$OpenBSD: patch-src_ball_h,v 1.1 2019/01/01 17:59:05 landry Exp $
ball.h:113:19: error: 'NULL' was not declared in this scope
Index: src/ball.h
--- src/ball.h.orig
+++ src/ball.h
@@ -25,6 +25,7 @@
 class ball;
 
 #include "square.h"
+#include <cstddef>
 
 class ball_base
 {
