Interview: John Calhoun on the Origins of Glider (Part 1)

mossy_11 on Saturday, 27 November 2010. Posted in Mac Classics Reborn


John Calhoun's Glider games hold a special place in the history of Mac gaming, acting almost as an icon of the platform through much of the 1990s. They spawned a hugely dedicated fan base, which produced a ridiculous amount of original content both for and about Glider -- especially Glider 4 and Glider PRO, the later versions.

I caught up with Calhoun over email recently, and quizzed him on the origins and development of the series. This is the first part of that interview. Read on to discover where the idea for Glider originated, how the game came to exist, and how it dramatically altered Calhoun's future.

And also be sure to check out Dreaming of a Thousand-Room House: The History and Making of Glider, which provides context and a narrative for this interview.

Richard Moss: What inspired you to start programming?


2001-a_space_odysseyJohn Calhoun: I can't say for sure. Growing up, computers were a part of science fiction culture. I associated computers with things futuristic, technical — and these things interested me when I was young. Movies I enjoyed, like 2001: A Space Odyssey, and T.V. shows I was drawn to, like the original Star Trek, portrayed computers in this way.

Programming was interesting for a number of reasons, though. There was a certain exploration aspect to it. You knew that there was a lot of potential locked up in the hardware (the computer), and this often helped to draw me further into learning new tricks in software in order to better exploit the machine. Games for the devices showed you that the machine could produce sound, display animated graphics, etc. So when I was just starting to learn to program it was perhaps the technology demonstrated by the computer games that seemed so elusive and out of reach.

Back then, though, I was learning to program in BASIC, so there was no way I was going to be able to write a game that could blit as fast as the commercial hand-coded-assembly games. Still, simple BASIC programs that would render geometric shapes using move-to and line-to calls were in subtle ways teaching me about how a computer displays graphics and such.

I did very quickly come to want to write computer games, though. Since I enjoyed drawing and other art-related things at that time, it may be that I saw games as bridging the artistic and creative pursuits with those more technical. I also felt like I had some ideas for games that I would like to see written.

And finally, I enjoyed playing games in the arcades at the time (games like DefenderJoust, etc.), but I didn't have enough spare change to play them nearly as much as I would have liked. A computer game that you write is ostensibly free.

RM: I’ve read that a very early version of Glider was made on a Commodore VIC-20, but you tried making games before that, and there was a sizable period of time wherein you explored other ideas before you returned to Glider. Could you tell me a little about this time? What came out of these early computing and programming experiences, and how did they impact on your interest in games and digital graphics?

JC: A friend had a Commodore PET, and it had come with an interesting little game -- written in BASIC -- that vaguely looked like the arcade game Asteroids (or perhaps Frogger is a more accurate comparison). An asterisk ("*") or two was randomly displayed at the bottom of the display, and then the display scrolled one line up. Another random pair of asterisk was then added to the empty line at the bottom of the screen, and it was scrolled up one line again. This repeated such that it appeared as though a random field of asteroids (asterisks) scrolled up the screen. As the player, you controlled a small ship (a less-than symbol, "<") half-way up the screen on the right hand side. Using the keyboard you tried to navigate your small ship across the screen without colliding with an aster-oid/isk.

It was a clever game and we spent many evenings tweaking the game -- making it richer, more complex, and frankly more fun. I was hooked really at that point. The asteroid density increased over time, limited shields were added to protect your ship a few times, an enemy ship would appear after a while to pursue you -- hastening you across the asteroid field.... Lots of fun.

commvic20Later, one summer when staying up in Alaska with my dad, I started playing with his Commodore VIC-20. Tron had been popular, and I had written something similar to the light-cycle game from Tron on my friend's PET. Besides adding color to the game for the VIC-20, I was able to go further still and tweak the character bitmap tables so that instead of your light-cycle in the game being an asterisk or whatever, I could make it look like something more closely resembling the light-cycles from the movie. (This was done by essentially redefining what the text characters looked like when displayed on screen.)

Again too, I had hours and hours of fun adding richness to the basic light-cycle game: adding a teleportation option that you could use once to randomly place you somewhere else on the screen, having enemies with different "A.I.'s" (so to speak) — the harder ones you would encounter as the game progressed. It was enjoyable beyond its technical trappings — it was fun trying to make the game fun. It was fun creatively.

Glider saw its origins as a sort of experiment around that time. By redefining that bitmap tables for the characters, I had basically a blower vent (made up perhaps of two different characters placed side by side to appear as a single wide graphic) and a triangular dart-like paper airplane. The physics of the plane rising when over the vent and then falling when not over the vent was strangely fun to play with. It wasn't a game to speak of at that time, but it was still amusing for some reason — to just rise and fall and pace across the screen in this fashion. Mentally I filed it away.

