add shifting darkness to page border

bind.sty

@@ -45,9 +45,12 @@
 \addtocounter{chapshift}{-1}
 
 \newcommand\pageSideColor{%
-	black!25%
+	black!\arabic{pageDarkness}%
 }
 
+\newcounter{pageDarkness}
+\setcounter{pageDarkness}{15}
+
 \newcommand\ChapFrame{%
   \AddEverypageHook{%
     \ifodd\value{page}
@@ -55,14 +58,14 @@
         \begin{tikzpicture}[overlay,remember picture]
           \node[
             fill=\pageSideColor,
-            inner sep=1pt,
+            inner sep=5pt,
             rectangle,
-            text width=1.7cm,
+            text width=1.2cm,
             text height=4cm,
             align=center,
             anchor=north east
           ]
-          at ($ (current page.north east) + (-0cm,-2*\thechapshift cm) $)
+          at ($ (current page.north east) + (-0cm,-2.7*\thechapshift cm) $)
           {\rotatebox{90}{\hspace*{.3cm}\parbox[c][1.5cm][t]{3.4cm}{%
               \raggedright\textcolor{black}{\scshape\leftmark}}}};
         \end{tikzpicture}%
@@ -73,14 +76,14 @@
         \begin{tikzpicture}[overlay,remember picture]
         \node[
           fill=\pageSideColor,
-          inner sep=1pt,
+          inner sep=5pt,
           rectangle,
-          text width=1.7cm,
+          text width=1.2cm,
           text height=4cm,
           align=center,
           anchor=north west
         ]
-        at ($ (current page.north west) + (-0cm,-2*\thechapshift cm) $)
+        at ($ (current page.north west) + (-0cm,-2.7*\thechapshift cm) $)
         {\rotatebox{90}{\hspace*{.3cm}\parbox[c][1.5cm][t]{3.4cm}{%
             \raggedright\textcolor{black}{\scshape\leftmark}}}};
         \end{tikzpicture}%
@@ -89,6 +92,7 @@
     \fi
   \BgMaterial}%
   \stepcounter{chapshift}%
+  \addtocounter{pageDarkness}{7}
 }
 
 % redefinition of \chaptermark to contain only the title