\begin{figure*}[t!]
\centering
% \begin{subfigure}{0.30\textwidth}
% \subfigure[DoorKey 8$\times$8 C5]{
% \centering
% \includegraphics[width=.30\linewidth]{figure/source/experiments/MiniGrid-Color-DoorKey-Random-Goal-8x8-C5-v0.pdf}
% \label{fig:experiments_doorkey_c2}
% }\hfill
% \vspace{-3mm}
% \caption{DoorKey 8$\times$8 C5}
% \end{subfigure}
% \begin{subfigure}{0.30\textwidth}
\subfigure[DoorKey-Easy]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/MiniGrid-Color-DoorKey-Random-Goal-12x12-C2-v0.pdf}
\label{fig:experiments_doorkey_c2}
}%\hfil
% \vspace{-3mm}
% \caption{DoorKey 12$\times$12 C3}
% \end{subfigure}
% \begin{subfigure}{0.30\textwidth}
\subfigure[DoorKey-Normal]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/MiniGrid-Color-DoorKey-Random-Goal-12x12-C3-v0.pdf}
\label{fig:experiments_doorkey_c3}
}%\hfil
\subfigure[DoorKey-Hard]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/MiniGrid-Color-DoorKey-Random-Goal-12x12-C4-v0.pdf}
\label{fig:experiments_doorkey_c4}
}
\vskip\baselineskip
\vspace{-10pt}
\centering
% \caption{DoorKey 12$\times$12 C5}
% \end{subfigure} \\
% %
% \begin{subfigure}{0.30\textwidth}
\subfigure[Sokoban-Easy]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/Sokoban-PushAndPull-7x7-B1-C2.pdf}
\label{fig:experiments_sokoban_c2}
}%\hfil
% \caption{Sokoban 7$\times$7 C2}
% \end{subfigure}
% \begin{subfigure}{0.30\textwidth}
\subfigure[Sokoban-Normal]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/Sokoban-PushAndPull-7x7-B1-C3.pdf}
\label{fig:experiments_sokoban_c3}
}%\hfil
% \caption{Sokoban 7$\times$7 C3}
% \end{subfigure}
% \begin{subfigure}{0.30\textwidth}
\subfigure[Sokoban-Hard]{
\centering
\includegraphics[width=.30\linewidth]{figure/source/experiments/Sokoban-PushAndPull-7x7-B1-C4.pdf}
\label{fig:experiments_sokoban_c4}
}
% \caption{Sokoban 7$\times$7 C4}
% \end{subfigure}
% \vspace{-5pt}
\caption{Learning curves. The average episodic return is depicted by lines, and the shaded areas represent the $95\%$ confidence intervals.
}
% \vspace{-10pt}
\label{fig:experiments}
\end{figure*}
