===> Update to 0.4. Changes:
* Added an easy mode (Press 'e' for an easy game).
* Rocks are now totally solid (they bounce off each other and get pushed by your jets).
* Fixed placement of new ships so you're less likely to die multiple times.
* Added explanatory message at game over.
===> Cleanup port
Remove USE_REINPLACE, optimize do-install target, handle PORTDOCS...
You missed inclusion of bsd.port.pre.mk for OSVERSION, though.