diff --git a/default.nix b/default.nix
index 0b47584..dc26d1f 100644
--- a/default.nix
+++ b/default.nix
@@ -9,6 +9,8 @@
 , pugixml
 , qtbase
 , wrapQtAppsHook
+, fetchzip
+, runCommand
 , withPortabilityTweaks ? false
 }:
 
@@ -41,7 +43,47 @@ stdenv.mkDerivation {
     git
     wrapQtAppsHook
     (texlive.combine {
-      inherit (texlive) scheme-small standalone pgfplots;
+      inherit (texlive) scheme-small standalone pgfplots unicode-math;
+      # https://ctan.org/tex-archive/fonts/lete-sans-math
+      # TODO use buildTeXLivePackage
+#      lete-sans-math = pkgs.texlivePackages.buildTeXLivePackage {
+##        revision = 64540;
+#        shortdesc = "Lato-based OpenType Math font for LuaTeX and XeTeX";
+##        stripPrefix = 0;
+##        fontMaps = [
+##          "Map andika.map"
+##        ];
+##        sha512.run = "4da9904459345033aa87deeb0019c8c4a39fbafcd59d973717ed2c4a410ece528944c69669b6a5ecf6ef8bb790f60bba909468e001485c405e7cf8775b7533e5";
+##        sha512.doc = "50684857dc25ad942aff18eedec04c9e27e4e408f748c208f8527c5096e600d26769ec6f82e2f02e72ab472dfb662f12bb009156293a12daa2dc0676d63ed446";
+#        hasRunfiles = false;
+#        license = [ "lppl13c" ];
+#        version = "0.41";
+#      };
+      lete-sans-math = {
+        pkgs = [
+          (runCommand "lete-sans-math" {
+            src = fetchzip {
+              url = "https://mirrors.ctan.org/fonts/lete-sans-math.zip";
+#              url = "https://raw.githubusercontent.com/abccsss/LeteSansMath/refs/tags/v0.41/lete-sans-math.sty";
+  #            url = "https://raw.githubusercontent.com/PierreSenellart/apxproof/1ac14c47b8351b693ca05eec73dca1332a517ac9/apxproof.sty";
+  #            sha256 = "sha256-XSgtXsOwhMu2Wo4hVp8ZfaPWgjEEg3EBn5/BhD3xkMA=";
+#              hash = "sha256-aUKS2tCbC+eBFPMSJuzzkWgFkSqWnizekTOnoK2f5L4=";
+              hash = "sha256-pz5qKo4ALYuTjGeO9YqxB6hcrqIkT4S8U28cLMZdG5U=";
+            };
+            passthru = {
+              pname = "lete-sans-math";
+              version = "0.45";
+              tlType = "run";
+            };
+          } ''
+            mkdir -p \
+              $out/tex/latex/lete-sans-math/ \
+              $out/fonts/opentype/public/lete-sans-math/
+            cp $src/*.sty $src/*.ltx $out/tex/latex/lete-sans-math/
+            cp $src/*.otf $out/fonts/opentype/public/lete-sans-math/
+          '')
+        ];
+      };
     })
   ];
 
diff --git a/doc/CMakeLists.txt b/doc/CMakeLists.txt
index 749062d..d49279a 100644
--- a/doc/CMakeLists.txt
+++ b/doc/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_custom_target( doc )
+add_subdirectory( "${CMAKE_CURRENT_SOURCE_DIR}/latex" )
 
 configure_file(
 	"${CMAKE_CURRENT_SOURCE_DIR}/openemsh.1.in"
diff --git a/doc/latex/CMakeLists.txt b/doc/latex/CMakeLists.txt
new file mode 100644
index 0000000..90689ea
--- /dev/null
+++ b/doc/latex/CMakeLists.txt
@@ -0,0 +1,13 @@
+if( CMakeUtils_Latex_FOUND )
+	compile_latex_file( "interval" REGISTER_TO "LATEX_FILES" VERBOSE )
+
+	add_custom_target( "latex" DEPENDS ${LATEX_FILES} )
+	add_dependencies( "doc" "latex" )
+
+	install(
+		FILES
+			${LATEX_FILES}
+		DESTINATION "${CMAKE_INSTALL_DOCDIR}/openemsh"
+		OPTIONAL
+		)
+endif()
diff --git a/doc/latex/interval.tex b/doc/latex/interval.tex
new file mode 100644
index 0000000..e283867
