerted}{parent={block body}, fg=utred}
-
-\setbeamercolor{block title example}{parent={block title}, bg=utcyan}
-\setbeamercolor{block body example}{parent={block body}}
+\setbeamercolor{block body alerted}{fg=utred, bg=utred!10}
+\setbeamercolor{block line alerted top}{fg=}
+\setbeamercolor{block line alerted middle}{fg=}
+\setbeamercolor{block line alerted bottom}{fg=}
+
+\setbeamercolor{block title example}{parent={block title}, bg=utgreen}
+\setbeamercolor{block body example}{fg=normal text.fg, bg=utgreen!30}
+\setbeamercolor{block line example top}{fg=}
+\setbeamercolor{block line example middle}{fg=}
+\setbeamercolor{block line example bottom}{fg=}
 
 \addtobeamertemplate{proof begin}{%
   \setbeamercolor{block title}{fg=white, bg=utmagenta}
diff --git a/beamerthemelines.sty b/beamerthemelines.sty
index b11de29..6d1dfe1 100644
--- a/beamerthemelines.sty
+++ b/beamerthemelines.sty
@@ -8,6 +8,7 @@
 \ProvidesPackage{beamerthemelines}[2021/02/28 beamer theme with horizontal lines]
 
 \RequirePackage{tikz}
+\RequirePackage{xstring}
 
 % pass set/noset option to aptero color theme:
 \DeclareOptionBeamer{set}{\PassOptionsToPackage{set}{beamercolorthemeaptero}}
@@ -340,9 +341,124 @@
 \setbeamertemplate{enumerate subitem}[alph] % default, circle, square, ball, alph, arabic, roman
 
 
-%%%%% block environments:
+%%%%% block environment:
+
+\defbeamertemplate{block begin}{lines}[2]{%
+  \par\vskip\medskipamount%
+  \usebeamerfont{block title}%
+  \IfStrEq{\insertblocktitle}{}{}{%
+    \ifbeamercolorempty[fg]{block line top}{}{%
+      \nointerlineskip
+      \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line top}
+        \rule{\columnwidth}{#1}
+      \end{beamercolorbox}
+      \nointerlineskip%
+    }
+    \begin{beamercolorbox}[wd=\columnwidth,ht=2.5ex,dp=1ex,leftskip=2mm,rightskip=2mm]{block title}
+      \strut\insertblocktitle
+    \end{beamercolorbox}}
+  \nointerlineskip
+  \ifbeamercolorempty[fg]{block line middle}{}{%
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#2]{block line middle}
+      \rule{\columnwidth}{#2}
+    \end{beamercolorbox}
+    \nointerlineskip}%
+  \usebeamerfont{block body}%
+  \begin{beamercolorbox}[wd=\columnwidth,colsep=2mm]{block body}
+  }
+
+\defbeamertemplate{block end}{lines}[1][1pt]{%
+  \end{beamercolorbox}%
+  \ifbeamercolorempty[fg]{block line bottom}{}{%
+    \nointerlineskip
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line bottom}
+      \rule{\columnwidth}{#1}
+    \end{beamercolorbox}
+  }%
+}
+
+\setbeamertemplate{block begin}[lines]{1pt}{1pt}
+\setbeamertemplate{block end}[lines][1pt]
+
+
+%%%%% block alerted environment:
+
+\defbeamertemplate{block alerted begin}{lines}[2]{%
+  \par\vskip\medskipamount%
+  \usebeamerfont{block title alerted}%
+  \IfStrEq{\insertblocktitle}{}{}{%
+    \ifbeamercolorempty[fg]{block line alerted top}{}{%
+      \nointerlineskip
+      \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line alerted top}
+        \rule{\columnwidth}{#1}
+      \end{beamercolorbox}
+      \nointerlineskip%
+    }
+    \begin{beamercolorbox}[wd=\columnwidth,ht=2.5ex,dp=1ex,leftskip=2mm,rightskip=2mm]{block title alerted}
+      \strut\insertblocktitle
+    \end{beamercolorbox}}
+  \nointerlineskip
+  \ifbeamercolorempty[fg]{block line alerted middle}{}{%
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#2]{block line alerted middle}
+      \rule{\columnwidth}{#2}
+    \end{beamercolorbox}
+    \nointerlineskip}%
+  \usebeamerfont{block body}%
+  \begin{beamercolorbox}[wd=\columnwidth,colsep=2mm]{block body alerted}
+  }
+
+\defbeamertemplate{block alerted end}{lines}[1][1pt]{%
+  \end{beamercolorbox}%
+  \ifbeamercolorempty[fg]{block line alerted bottom}{}{%
+    \nointerlineskip
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line alerted bottom}
+      \rule{\columnwidth}{#1}
+    \end{beamercolorbox}
+  }%
+}
+
+\setbeamertemplate{block alerted begin}[lines]{1pt}{1pt}
+\setbeamertemplate{block alerted end}[lines][1pt]
+
+
+%%%%% block example environment:
+
+\defbeamertemplate{block example begin}{lines}[2]{%
+  \par\vskip\medskipamount%
+  \usebeamerfont{block title example}%
+  \IfStrEq{\insertblocktitle}{}{}{%
+    \ifbeamercolorempty[fg]{block line example top}{}{%
+      \nointerlineskip
+      \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line example top}
+        \rule{\columnwidth}{#1}
+      \end{beamercolorbox}
+      \nointerlineskip%
+    }
+    \begin{beamercolorbox}[wd=\columnwidth,ht=2.5ex,dp=1ex,leftskip=2mm,rightskip=2mm]{block title example}
+      \strut\insertblocktitle
+    \end{beamercolorbox}}
+  \nointerlineskip
+  \ifbeamercolorempty[fg]{block line example middle}{}{%
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#2]{block line example middle}
+      \rule{\columnwidth}{#2}
+    \end{beamercolorbox}
+    \nointerlineskip}%
+  \usebeamerfont{block body}%
+  \begin{beamercolorbox}[wd=\columnwidth,colsep=2mm]{block body example}
+  }
+
+\defbeamertemplate{block example end}{lines}[1][1pt]{%
+  \end{beamercolorbox}%
+  \ifbeamercolorempty[fg]{block line example bottom}{}{%
+    \nointerlineskip
+    \begin{beamercolorbox}[wd=\columnwidth,hd=#1]{block line example bottom}
+      \rule{\columnwidth}{#1}
+    \end{beamercolorbox}
+  }%
+}
 
