If you want to play the original Spacewar! but you don’t have a PDP-1 nearby, then you’re in luck — assuming you have a PDP-11, that is. [Mattis Lind] has successfully restored a PDP-11 port of the game from PDF scans of the source code, which was thought to have been lost to the trash bins of DECUS (Digital Equipment Computer Users’ Society). Fortunately, [Mattis] learned that [Bill Seiler], one of the original authors, had saved a printout of the assembly language. 
Using a combination of OCR and manual transcription to retrieve the code, [Mattis] took a deep dive into cleaning up the errors and solving a whole lot of system library and linking issues. Adding to the difficulty is that his PDP-11 is slightly different from the one used in 1974 when this port was written.
The project was not all software — [Mattis] also needed to make a pair of joysticks, which he made from a handful of items found on AliExpress. As you can see in the video below, he indeed got it all working. [Mattis] is no stranger to the PDP-11 world. We wrote about his PDP-11 restoration project back in 2015, a quest that took over 18 months.
I remember this game. Or at least, I think I do. Wasn’t there a video-game console version of it made briefly? Pre-Atari, or thereabouts? I found a web site with the information about it. I remember playing it as a kid, but it wasn’t really all that exciting (sorry :-) But it was new and different.
http://www.andysarcade.de/spacewars.html
Probably you mean this machine: https://en.m.wikipedia.org/wiki/Vectrex
No, I’ve seen the Vetrex before. Can’t recall if I’ve actually played one or not. But the one I linked to above was the one– though I don’t know if there was a difference between a “German” on and an “American” one (presuming there even is a difference, simply because the website is german, *.de). I remember a friend and I stumbled across it set up at the train station and it was very interesting and unique at the time. But expensive, requiring $0.50 each for us to play it together. So we didn’t play it more than a few times.
What’s that HP vector display he’s using?
It’s an HP 1332A X-Y display. (An oscilloscope without the oscillo part.)
Will the pdp-11 port work on emulated hardware? This is cool but I haven’t touched a real pdp-11 since the 1980s
The input (analog joysticks & buttons) and output (x/y scope) devices will be the tricky part.
I remember playing this on a mainframe at UBC back in the mid 70’s. Would have been a variant of it of course, as I’m pretty sure it wasn’t a DEC machine. Recall having to use a paper tape to do the initial boot. Was a huge machine in it’s own air con room.
We had a DEC GT40 (PDP-11/05, VT40) that would bootstrap from the host PDP-11/40 at Auburn University, Electrical Engineering Department. Lunar Lander and SpaceWar were very popular ways to pass the time. An A/D module was used for the two ‘controllers’ to play SpaceWar and a lightpen was used for Lunar Lander. This was late 1970s. The PDP 11/40 had Tektronix displays (all serial connections back then, DH11’s) and various games too were played on them. Golf was the most popular. The PDP-11/40 ran RSTS/e, an amazing O/S. Great job on the work Sir!
I played this game on a decwriter in ~1976. Is there a command line version of that??