diff --git a/src/data/hills.cpp b/src/data/hills.cpp
index 6ba189e..f42b450 100644
--- a/src/data/hills.cpp
+++ b/src/data/hills.cpp
@@ -19,3 +19,4 @@ unsigned const char *hills[] = {
         kulle_6_png,
         kulle_7_png,
 };
+extern const size_t hills_length = 8;
diff --git a/src/data/hills.hpp b/src/data/hills.hpp
index da675ea..53ec66f 100644
--- a/src/data/hills.hpp
+++ b/src/data/hills.hpp
@@ -1,3 +1,4 @@
 #pragma once
 
-extern unsigned const char *hills[];
\ No newline at end of file
+extern unsigned const char *hills[];
+extern const size_t hills_length;