Tag: published on gemini

This blog post is also available as a video. Would you prefer to watch/listen to me tell you about the video game that had the biggest impact on my life?

Of all of the videogames I’ve ever played, perhaps the one that’s had the biggest impact on my life¹ was: Werewolves and (the) Wanderer.²

This simple text-based adventure was originally written by Tim Hartnell for use in his 1983 book Creating Adventure Games on your Computer. At the time, it was common for computing books and magazines to come with printed copies of program source code which you’d need to re-type on your own computer, printing being significantly many orders of magnitude cheaper than computer media.³

I’d been working my way through the operating manual for our microcomputer, trying to understand it all.⁵

In particular, I found myself comparing Werewolves to my first attempt at a text-based adventure. Using what little I’d grokked of programming so far, I’d put together a series of passages (blocks of PRINT statements⁶) with choices (INPUT statements) that sent the player elsewhere in the story (using, of course, the long-considered-harmful GOTO statement), Choose-Your-Own-Adventure style.

Werewolves was… better.

Werewolves and Wanderer was my first lesson in how to structure a program.

Let’s take a look at a couple of segments of code that help illustrate what I mean (here’s the full code, if you’re interested):

10 REM WEREWOLVES AND WANDERER

20 GOSUB 2600:REM INTIALISE
30 GOSUB 160
40 IF RO<>11 THEN 30

50 PEN 1:SOUND 5,100:PRINT:PRINT "YOU'VE DONE IT!!!":GOSUB 3520:SOUND 5,80:PRINT "THAT WAS THE EXIT FROM THE CASTLE!":SOUND 5,200
60 GOSUB 3520
70 PRINT:PRINT "YOU HAVE SUCCEEDED, ";N$;"!":SOUND 5,100
80 PRINT:PRINT "YOU MANAGED TO GET OUT OF THE CASTLE"
90 GOSUB 3520
100 PRINT:PRINT "WELL DONE!"
110 GOSUB 3520:SOUND 5,80
120 PRINT:PRINT "YOUR SCORE IS";
130 PRINT 3*TALLY+5*STRENGTH+2*WEALTH+FOOD+30*MK:FOR J=1 TO 10:SOUND 5,RND*100+10:NEXT J
140 PRINT:PRINT:PRINT:END

...

2600 REM INTIALISE
2610 MODE 1:BORDER 1:INK 0,1:INK 1,24:INK 2,26:INK 3,18:PAPER 0:PEN 2 
2620 RANDOMIZE TIME
2630 WEALTH=75:FOOD=0
2640 STRENGTH=100
2650 TALLY=0
2660 MK=0:REM NO. OF MONSTERS KILLED

...

3510 REM DELAY LOOP
3520 FOR T=1 TO 900:NEXT T
3530 RETURN

What’s interesting about the code above? Well…

• The code for “what to do when you win the game” is very near the top. “Winning” is the default state. The rest of the adventure exists to obstruct that. In a language with enforced line numbering and no screen editor⁷, it makes sense to put fixed-length code at the top… saving space for the adventure to grow below.
• Two subroutines are called (the GOSUB statements):
  • The first sets up the game state: initialising the screen (2610), the RNG (2620), and player characteristics (2630 – 2660). This also makes it easy to call it again (e.g. if the player is given the option to “start over”). This subroutine goes on to set up the adventure map (more on that later).
  • The second starts on line 160: this is the “main game” logic. After it runs, each time, line 40 checks IF RO<>11 THEN 30. This tests whether the player’s location (RO) is room 11: if so, they’ve exited the castle and won the adventure. Otherwise, flow returns to line 30 and the “main game” subroutine happens again. This broken-out loop improving the readability and maintainability of the code.⁸
• A common subroutine is the “delay loop” (line 3520). It just counts to 900! On a known (slow) processor of fixed speed, this is a simpler way to put a delay in than relying on a real-time clock.

The game setup gets more interesting still when it comes to setting up the adventure map. Here’s how it looks:

2680 REM SET UP CASTLE
2690 DIM A(19,7):CHECKSUM=0
2700 FOR B=1 TO 19
2710   FOR C=1 TO 7
2720     READ A(B,C):CHECKSUM=CHECKSUM+A(B,C)
2730   NEXT C:NEXT B
2740 IF CHECKSUM<>355 THEN PRINT "ERROR IN ROOM DATA":END

...

2840 REM ALLOT TREASURE
2850 FOR J=1 TO 7
2860   M=INT(RND*19)+1
2870   IF M=6 OR M=11 OR A(M,7)<>0 THEN 2860
2880   A(M,7)=INT(RND*100)+100
2890 NEXT J

2910 REM ALLOT MONSTERS
2920 FOR J=1 TO 6
2930   M=INT(RND*18)+1
2940   IF M=6 OR M=11 OR A(M,7)<>0 THEN 2930
2950   A(M,7)=-J
2960 NEXT J
2970 A(4,7)=100+INT(RND*100)
2980 A(16,7)=100+INT(RND*100)

...