RM: Any idea what made you think to try that experiment?

JC: Probably two things inspired that idea.

s_Choplifter_6The simple answer is that I had played Choplifter on the Atari 2600 and was really impressed with it. I liked the way it was a side-scroller, not unlike one of my arcade favorites: Defender. So in my Commodore exercise, it became a paper airplane you could move left and right, side-scroller style. I suppose the twist I added was the lack of direct vertical control — you needed to find things for lift (the vents) to get altitude, gravity took care of your coming back down....

The other inspiration was probably my playing with paper airplanes as a kid. There was a mall my friends and I would ride our bikes to that had a large air conditioning unit outside. The air conditioner had a large powerful fan that was mounted on top of the unit and blew straight up. Standing on a ledge over the unit one day, I began launching things over it and watching them get lift from the column of air blowing out. At first I found small cup-shaped foam packing peanuts to drop on the column of air. Then I started folding paper helicopters and airplanes and tossing them out over the unit to watch them float and rise on the column of air.

At other times, I would find places with an updraft (balconies on tall buildings for example) and could amuse myself for hours with bubbles, paper helicopters or paper airplanes. So this sort of thing was in my DNA. :-)

RM: When did you return to the air vent and paper plane concept? What made you think it would work as the core mechanic for a game?

JC: When I got my first Macintosh in college, it was clear I was going to have to learn to program it. After learning the Pascal programming language and getting my own little “Hello World” app up and running, I turned, as usual, to trying to write a game for the computer.

One of the things I learned early on was how to draw an arbitrary bitmap on the screen and animate it. When I could move an image on screen, following your mouse cursor for example, I began to kick around ideas for a game to try and write for the Mac.

This is when the paper airplane and blower vent came to mind again. I already had the skills needed to implement this same little demo on the Mac, and with the nice bitmap graphics I could make a much nicer version than the trifle I had done on the Commodore. So I set about drawing a small paper airplane with MacPaint and a small air vent, like you might see in a house, and brought this artwork into my first attempt at a Macintosh game.

Throw in some background art that resembles a room, determine when the glider is over a vent and lift the glider, add some collision detection so that the game ends when the glider lands on the floor — you can see how very quickly you get to the fundamentals of what Glider turned out to be. And like the Commodore experiment, I found this new one fairly amusing to play around with as well.

When I considered what I would do to make a proper game out of it, it occurred to me that perhaps I could add an obstacle that you had to avoid, like a shelf. So with clever placement of shelves and floor vents, you could make a sort of puzzle or a kind of obstacle course that the player had to maneuver their glider through. Once I had a few tables and shelves, it became clear in playing around with it that it was kind of fun.

Once I had the bones of the game, and believed it would be fun, the real enjoyable part of developing a game began. Now it becomes fun to just let your imagination go and consider other obstacles that might add challenges to the game. How about stringing the rooms together to create a house the player has to get through? How about ducts that connect to other parts of the house? How about a candle? Electrical outlets that periodically zap....

You can see how the game can sort of write itself though once you get the seed of a game germinated.

RM: So Glider kind of grew organically into a proper game -- as opposed to being planned out on paper first. Would you say there was much of an iterative process, where you continually tweaked the existing mechanics and level design whilst experimenting with the ideas individually? Or was it more like you just dumped a lot of ideas in at once, then set about throwing out anything that didn’t work after it was done? I guess what I’m essentially asking is how did your development process work -- beyond the explosion of creativity that brings all those ideas and the initial proof of concept?

JC: There was some iteration with the game physics. How quickly should the glider rise on the air column? How quickly should it fall? How fast should it move forward? These are pretty early and fundamental things I tweaked. Once arrived at, though, I couldn’t change these things — objects arranged in the rooms would require repositioning if suddenly the Glider had a different glide ratio. I tried not to make too much work for myself.

I think once I got the physics right, it generally evolved as a new item was added -- one at a time (not all at once). So I add a table, get hit detection working so your glider crashes if it lands on top of the table, and I play with adding tables of various heights in a room and see how that improves the game.

Then I add something like a candle, add some code so the glider can catch fire and then experiment with laying candles in various places in a room.

The game was evolving and growing one object at a time.

At a certain point, though, you’re just looking around the rooms of your apartment and seeing if you missed anything. Ceiling fan? That one didn’t seem like so good a fit for the game. Rug? Maybe as decoration....

