$NetBSD$

--- makefile.orig	2022-10-09 06:17:14.000000000 +0000
+++ makefile
@@ -1,4 +1,4 @@
-PREFIX = /usr/local
+PREFIX? = /usr/local
 MANDIR = $(PREFIX)/share/man
 
 sssnake: main.c autopilot.c xymap.c structs.c snake.c draw.c