--- /dev/null
+++ b/doc/latex/interval.tex
@@ -0,0 +1,235 @@
+\documentclass[tikz]{standalone}
+
+%\usepackage{etoolbox}
+\usepackage{fontspec}
+\setmainfont[Ligatures=TeX, Mapping=tex-text]{Lato}
+%\usepackage[default]{lato}
+\usepackage{unicode-math}
+%\setmathfont{Lete Sans Math}
+\setmathfont{LeteSansMath.otf}
+%\usepackage{lete-sans-math}
+\usepackage{tikz}
+\usetikzlibrary{math}
+\usepackage{xfp}
+
+\begin{document}
+\begin{tikzpicture}
+
+\def\width{10}
+\def\height{5}
+\def\ox{\fpeval{\width /2}}
+\def\oy{\fpeval{\height /2}}
+\coordinate (O) at (\ox,\oy);
+
+\tiny
+\path [use as bounding box] (0,0) rectangle (\width,\height);
+
+% SHAPE
+%\filldraw [line width=0.5pt, fill=orange] (\ox,\oy)
+%	+(-0.5,-0.5) node[draw, fill=black, circle, inner sep=1pt] {} node[below left] {0} --
+%	+(0.5,-0.5) node[draw, fill=black, circle, inner sep=1pt] {} node[below right] {1} --
+%	+(0.5,0.5) node[draw, fill=black, circle, inner sep=1pt] {} node[above right] {2} --
+%	+(-0.5,0.5) node[draw, fill=black, circle, inner sep=1pt] {} node[above left] {3} --
+%	cycle;
+
+% PORTS
+%\draw [line width=2pt] (\ox,\oy) ++(-0.5,0) node[right] {1} +(0,-0.5) -- +(0,0.5);
+%\draw [line width=2pt] (\ox,\oy) ++(0,-0.5) node[above] {2} +(-0.5,0) -- +(0.5,0);
+
+
+
+% MID LINE
+\draw [line width=0.5pt, dotted] (O) +(0,-2) node[below] {$m$} -- +(0,1);
+
+% EDGE LINES
+\draw [line width=0.5pt, dotted] (\ox,\oy) +(-4,-2) node[below] {$x$} -- +(-4,1);
+\draw [line width=0.5pt, dotted] (\ox,\oy) +(4,-2) node[below] {$x$} -- +(4,1);
+
+% POLICY LINES
+%\draw [line width=0.5pt, orange] (\ox,\oy) ++(-4,0)
+%	+(-0.2,-1) -- +(-0.2,1)
+%	+(0.2,-1) -- +(0.2,1);
+%\draw [line width=0.5pt, orange] (\ox,\oy) ++(4,0)
+%	+(-0.1,-1) -- +(-0.1,1)
+%	+(0.2,-1) -- +(0.2,1);
+% Function: policy line
+% #1 : x
+% #2 : x1 (relative to x)
+% #3 : x2 (relative to x)
+\newcommand{\policylines}[3]{%
+	\draw [line width=0.5pt, orange] (\ox,\oy) ++(#1,0)
+		+(#2,-1) -- +(#2,1)
+		+(#3,-1) -- +(#3,1)%
+}
+\policylines{-4}{-0.3}{0.3}; % 1/2 - Halfs rule
+\policylines{4}{-0.1}{0.2}; % 1/3 - Thirds rule
+
+% LINES
+%\newcommand{\drawline}[2][violet]{%
+%	\draw [line width=0.5pt, color={#1}] (\ox,\oy)
+%		+(#2,-1) -- +(#2,1)%
+%}
+%\drawline[orange]{3};
+%\newcommand{\drawline}[2][violet]{%
+%	\draw [line width=0.5pt, {#1}] (\ox,\oy)
+\newcommand{\drawline}[2][line width=0.5pt, color=black]{%
+	\draw [{#1}] (\ox,\oy)
+		+(#2,-1) -- +(#2,1)%
+}
+%\drawline[orange, dotted]{3};
+%\drawline{2.5};
+%
+%\draw [line width=0.5pt, violet] (\ox,\oy) ++(-3.7,-1)
+%%	++(0,0) +(0,2)
+%	++(1.2,0) -- +(0,2)
+%	++(2.4,0) -- +(0,2)
+%;
+
+
+% First, produce a list of lines coordinates
+% Then, use the list to draw the lines and draw annotations
+% https://tex.stackexchange.com/questions/662928/is-this-the-right-way-to-understand-let-def-edef-gdef-xdef-newcommand-ren
+% edef daclare a var, performing expansion
+% xdef declare a global edef var
+\xdef\lines{}
+% TODO define as func with args { x, d_init, d, direction }
+\foreach \n in {1,...,2} {
+	\edef\tmp{\lines,\n}
+	\xdef\lines{\tmp}
+}
+
+%%%% #1 : output var
+%%%% #2 : n
+%%%% #3 : x
+%%%% #4 : d
+%%%% #5 : d_init
+%%%% #6 : lambda
+%%%% #7 : direction
+%%%\newcommand{\createlines}[6] {%
+%%%	% ##1 : n
+%%%	\newcommand{\calculate}[1] {%
+%%%%		\fpeval{#3 + ##1}%
+%%%		\fpeval{(#3 + #5) + (#4 * (#6 ^ ##1))}%