-\setbeamertemplate{blocks}[default]
+\setbeamertemplate{block example begin}[lines]{1pt}{1pt}
+\setbeamertemplate{block example end}[lines][1pt]
 
 
 %%%%% title page %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
diff --git a/beamerthemeut.sty b/beamerthemeut.sty
index fe7a967..9c961b8 100644
--- a/beamerthemeut.sty
+++ b/beamerthemeut.sty
@@ -49,9 +49,16 @@
 \setbeamertemplate{enumerate item}[arabic]  % default, circle, square, ball, alph, Alph, arabic, roman, Roman
 \setbeamertemplate{enumerate subitem}[alph] % default, circle, square, ball, alph, arabic, roman
 
-\setbeamertemplate{blocks}[default]          % default, rounded
+\setbeamertemplate{block begin}[lines]{1pt}{1pt} % default, rounded, lines
+\setbeamertemplate{block end}[lines][1pt]
 
-\setbeamertemplate{title page}[leftlines]    % leftlines, centerlines
+\setbeamertemplate{block alerted begin}[lines]{1pt}{1pt} % default, rounded, lines
+\setbeamertemplate{block alerted end}[lines][1pt]
+
+\setbeamertemplate{block example begin}[lines]{1pt}{1pt} % default, rounded, lines
+\setbeamertemplate{block example end}[lines][1pt]
+
+\setbeamertemplate{title page}[leftlines]          % leftlines, centerlines
 \setbeamertemplate{title page graphic line}[default][1.4ex]
 \setbeamertemplate{title page title line}[default][0.75pt]
 \setbeamertemplate{title page author and}[line]    % space, comma, line, and
diff --git a/lines-example.tex b/lines-example.tex
index 273f512..b2c26de 100644
--- a/lines-example.tex
+++ b/lines-example.tex
@@ -8,6 +8,8 @@
 \institute[T\"ubingen]{Neuroethology, University of T\"ubingen}
 \date[2021]{March 2021}
 
+\setbeamerfont{block body}{size=\small}
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{document}
@@ -101,7 +103,7 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
 \begin{frame}[fragile]{Itemize and enumerate}
   \begin{minipage}[t]{0.45\textwidth}
-    \vspace{-2ex}
+    \vspace{-3ex}
     \begin{block}{Itemize with overlays}
       \verb!\begin{itemize}!\\
         \verb!\item Apple!\\
@@ -119,7 +121,7 @@
   \end{minipage}
   \hfill
   \begin{minipage}[t]{0.45\textwidth}
-    \vspace{-2ex}
+    \vspace{-3ex}
     \begin{block}{Enumerate with overlays}
       \verb!\begin{enumerate}!\\
         \verb!\item<2-> Apple!\\
@@ -178,8 +180,8 @@
 
 \begin{frame}[fragile]{Nested itemize and enumerate}
   \begin{minipage}[t]{0.45\textwidth}
-    \vspace{-2ex}
-    \begin{block}{Itemize}\small
+    \vspace{-3ex}
+    \begin{block}{Itemize}
       \verb!\begin{itemize}!\\
       \verb!\item Apple!\\
       \verb!  \begin{itemize}!\\
@@ -200,8 +202,8 @@
   \end{minipage}
   \hfill
   \begin{minipage}[t]{0.45\textwidth}
-    \vspace{-2ex}
-    \begin{block}{Enumerate}\small
+    \vspace{-3ex}
+    \begin{block}{Enumerate}
       \verb!\begin{enumerate}!\\
       \verb!\item Apple!\\
       \verb!  \begin{enumerate}!\\
@@ -235,22 +237,35 @@
   \end{block}
 \end{frame}
 
