diff --git a/api_docs/doctrees/environment.pickle b/api_docs/doctrees/environment.pickle
index 702abc43..9632715b 100644
Binary files a/api_docs/doctrees/environment.pickle and b/api_docs/doctrees/environment.pickle differ
diff --git a/css/extra.css b/css/extra.css
index a6fdfea0..7de8f895 100644
--- a/css/extra.css
+++ b/css/extra.css
@@ -1,39 +1,71 @@
+/* extra.css */
+
 .center {
     display: block;
     margin: 0 auto;
 }
 
-:root {
+/* nervosys: light mode */
+[data-md-color-scheme="nervosys_light"] {
 
     /* primary color shades */
+    /* violet: #5000cd, magenta: #ff008a, seafoam: #00ffcd */
     --md-primary-fg-color: #5000cd;
-    --md-primary-fg-color--light: #5000cd;
-    --md-primary-fg-color--dark: #ff008a;  /* #00ffcd */
+    --md-primary-fg-color--light: #ff008a;
+    --md-default-bg-color: #ffffff;
     --md-primary-bg-color: hsla(0, 0%, 100%, 1);
     --md-primary-bg-color--light: hsl(0, 0%, 100%);
-    --md-primary-bg-color--dark: hsl(0, 0%, 0%);
     --md-text-link-color: hsla(168, 100%, 50%, 1);
 
     /* accent color shades */
-    --md-accent-fg-color: rgb(98, 18, 189);
+    --md-accent-fg-color: rgb(80, 0, 205);
     --md-accent-fg-color--transparent: hsla(189, 100%, 37%, 0.1);
     --md-accent-bg-color: hsla(0, 0%, 100%, 1);
     --md-accent-bg-color--light: hsla(0, 0%, 100%, 0.7);
-    --md-accent-bg-color--dark: hsla(0, 0%, 100%, 0.3);
 }
-  
-:root > * {
+
+[data-md-color-scheme="nervosys_light"] > * {
   
     /* code block color shades */
     --md-code-bg-color: hsla(0, 0%, 96%, 1);
     --md-code-fg-color: hsla(200, 18%, 26%, 1);
 
-    /* footer color shades */
+    /* footer */
+    --md-footer-bg-color: #861f41;
+    --md-footer-bg-color--light: hsla(0, 0%, 0%, 0.32);
     --md-footer-fg-color: hsla(0, 0%, 100%, 1);
     --md-footer-fg-color--light: hsla(0, 0%, 100%, 0.7);
     --md-footer-fg-color--lighter: hsla(0, 0%, 100%, 0.3);
-    --md-footer-fg-color--dark: hsla(0, 0%, 100%, 1);
+}
+
+/* nervosys: dark mode */
+[data-md-color-scheme="nervosys_dark"] {
+
+    /* primary color shades */
+    --md-primary-fg-color: #ff008a;
+    --md-primary-fg-color--dark: #00ffcd;
+    --md-default-bg-color: #000000;
+    --md-primary-bg-color: hsl(0, 0%, 0%);
+    --md-primary-bg-color--dark: hsl(0, 0%, 0%);
+    --md-text-link-color: hsla(168, 100%, 50%, 1);
+
+    /* accent color shades */
+    --md-accent-fg-color: rgb(80, 0, 205);
+    --md-accent-fg-color--transparent: hsla(189, 100%, 37%, 0.9);
+    --md-accent-bg-color: hsla(0, 0%, 100%, 1);
+    --md-accent-bg-color--dark: hsla(0, 0%, 100%, 0.7);
+}
+
+[data-md-color-scheme="nervosys_dark"] > * {
+  
+    /* code block color shades */
+    --md-code-bg-color: hsla(0, 0%, 96%, 1);
+    --md-code-fg-color: hsla(200, 18%, 26%, 1);
+
+    /* footer */
     --md-footer-bg-color: #861f41;
-    --md-footer-bg-color--light: hsla(263, 100%, 40%, 1);
-    --md-footer-bg-color--dark: hsla(328, 100%, 50%, 1);
+    --md-footer-bg-color--dark: hsla(0, 0%, 0%, 0.32);
+    --md-footer-fg-color: hsla(0, 0%, 100%, 1);
+    --md-footer-fg-color--dark: hsla(0, 0%, 100%, 0.7);
+    --md-footer-fg-color--darker: hsla(0, 0%, 100%, 0.3);
 }
diff --git a/sitemap.xml.gz b/sitemap.xml.gz
index a54cd05d..9a76c410 100644
Binary files a/sitemap.xml.gz and b/sitemap.xml.gz differ