\documentclass[tikz,border=10pt]{standalone}
                        \IfFileExists{newpxtext.sty}{\usepackage{newpxtext,newpxmath}}{}
                        \linespread{1.10}
                        \usetikzlibrary{shapes}
                        \usetikzlibrary{arrows.meta}
                        \usepackage{graphicx}

                        \begin{document}

                        % TikZ code with built-in styling for game trees
% TikZ libraries required for game trees
\usetikzlibrary{shapes}
\usetikzlibrary{arrows.meta}

% Style settings for game tree formatting
\tikzset{
    every node/.append style={font=\sffamily\itshape},
    every text node part/.append style={align=center},
    node distance=1.5mm,
    thick
}

% Built-in macro definitions for game tree drawing
\newdimen\ndiam
\ndiam1.5mm
\newdimen\sqwidth
\sqwidth1.6mm
\newdimen\spx
\spx.7mm
\newdimen\spy
\spy.5mm
\newdimen\paydown
\paydown2.5ex
\newdimen\treethickn
\treethickn1.0pt
\definecolor{chancecolor}{RGB}{117,145,56}
\definecolor{playeronecolor}{RGB}{234,51,35}
\colorlet{playertwocolor}{blue}
\colorlet{playerthreecolor}{orange}
\colorlet{playerfourcolor}{purple}
\colorlet{playerfivecolor}{cyan}
\colorlet{playersixcolor}{magenta}

% Game tree content from /home/docs/checkouts/readthedocs.org/user_builds/gambitproject/checkouts/936/catalog/img/books/bonanno18/fig3_10.ef
\begin{tikzpicture}[scale=0.8
  , StealthFill/.tip={Stealth[line width=.7pt,inset=0pt,length=13pt,angle'=30]}]
% \draw [help lines, color=green] (-5,0) grid (5,-6);
%% player 1 name Entrant
\def\playerone{Entrant}
%% player 2 name Incumbent
\def\playertwo{Incumbent}
%% level -2.0 node 1 player 1
\draw [line width=\treethickn] (0,2)
   ;
%% level 2.0 node 1 player 2 xshift -2.4000000000000004 from -2.0,1 move Enter
\draw [line width=\treethickn,color=playeronecolor] (-2.4,-2)
   -- (0,2);
\draw (-1.2,0) node[left,xshift=-0.5mm,color=playeronecolor] {Enter\strut};
%% level 6.0 node 1 xshift -1.6 from 2.0,1 move Fight payoffs 0 0
\draw [line width=\treethickn,color=playertwocolor] (-4,-6)
   node[below,yshift=0.1\paydown,color=playeronecolor] {$\mathsf{0}\strut$}
   node[below,yshift=-0.9\paydown,color=playertwocolor] {$\mathsf{0}\strut$}
   -- (-2.4,-2);
\draw (-3.2,-4) node[left,xshift=-0.5mm,color=playertwocolor] {Fight\strut};
%% level 6.0 node 2 xshift 1.6 from 2.0,1 move Accommodate payoffs 2 2
\draw [line width=\treethickn,color=playertwocolor] (-0.8,-6)
   node[below,yshift=0.1\paydown,color=playeronecolor] {$\mathsf{2}\strut$}
   node[below,yshift=-0.9\paydown,color=playertwocolor] {$\mathsf{2}\strut$}
   -- (-2.4,-2);
\draw (-1.6,-4) node[right,xshift=0.5mm,color=playertwocolor] {Accommodate\strut};
%% level 6.0 node 3 xshift 2.4000000000000004 from -2.0,1 move Stay~out payoffs 1 5
\draw [line width=\treethickn,color=playeronecolor] (2.4,-6)
   node[below,yshift=0.1\paydown,color=playeronecolor] {$\mathsf{1}\strut$}
   node[below,yshift=-0.9\paydown,color=playertwocolor] {$\mathsf{5}\strut$}
   -- (0,2);
\draw (1.2,-2) node[right,xshift=0.5mm,color=playeronecolor] {Stay~out\strut};
\node[inner sep=0pt,minimum size=\ndiam,draw=playeronecolor,fill=playeronecolor,shape=circle] at (0,2) {};
\node[inner sep=0pt,minimum size=\ndiam,draw=playertwocolor,fill=playertwocolor,shape=circle] at (-2.4,-2) {};

% Player color legend
\begin{scope}[scale=1,shift={(-5.5,2.0)}]
\node[inner sep=0pt,minimum size=\ndiam,draw=playeronecolor,fill=playeronecolor,shape=circle] at (0,0) {};
\node[anchor=west] at (0.3,0) {Entrant};
\node[inner sep=0pt,minimum size=\ndiam,draw=playertwocolor,fill=playertwocolor,shape=circle] at (0,-0.625) {};
\node[anchor=west] at (0.3,-0.625) {Incumbent};
\end{scope}

\end{tikzpicture}

                        \end{document}