X16Community · geneb · Jan 17, 2026 · Jan 17, 2026 · Jan 18, 2026 · Jan 18, 2026
diff --git a/.gh/markdown.css b/.gh/markdown.css
@@ -133,3 +133,43 @@ table tr {
 table tr:nth-child(2n) {
 	background-color: whitesmoke;
 }
+
+/* 
+ * The mark and marksq styles will change the colors of the Markdown highlight feature based on 
+ * the viewer's dark mode settings.  Light mode will get white text on a black background,
+ * and dark mode should get black text on a white background.
+ * It also adds a border radius to the background to give the highlighted items a more
+ * "key-like" look.
+ */
+
+mark { /* gives a rounded "key" look to highlighted items. */
+  background-color: #000000;
+  color: #f5f5f5;
+  border-radius: 5px; 
+  padding: 0 4px; 
+}
+
+/* Dark Mode */
+@media (prefers-color-scheme: dark) {
+  mark {
+    background-color: #f5f5f5;
+    color: #000000;
+    border-radius: 5px; 
+    padding: 0 4px; 
+  }
+}
+
+marksq { /* used to letters with a square background */
+  background-color: #000000;
+  color: #f5f5f5;
+  padding: 0 4px; 
+}
+
+/* Dark Mode */
+@media (prefers-color-scheme: dark) {
+  marksq {
+    background-color: #f5f5f5;
+    color: #000000;
+    padding: 0 4px; 
+  }
+}
diff --git a/X16 Reference - 04 - BASIC.md b/X16 Reference - 04 - BASIC.md
diff --git a/images/norm-lower-bar.png b/images/norm-lower-bar.png
diff --git a/images/print-color-example.png b/images/print-color-example.png
diff --git a/images/print-screen-pos-example.png b/images/print-screen-pos-example.png
diff --git a/images/rvs-E.png b/images/rvs-E.png
diff --git a/images/rvs-H.png b/images/rvs-H.png
diff --git a/images/rvs-I.png b/images/rvs-I.png
diff --git a/images/rvs-N.png b/images/rvs-N.png
diff --git a/images/rvs-Q.png b/images/rvs-Q.png
diff --git a/images/rvs-S.png b/images/rvs-S.png
diff --git a/images/rvs-backslash.png b/images/rvs-backslash.png
diff --git a/images/rvs-ball.png b/images/rvs-ball.png
diff --git a/images/rvs-bar.png b/images/rvs-bar.png
diff --git a/images/rvs-circle.png b/images/rvs-circle.png
diff --git a/images/rvs-club.png b/images/rvs-club.png
diff --git a/images/rvs-diamond.png b/images/rvs-diamond.png
diff --git a/images/rvs-half-tile.png b/images/rvs-half-tile.png
diff --git a/images/rvs-heart.png b/images/rvs-heart.png
diff --git a/images/rvs-l-arr.png b/images/rvs-l-arr.png
diff --git a/images/rvs-l-ramp.png b/images/rvs-l-ramp.png
diff --git a/images/rvs-pi.png b/images/rvs-pi.png
diff --git a/images/rvs-plus-symbol.png b/images/rvs-plus-symbol.png
diff --git a/images/rvs-pound.png b/images/rvs-pound.png
diff --git a/images/rvs-r-bracket.png b/images/rvs-r-bracket.png
diff --git a/images/rvs-r-offset-bar.png b/images/rvs-r-offset-bar.png
diff --git a/images/rvs-slash.png b/images/rvs-slash.png
diff --git a/images/rvs-spade.png b/images/rvs-spade.png
diff --git a/images/rvs-ul-corner.png b/images/rvs-ul-corner.png
diff --git a/images/rvs-up-arr.png b/images/rvs-up-arr.png
diff --git a/images/rvs-ur-corner.png b/images/rvs-ur-corner.png
diff --git a/images/rvs-x-symbol.png b/images/rvs-x-symbol.png