diff --git a/slides/sections/0.md b/slides/sections/0.md
index ed8672c..f92120e 100644
--- a/slides/sections/0.md
+++ b/slides/sections/0.md
@@ -84,6 +84,7 @@ header-includes: |
     \vspace{\baselineskip}
   }
 
+  % don't hide animation completely
   \setbeamercovered{transparent}
 
   % strike macro
@@ -102,6 +103,10 @@ header-includes: |
   \usepackage{multirow}
   \usepackage{booktabs}
 
+  %% tikz setup
+  \usepackage{tikz}
+  \usetikzlibrary{arrows.meta}
+
   %% math macros
 
   % thus
diff --git a/slides/sections/4.md b/slides/sections/4.md
index 581f79b..ee7c95a 100644
--- a/slides/sections/4.md
+++ b/slides/sections/4.md
@@ -92,7 +92,7 @@ Half Sample Mode[@robertson74]
 \setbeamercovered{}
 
 \begin{center}
-\begin{tikzpicture}[remember picture]
+\begin{tikzpicture}[remember picture, >=Stealth]
   % line
   \draw [line width=3, ->, cyclamen] (-5,0) -- (5,0);
   \node [right] at (5,0) {$x$};
diff --git a/slides/sections/5.md b/slides/sections/5.md
index c1e232a..cd8311a 100644
--- a/slides/sections/5.md
+++ b/slides/sections/5.md
@@ -25,7 +25,7 @@ Quantify distance between expected and observed CDF. KS statistic:
 :::  {.column width=50%}
   \setbeamercovered{}
   \begin{center}
-  \begin{tikzpicture}
+  \begin{tikzpicture}[>=Stealth]
     % empiric
     \draw [cyclamen, fill=cyclamen!20!white] (-2.5,0) rectangle (-1.5,0.5);
     \draw [cyclamen, fill=cyclamen!20!white] (-1.5,0) rectangle (-0.9,1);
diff --git a/slides/sections/6.md b/slides/sections/6.md
index 49a9b28..f50b8d1 100644
--- a/slides/sections/6.md
+++ b/slides/sections/6.md
@@ -108,7 +108,7 @@ $$
 . . .
 
 \begin{center}
-\begin{tikzpicture}
+\begin{tikzpicture}[>=Stealth]
   % line
   \draw [line width=3, ->, cyclamen] (0,0) -- (10,0);
   \node [right] at (10,0) {$u$};
diff --git a/slides/sections/8.md b/slides/sections/8.md
index 900f4a1..bc0c07b 100644
--- a/slides/sections/8.md
+++ b/slides/sections/8.md
@@ -25,7 +25,7 @@ $$
 
 \setbeamercovered{}
 \begin{center}
-\begin{tikzpicture}
+\begin{tikzpicture}[>=Stealth]
   %notes
   \draw [very thick, gray] (0,0) -- (0,3);
   \draw [very thick, gray] (-1.45,1.5) -- (1.45,1.5);