\begin{figure}
  \begin{tikzpicture}[>=latex]

  \shade[top color=i6colorscheme3,bottom color=i6colorscheme4,rounded corners]
    (-25,-7.5)    rectangle (13,41);
  \shade[top color=i6colorscheme2,bottom color=i6colorscheme3,rounded corners]
    (-23,6.5)     rectangle (12,40);
  \shade[top color=white,bottom color=i6colorscheme2,rounded corners]
    (-21,22.5)    rectangle (11,39);

  \node [rotate=90] at (-20,31) {\large \bf Level 0};
  \node [rotate=90] at (-22,31) {\large \bf Level 1};
  \node [rotate=90] at (-24,31) {\large \bf Level 2};

    \node at (-4,30.5) {%
      \begin{minipage}{25cm}
          \begin{itemize}
            \item lattice and symmetry \\
              \minibox{
                \smalltag{\_cell\_length\_\{a,b,c\}} \\
                \smalltag{\_cell\_angle\_\{alpha,beta,gamma\}} \\
                \smalltag{\_symmetry\_space\_group\_name\_\{H-M,Hall\}} \\
                \smalltag{...}
              }
            \item atomic coordinates \\
              \minibox{
                \smalltag{\_atom\_site\_fract\_\{x,y,z\}} \\
                \smalltag{...}
              }
            \item bibliography reference \\
              \minibox{
                \smalltag{\_journal\_\{name\_full,paper\_doi\}} \\
                \smalltag{...}
              }
          \end{itemize}
      \end{minipage}
    };

    \node at (-4,14.5) {%
      \begin{minipage}{25cm}
          \begin{itemize}
            \item computational setup \& parameters \\
              \minibox{
                \smalltag{\_tcod\_software\_\{package,compiler,library\}} \\
                \smalltag{\_tcod\_software\_runtime\_\{CPU,OS\}} \\
                \smalltag{\_dft\_\{XC\_functional,basisset,pseudopotential\}\_type} \\
                \smalltag{...}
              }
            \item residual forces on atoms and cell \\
              \minibox{
                \smalltag{\_tcod\_atom\_site\_residual\_force\_fract\_\{x,y,z\}} \\
                \smalltag{...}
              }
            \item code-specific convergence criteria \\
              \minibox{
                \smalltag{\_dft\_cell\_\{energy,density,potential\}\_conv} \\
                \smalltag{...}
              }
          \end{itemize}
      \end{minipage}
    };

    \node at (-4,-0.5) {%
      \begin{minipage}{25cm}
          \begin{itemize}
            \item input scripts and files \\
              \minibox{
                \smalltag{\_tcod\_file\_\{name,URI,contents,role,interpreter\}} \\
                \smalltag{...}
              }
            \item command line \\
              \minibox{
                \smalltag{\_tcod\_computation\_\{command,environment\}} \\
                \smalltag{...}
              }
            \item output logs of the code \\
              \minibox{
                \smalltag{\_tcod\_computation\_\{log\_file,stdout,stderr\}} \\
                \smalltag{...}
              }
          \end{itemize}
      \end{minipage}
    };

  \end{tikzpicture}
\end{figure}
\vskip -0.5cm