+%%%	}
+%%%	% ##1 : s
+%%%	% ##2 : d
+%%%	%% ##3 : n
+%%%	\newcommand{\calculates}[2] {%
+%%%%		\fpeval{#3 + ##1}%
+%%%		\fpeval{##1 + (##2 * #6)}%
+%%%	}
+%%%	\edef\currents{\fpeval{#3 + #5}}
+%%%	\edef\currentd{#4}
+%%%	\expandafter\xdef\csname #1\endcsname{}
+%%%
+%%%	\foreach \n in {1,...,#2} {%
+%%%		\edef\currentd{\fpeval{\currentd * #6}}
+%%%		\edef\currents{\fpeval{\currents + \currentd}}
+%%%		\ifnum \n = 1%
+%%%%			\edef\tooutput{\calculate{\n}}%
+%%%			\edef\tooutput{\currents}%
+%%%%			\edef\tooutput{\calculates{\currents}{\currentd}}%
+%%%		\else%
+%%%%			\edef\tooutput{\csname #1\endcsname,\calculate{\n}}%
+%%%			\edef\tooutput{\csname #1\endcsname,\currents}%
+%%%%			\edef\tooutput{\csname #1\endcsname,\calculate{\n}}%
+%%%		\fi%
+%%%		\expandafter\xdef\csname #1\endcsname{\tooutput}%
+%%%	}%
+%%%}
+
+% #1 : output var
+% #2 : n
+% #3 : x
+% #4 : d
+% #5 : d_init
+% #6 : lambda
+% #7 : direction (+ | -)
+\newcommand{\createlines}[7] {%
+	\tikzmath{
+		real \d, \s;
+		\d = #4;
+		\s = #3 #7 #5;
+		let \ret =;
+		for \i in {1,...,#2} {
+			\d = \d * #6;
+			\s = \s #7 \d;
+			if \i == 1
+			then { \ret = \s; }
+			else { \ret = "\ret,\s"; };
+		};
+	}
+	\expandafter\xdef\csname #1\endcsname{\ret}
+}
+
+%\createlines{linus}{3}{-4}
+%\createlines{linus}{3}{-4}{0.6}{0.3}{2}
+\createlines{lines}{7}{-4}{0.6}{0.3}{1.1}{+}
+
+\edef\orig{\fpeval{-4+0.3}}
+
+\foreach \n [expand list=true, count=\i] in {\lines} {
+	\drawline[green]{\n};
+%	\draw [line width=0.5pt, red] (\ox,\oy)
+%		++(\n,-1) -- +(0,2) node[above] {\n};
+
+%	\draw [line width=0.5pt] (\ox,\oy) ++(-4,0) ++(0.3,0)
+	\draw [line width=0.5pt] (\ox,\oy) ++(\orig,0)
+		++(0,1) -- +(0,0.5);
+	\ifnum \i = 4
+		\draw [line width=0.5pt] (\ox,\oy)
+			++(\n,1) -- +(0,0.5);
+		\draw [line width=0.5pt] (\ox,\oy) ++(0,1.5)
+			+(\orig,0)
+			.. controls +(0,0.3) and +(0,0.3) ..
+			+(\n,0)
+			+(\fpeval{(\orig+\n)/2},0.2) node[above] {$z$}
+			+(\fpeval{(\orig+\n)/2},0.4) node[above] {$lz=\i$};
+	\fi
+}
+
+\edef\dmax{1}
+
+\foreach \n [
+	expand list=true,
+	count=\i,
+	remember=\n as \lastn (initially \fpeval{-4+0.3})
+] in {\lines} {
+	\draw [line width=0.5pt] (\ox,\oy) ++(0,1)
+		+(\lastn,0) .. controls +(0,0.2) and +(0,0.2) .. +(\n,0)
+		+(\fpeval{(\lastn+\n)/2},0.2) node[above] {$d\cdot\lambda$$^\i$};
+
+	\pgfmathparse{\dmax < \fpeval{abs(\lastn-\n)}}
+	\ifnum \pgfmathresult>0
+		\draw [line width=0.5pt] (\ox,\oy) ++(0,1)
+			++(\lastn,0) .. controls +(0,-0.2) and +(0,-0.2) .. +(\dmax,0)
+			+(\fpeval{(\dmax)/2},-0.2) node[below] {$d_{max}$};
+	\fi
+}
+
+
+
+% ANNOTATIONS
+\draw [line width=0.5pt] (\ox,\oy) ++(-4,1)
+	+(-0.3,0) .. controls +(0,0.2) and +(0,0.2) .. +(0.3,0)
+	+(0,0.2) node[above] {$d$};
+
+\draw [line width=0.5pt] (\ox,\oy) ++(-4,-1)
+	+(0,0) .. controls +(0,-0.1) and +(0,-0.1) .. +(0.3,0)
+	+(0.25,-0.1) node[below] {$d_{init}$};
+
+\draw [line width=0.5pt] (\ox,\oy) ++(0,-1)
+	+(-3.7,0) .. controls +(0,-0.2) and +(0,-0.2) .. +(0,0)
+	+(-2,-0.2) node[below] {$s$};
+
+%\draw [line width=0.5pt, yellow] (\ox,\oy) ++(0,-1)
+%	+(-3.7,0) to [bend right=30] +(0,0)
+%	+(-2,-0.2) node[below] {s};
+
+\draw [line width=0.5pt] (\ox,\oy) ++(0,-1.5)
+	+(-4,0) .. controls +(0,-0.2) and +(0,-0.2) .. +(0,0)
+	+(-2,-0.2) node[below] {$h$};
+
+
+\end{tikzpicture}
+\end{document}