diff --git a/index.html b/index.html
index d0c33840..b882fa91 100644
--- a/index.html
+++ b/index.html
@@ -394,6 +394,7 @@
         // name - display name of the element
         // color - color of the element's pixel *
         // behavior - behavior of the element *
+        // category - category in which the element will show up in
         // density - density of the element [only used for movable elements] (kg/m^3)
         // state - solid, liquid, or gas [only used for movable elements]
         // conduct - conductivity of the element (0-1)