3310 DATA   0,  2,  0,  0,  0,  0,  0
3320 DATA   1,  3,  3,  0,  0,  0,  0
3330 DATA   2,  0,  5,  2,  0,  0,  0
3340 DATA   0,  5,  0,  0,  0,  0,  0
3350 DATA   4,  0,  0,  3, 15, 13,  0
3360 DATA   0,  0,  1,  0,  0,  0,  0
3370 DATA   0,  8,  0,  0,  0,  0,  0
3380 DATA   7, 10,  0,  0,  0,  0,  0
3390 DATA   0, 19,  0,  8,  0,  8,  0
3400 DATA   8,  0, 11,  0,  0,  0,  0
3410 DATA   0,  0, 10,  0,  0,  0,  0
3420 DATA   0,  0,  0, 13,  0,  0,  0
3430 DATA   0,  0, 12,  0,  5,  0,  0
3440 DATA   0, 15, 17,  0,  0,  0,  0
3450 DATA  14,  0,  0,  0,  0,  5,  0
3460 DATA  17,  0, 19,  0,  0,  0,  0
3470 DATA  18, 16,  0, 14,  0,  0,  0
3480 DATA   0, 17,  0,  0,  0,  0,  0
3490 DATA   9,  0, 16,  0,  0,  0,  0

What’s this code doing?

• Line 2690 defines an array (DIM) with two dimensions⁹ (19 by 7). This will store room data, an approach that allows code to be shared between all rooms: much cleaner than my first attempt at an adventure with each room having its own INPUT handler.
• The two-level loop on lines 2700 through 2730 populates the room data from the DATA blocks. Nowadays you’d probably put that data in a separate file (probably JSON!). Each “row” represents a room, 1 to 19. Each “column” represents the room you end up at if you travel in a given direction: North, South, East, West, Up, or Down. The seventh column – always zero – represents whether a monster (negative number) or treasure (positive number) is found in that room. This column perhaps needn’t have been included: I imagine it’s a holdover from some previous version in which the locations of some or all of the treasures or monsters were hard-coded.
• The loop beginning on line 2850 selects seven rooms and adds a random amount of treasure to each. The loop beginning on line 2920 places each of six monsters (numbered -1 through -6) in randomly-selected rooms. In both cases, the start and finish rooms, and any room with a treasure or monster, is ineligible. When my 8-year-old self finally deciphered what was going on I was awestruck at this simple approach to making the game dynamic.
• Rooms 4 and 16 always receive treasure (lines 2970 – 2980), replacing any treasure or monster already there: the Private Meeting Room (always worth a diversion!) and the Treasury, respectively.
• Curiously, room 9 (the lift) defines three exits, even though it’s impossible to take an action in this location: the player teleports to room 10 on arrival! Again, I assume this is vestigal code from an earlier implementation.
• The “checksum” that’s tested on line 2740 is cute, and a younger me appreciated deciphering it. I’m not convinced it’s necessary (it sums all of the values in the DATA statements and expects 355 to limit tampering) though, or even useful: it certainly makes it harder to modify the rooms, which may undermine the code’s value as a teaching aid!

Something you might notice is missing is the room descriptions. Arrays in this language are strictly typed: this array can only contain integers and not strings. But there are other reasons: line length limitations would have required trimming some of the longer descriptions. Also, many rooms have dynamic content, usually based on random numbers, which would be challenging to implement in this way.

As a child, I did once try to refactor the code so that an eighth column of data specified the line number to which control should pass to display the room description. That’s a bit of a no-no from a “mixing data and logic” perspective, but a cool example of metaprogramming before I even knew it! This didn’t work, though: it turns out you can’t pass a variable to a Locomotive BASIC GOTO or GOSUB. Boo!¹⁰

Werewolves and Wanderer has many faults¹¹. But I’m clearly not the only developer whose early skills were honed and improved by this game, or who hold a special place in their heart for it. Just while writing this post, I discovered:

• A moderately-faithful Inform reimplementation
• A less-faithful semi-graphical adaptation
• A C# reimplementation with a web interface (video)
• An ongoing livestreamed effort to reimplement as a Sierra-style point-and-click adventure
• An Applesoft BASIC implementation which includes a dynamically-revealed map
• A C reimplementation with a high score table
• A somewhat-faithful reimplementation in Rust (playable online via WebAssembly)
• A very accurate rendition in Python
• A Ruby/Python microservices-based implementation
• Many, many people commenting on the above or elsewhere about how instrumental the game was in their programming journey, too.

A decade or so later, I’d be taking my first steps as a professional software engineer. A couple more decades later, I’m still doing it.

And perhaps that adventure -the one that’s occupied my entire adult life – was facilitated by this text-based one from the 1980s.