-\begin{frame}{Blocks and theorems}
+\begin{frame}{Block environments}
   \begin{block}{Some block}
     Block with title and content: \texttt{block} environment with title as argument.
   \end{block}
+  \begin{block}{}
+    Block without title.
+  \end{block}
   \begin{alertblock}{Careful!}
     Alert block with title and content: \texttt{alertblock} environment with title as argument.
   \end{alertblock}
-  \begin{example}
-    Example block with content: \texttt{example} environment.
-  \end{example}
-  \begin{definition}
-    Definition block with content: \texttt{definition} environment.
-  \end{definition}
-  \begin{proof}
-    Proof block with content: \texttt{proof} environment.
-  \end{proof}
+  \begin{alertblock}{}
+    Alert block without title.
+  \end{alertblock}
+  \begin{exampleblock}{Example}
+    Example block with title and content: \texttt{exampleblock} environment.
+  \end{exampleblock}
+  \begin{exampleblock}{}
+    Example block without title.
+  \end{exampleblock}
+\end{frame}
+
+\begin{frame}{Theorems}
+  Not supported yet.
+  % \begin{definition}
+  %   Definition block with content: \texttt{definition} environment.
+  % \end{definition}
+  % \begin{proof}
+  %   Proof block with content: \texttt{proof} environment.
+  % \end{proof}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
@@ -324,9 +339,6 @@
   \begin{block}{Just space}
     \verb!\setbeamertemplate{footline separator}[space]!
   \end{block}
-  \begin{block}{Color}
-    \verb!\setbeamercolor{footline separator}{fg=black}!
-  \end{block}
 \end{frame}
 
 \begin{frame}[fragile]{Footline page}
diff --git a/ut-example.tex b/ut-example.tex
index dc501e1..0107443 100644
--- a/ut-example.tex
+++ b/ut-example.tex
@@ -9,6 +9,8 @@
 \titlelogo{\includegraphics[height=6ex]{UT_MNF_RGB}}
 \titlegraphic{\includegraphics[width=\textwidth]{efishtitle}}
 
+\setbeamerfont{block body}{size=\small}
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \begin{document}
@@ -22,6 +24,7 @@
       \verb!\documentclass[aspectratio=169,t]{beamer}!\\
       \verb!\usetheme[author,date,title,page]{ut}!
   \end{block}
+  \vspace{2ex}
   Options select content of footline (defaults to \verb![author,page,logo]!):
   \begin{itemize}
   \item \verb!author! / \verb!hideauthor!
@@ -99,7 +102,7 @@
 \begin{frame}[fragile]{Nested itemize and enumerate}
   \begin{minipage}[t]{0.45\textwidth}
     \vspace{-2ex}
-    \begin{block}{Itemize}\small
+    \begin{block}{Itemize}
       \verb!\begin{itemize}!\\
       \verb!\item Apple!\\
       \verb!  \begin{itemize}!\\
@@ -121,7 +124,7 @@
   \hfill
   \begin{minipage}[t]{0.45\textwidth}
     \vspace{-2ex}
-    \begin{block}{Enumerate}\small
+    \begin{block}{Enumerate}
       \verb!\begin{enumerate}!\\
       \verb!\item Apple!\\
       \verb!  \begin{enumerate}!\\
@@ -150,26 +153,41 @@
   Structural \structure{emphasis} is provided by the \verb!\structure{}! command.
 \end{frame}
 
-\begin{frame}{Blocks}
-  Carefully used, they bring color into the slide.
+\begin{frame}{Block environments with title}
   \begin{block}{Some block}
-    Block with title and content: \texttt{block} environment with title as argument.
+    \texttt{block} environment with title as argument.
   \end{block}
   \begin{alertblock}{Careful!}
-    Alert block with title and content: \texttt{alertblock} environment with title as argument.
+    \texttt{alertblock} environment with title as argument.
+  \end{alertblock}
+  \begin{exampleblock}{Example}
+    \texttt{exampleblock} environment with title as argument.
+  \end{exampleblock}
+\end{frame}
+
+\begin{frame}{Block environments without title}
+  \begin{block}{}
+    Block with empty title.\\
+    And just some text.
+  \end{block}
+  \begin{alertblock}{}
+    Alert block with empty title.\\
+    And just some text.
   \end{alertblock}
-  \begin{example}
-    Example block with content: \texttt{example} environment.
-  \end{example}
+  \begin{exampleblock}{}
+    Example block with empty title.\\
+    And just some text.
+  \end{exampleblock}
 \end{frame}
 
 \begin{frame}{Theorems}
-  \begin{definition}
-    Definition block with content: \texttt{definition} environment.
-  \end{definition}
-  \begin{proof}
-    Proof block with content: \texttt{proof} environment.
-  \end{proof}
+  Not supported yet.
+  % \begin{definition}
+  %   Definition block with content: \texttt{definition} environment.
+  % \end{definition}
+  % \begin{proof}
+  %   Proof block with content: \texttt{proof} environment.
+  % \end{proof}
 \end{frame}
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%