By Christopher Swenson, Twilio Inc.

Adventure was the first text adventure and the first interactive fiction game, and one of the first viral games.

Just text anything to +1 (669) 238-3683 ("669 ADVENT3") to start a game. Send RESET to restart the game. Case doesn't matter when sending commands.

There are four primary components to this software:

• advdat.77-03-31.txt – The 1977 Adventure data file
• advf4.77-03-31.txt – The 1977 Adventure source code (in FORTRAN IV)
• interpret.py – A FORTRAN IV interpreter, written in Python 2.7, that supports the PDP-10 architecture.
• server.py – A web server that connects the FOTRAN interpreter to the Twilio API and to a database to store user data.

Essentially, we run the FORTRAN source code through our interpreter, and when the code requests input from the teletype, we instead feed it the last command sent via Twilio SMS. If there is no command buffered up, the interpreter sleeps, and waits to be woken up when there is a command. Any teletype output is sent to the user via Twilio SMS.

The entire state of the FOTRAN interpreter is pickled (serialized), compressed, and sent to the database after every command is processed. This is about 18 KB per player.

The original source code was written in (the now obsolete) FORTRAN IV, which is no longer supported by any modern compilers. In addition, it was written for the PDP-10 (released in 1966), whose FORTRAN IV variant had a lot of quirks, which make using the old source code challenging.

Some of the fun quirks:

• The PDP-10 is a 36-bit machine.
• It supports a very old version of ASCII, possibly 1963 or 1965.
• It supports character types by packing 5 7-bit ASCII characters into a 36-bit word. The least significant bit is left as a zero, and they are packed "left-to-right" inside the word.
• It is meant to read from disk, tape drive, or teletype, and write to a teletype. So we have to provide emulation for these.

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