Best Reply
\begin{tikzpicture}[scale=0.7]
\tiny
\draw (0,0) -- (6,0) node [below] {$s_B$};
\draw (0,0) -- (0,6) node [left] {$s_A$};
\node [below] at (0,0) {$O$};
\draw(0,0.7) to [out=15,in=230] (5.5,4);
\node [below] at (5.4,3.3) {$R_A(s_B)$};
\draw [->] (3,0.5) -- (3,1.4);
\draw [xshift=7cm](0,0) -- (6,0) node [below] {$s_B$};
\draw [xshift=7cm] (0,0) -- (0,6) node [left] {$s_A$};
\node [xshift=4.7cm][below] at (0,0) {$O$};
\draw [xshift=7cm] (1,0) to [out=40,in=260] (3.5,3);
\draw [xshift=7cm] (3.5,3) to [out=85,in=220] (5.5,5);
\node [xshift=6cm][below] at (4.6,4.4) {$R_B(s_A)$};
\draw [xshift=7cm][->] (0.5,2.5) -- (2,2.5);
\end{tikzpicture}
Nash Equilibrium
\begin{tikzpicture}[scale=0.7]
\tiny
\draw (0,0) -- (6,0) node [below] {$s_B$};
\draw (0,0) -- (0,6) node [left] {$s_A$};
\node [below] at (0,0) {$O$};
\draw (0,0.7) to [out=15,in=230] (5.5,4.6);
\node [below] at (6,4) {$R_A(s_B)$};
\node [below] at (4,5) {$R_B(s_A)$};
\draw (1,0) to [out=40,in=260] (3.5,3);
\draw (3.5,3) to [out=85,in=220] (5.3,5.3);
\node [below] at (3.3,0) {$s^*_B$};
\draw[dotted](3.3,0)--(3.3,2.4);
\draw[dotted](0,2.4)--(3.3,2.4);
\node [left] at (0,2.4) {$s^*_A$};
\end{tikzpicture}
Mixed-strategy Nash equilibrium
\begin{tikzpicture}[scale=0.8]
\tiny
% Left Graph
\draw (0,0) -- (3.3,0);
\draw (0,0) -- (0,3.3);
\draw [thick] (0,0)--(1.5,0)--(1.5,3) -- (3,3);
\draw [dashed] (0,3)--(1.5,3);
\draw [dashed] (3,3)--(3,0);
\node [right] at (3,3) {$R_A(q_B)$};
\node [below] at (0,0) {$0$};
\node [below] at (1.5,0) {$1\over 2$};
\node [below] at (3,0) {$1$};
\node [right] at (3.3,0) {$q_B$};
\node [left] at (0,3) {$1$};
\node [above] at (0,3.3) {$q_A$};
% Middle Graph
\draw [xshift=5.1cm] (0,0) -- (3.3,0);
\draw [xshift=5.1cm] (0,0) -- (0,3.3);
\draw [xshift=5.1cm,thick] (3,0) -- (3,1.5)--(0,1.5)--(0,3);
\draw [xshift=5.1cm][dashed] (0,3)--(3,3);
\draw [xshift=5.1cm][dashed] (0,1.5)--(3,1.5);
\draw [xshift=5.1cm][dashed] (3,3)--(3,1.5);
\node [xshift=3.9cm][right] at (3.3,0.4) {$R_B(q_A)$};
\node [xshift=4.1cm][below] at (0,0) {$0$};
\node [xshift=4.1cm][left] at (0,1.5) {$1\over 2$};
\node [xshift=4.1cm][below] at (3,0) {$1$};
\node [xshift=4.1cm][right] at (3.3,0) {$q_B$};
\node [xshift=4.1cm][left] at (0,3) {$1$};
\node [xshift=4.1cm][above] at (0,3.3) {$q_A$};
% Right Graph
\draw [xshift=10cm] (0,0) -- (3.3,0);
\draw [xshift=10cm] (0,0) -- (0,3.3);
\draw [xshift=10cm] (3,0) -- (3,1.5);
\draw [xshift=10cm,thick] (0,0)--(1.5,0)--(1.5,3) -- (3,3);
\draw [xshift=10cm,thick] (3,0) -- (3,1.5)--(0,1.5)--(0,3);
\draw [xshift=10cm][dashed] (0,3)--(3,3);
\draw [xshift=10cm][dashed] (0,1.5)--(3,1.5);
\draw [xshift=10cm][dashed] (3,3)--(3,1.5);
\node [xshift=8cm][right] at (3,3) {$R_A(q_B)$};
\node [xshift=8cm][right] at (3,1) {$R_B(q_A)$};
\node [xshift=8cm][below] at (0,0) {$0$};
\node [xshift=8cm][left] at (0.1,1.5) {$q^*_A=\frac{1}{2}$};
\node [xshift=8cm][below] at (3,0) {$1$};
\node [xshift=8cm][right] at (3.3,0) {$q_B$};
\node [xshift=8cm][left] at (0,3) {$1$};
\node [xshift=8cm][above] at (0,3.3) {$q_A$};
\draw [xshift=10cm] (1.5,0) -- (1.5,3);
\draw [xshift=10cm] (1.5,3) -- (3,3);
\node [xshift=8cm][below] at (1.5,0) {$q^*_B=\frac{1}{2}$};
\end{tikzpicture}