I looked for variety too, though. The electrical outlets zapping your glider were a nice addition because they added a timing element to the game. Other items I would add later (like toasters, drips, etc.) would also have a timing element. Switches allowed objects to be turned on and off, and added an almost puzzle element to the game.

A few items were “invented” because I thought the game play needed something to perform a specific task. For example, I wanted to add a few “power-ups” in the game. I thought a power-up that gave you an extra boost would be a useful item to have. So I added the battery object to the game for that purpose. I know it doesn’t make logical sense that a battery would be at all useful to a paper glider, but it was the only thing I could think of.

I think you get the idea: it grew very evolutionarily.

mac-plus-front-535RM: What was your first Mac? When did the Mac Plus make its first appearance within a Glider game? (Glider 1 and 2 were before my time, and I’ve yet to track down a playable copy of either. Glider 2 is available here.) Was it some kind of tribute? I know I’m certainly a fan of the Mac Plus, with it having been my first computer.

JC: My first Mac was the Mac Plus. I still love that machine. Glider 1.0 & 2.0 were shareware and replaced very quickly with Glider 3.0. I don’t even recall what was different in the various early versions. I think I didn’t have sound in 1.0. Perhaps no cat until version 3.0.... In any event, 3.0 was basically the definitive black and white shareware version.

Was the Mac Plus in the shareware version? I don’t remember. Truly, though, this was one of those things where I looked around my room, saw my Mac Plus, and thought to put it in the game. At some point I picked up a MacRecorder (I think it was called) and I was able to digitize/sample live sounds. I sampled my MacPlus booting up to use in Glider. People do generally respond when they hear for the first time the Mac Plus booting up in Glider.

RM: What was the reception like for the first public version of Glider? How was it distributed (e.g. BBS, Usenet, disk)? Did it make you much money?

JC: The reception was pretty good. Looking back at the original B&W version I’m a little surprised, though: the artwork was very uneven — not polished at all.

Since I was at a university at the time, I took advantage of the internet access universities had, and FTP’ed the shareware Glider to various popular Mac FTP sites. Perhaps I don’t remember anymore what the hot Mac FTP sites were. In any event, once you got it to one or two it seemed to just take on a life of its own and migrate from site to site.

Glider2At some point, my girlfriend (wife now) could pretty much count on at least one shareware check a week for Glider. Being starving college kids, I confess that very often we spent the shareware money on a Friday pizza and two large Cokes. It was a real treat back then, though, to be able to get a pizza once a week or so. :-) It sort of helped me sell the idea of my staying up at all hours of the night programming to my girlfriend. Hey, free pizza for both of us, right?

So I wasn’t getting rich by any stretch of the imagination, but the letters were often enthusiastic and gave me the sense that Glider was, to some, a special little game.

RM: How did it feel to get a game out there for the Macintosh? Did you ever really intend to make a career (albeit temporary, given your present arrangements) out of game development?

JC: No, I never intended to make a career out of game development. I was in college majoring in Education. I intended to make a career out of teaching high school. :-)

hackersI have to mention Steve Levy’s book Hackers, though, because it was after having read his book that I decided to make a go at getting Glider published commercially (which then lead to my career change).

Hackers is a great book that tries to cover the creation of “hacker culture.” And by hacker I mean of course someone clever in their use of computers, not hacker in the derogatory sense. The third section of his book covers game development for personal computers — specifically Sierra On-Line (an early Apple II game company). It was impossible not to read about the late night game programming sessions fueled by caffeine and Dungeons and Dragons and not be a little bit envious of those kids. I was in high school when the Apple II game development that Levy writes about happened. As I read his book, I felt a little sad that the action seemed to have already come and gone while I was still learning BASIC. And it had happened in California to boot (about as far from Kansas as you can get).

Still, I thought, “Why don’t I at least try to get published?” Maxis was a new company (SimCity had just come out), so I think I called them (no response). The second company I called was Casady & Green, Inc. — I had seen their game advertisements in MacWorld (Crystal QuestSky Shadow). They tried out the shareware version of Glider and basically said, “Sure.” I would do Glider in color, add more rooms to the house, they would get me a color Macintosh for my development and publish Glider. What a deal.

glider_nesRM: Are you aware of this NES port of Glider 3.0 Glider 4 (my bad.)? It seems crazy that people can play Glider on a console (albeit with a lot of effort).

JC: Yeah, the guy asked permission to do the port. I was pretty impressed with the effort he undertook to do it. He gave me a free copy and an actual NES machine to play it on as well. Very cool.

Check out part 2 here, wherein we discuss community influences, Glider's legacy, the appeal of the Glider concept, and the commercial Glider games -- Glider 4 and Glider PRO.

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