diff --git a/a8/a8.h b/a8/a8.h
index 77cbcda..40ec32e 100644
--- a/a8/a8.h
+++ b/a8/a8.h
@@ -37,4 +37,6 @@ namespace std
 
 #define A8_ABORT() do{printf("abort file:%s line:%d func:%s\n", __FILE__, __LINE__, __func__);fflush(stdout);fflush(stderr);abort();}while(0);
 
+const float A8_PI = 3.1415926f;
+
 #endif