diff --git a/source/index.rst b/source/index.rst
index fa2a8e7..c510124 100644
--- a/source/index.rst
+++ b/source/index.rst
@@ -20,6 +20,7 @@
    13-sky-box-and-some-optimizations
    14-height-maps
    15-terrain-collisions
+   16-fog
 
 本书原介绍
 ****