gnu: Add pipewalker.

* gnu/packages/games.scm (pipewalker): New public variable.

gnu/packages/games.scm

@@ -793,6 +793,46 @@ (define-public nethack
       (license:fsdg-compatible
         "https://nethack.org/common/license.html"))))
 
+(define-public pipewalker
+  (package
+    (name "pipewalker")
+    (version "0.9.4")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append "http://downloads.sourceforge.net/pipewalker/"
+                           name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "1x46wgk0s55562pd96cxagxkn6wpgglq779f9b64ff1k3xzp3myn"))))
+    (build-system gnu-build-system)
+    (arguments
+     `(#:configure-flags
+       (list (string-append "--docdir=" (assoc-ref %outputs "out")
+                            "/share/doc/" ,name "-" ,version))
+       #:phases
+       (modify-phases %standard-phases
+         (add-after 'configure 'patch-docdir
+           ;; Makefile.in ignores configure's ‘--docdir=...’ option.  Fix that.
+           (lambda _
+             (substitute* "Makefile"
+               (("(pkgdocdatadir = ).*" _ assignment)
+                (string-append assignment "$(docdir)\n")))
+             #t)))))
+    (inputs
+     `(("libpng" ,libpng)
+       ("mesa" ,mesa)
+       ("sdl" ,sdl)))
+    (home-page "http://pipewalker.sourceforge.net/")
+    (synopsis "Logical tile puzzle")
+    (description
+     "PipeWalker is a simple puzzle game with many diffent themes: connect all
+computers to one network server, bring water from a source to the taps, etc.
+The underlying mechanism is always the same: you must turn each tile in the
+grid in the right direction to combine all components into a single circuit.
+Every puzzle has a complete solution, although there may be more than one.")
+    (license license:gpl3+)))
+
 (define-public prboom-plus
   (package
    (name "prboom-plus")