I have taught that the elements are: space, obstacles, goals, mechanics and rules. I know there's no agreed upon set, but other than balance, what other principles might complete the set?

Goals are usually accompanied by Reward, something that provides incentive for working toward said goal.  That little dopamine hit that we’ve all gone scrambling for!

I'm impressed, you actually managed to take the fun out of game design. When designing games you should ask yourself if the idea you have would be fun and how it would affect the game experience, then all those things you talk about (space, obstacles, goals, mechanics, rules etc) will come naturally. You shouldn't try to make games the same way you would build a machine (by the book, using precise measurements and specific parts that go together in a specific way), you should use your experience to know how to put things together and make the game fun to play (because that is the purpose of a game). Play a lot of games and learn as much as possible from them and if you don't like playing games you should look for a job in another field.

3 hours ago, random_user2018 said:

When designing games you should ask yourself if the idea you have would be fun and how it would affect the game experience, then all those things you talk about (space, obstacles, goals, mechanics, rules etc) will come naturally.

Can you give an example of how this workflow has benefited you in one of your game designs?

1 hour ago, fleabay said:

Can you give an example of how this workflow has benefited you in one of your game designs?

Exactly. This person clearly has no idea how you teach game design. By the way, I'm still looking for the principles. I would say some are balance, chance and progression. I also assume they come out of different ways that the elements (rules, mechanics, obstacles, goals and space) interact.

Actually, successful experienced designers do tend to use formal methodologies along with an iterative process to refine their work.  Playing games is fun, that doesn't mean there can't be formal process to design or that designing a game will always be fun.  Designing purely by feel or instinct will likely be less reliable than following a process, and there's nothing wrong with trying to analyze games or design to improve your understanding.

Have you considered things such as the MDA (Mechanics-Dynamics-Aesthetics) framework?  Read a bit about it on Wikipedia.

Daniel Cook describes a system using "skill chains" and "design atoms" in his Chemistry of Game Design, and expanded on this with the idea of loops and arcs.  Keith Burgun has written a bit about arcs in strategy games that's also a good read.

In his book The Art of Game Design: A Book of Lenses, Jesse Schell describes a series of "lenses" through which a design can be examined or approached.

If you haven't read it, Ralph Koster's A Theory of Fun is also commonly recommended reading for would be designers.

Hope that helps!

7 hours ago, fleabay said:

Can you give an example of how this workflow has benefited you in one of your game designs?

Games are designed not engineered. Not using templates gives you creative freedom and it makes it easier to design games. Following a predetermined path takes the focus away from what matters in a game, fun and you end up making bland generic games (titan siege, revelation online, kritika online, c9, vindictus, etc). You cant take the same approach when making a game as you would  building a robot. Game design is closer to art than it is to science, it has more to do with creativity than it has to do with logic. I can't think of any examples of how this workflow has helped me but if u think u can prove me wrong go ahead.  

29 minutes ago, random_user2018 said:

Games are designed not engineered.

Design does not preclude formal methodology or rational analysis, and can in fact be strengthened by those things.

No one is suggesting you need to follow some formula exactly -- I think we all agree that would produce bland cookie cutter games -- but that doesn't mean you can't or shouldn't think about things like mechanical interactions, design space, goals, rules, etc.  In fact, many successful designers recommend doing exactly that. I listed a couple above.

There's no reason you can't be both creative and logical, and the best gameplay tends to emerge from deep understandings of gameplay systems and are the polished result of iterative development; a very logical (but still creative) process.

Graphic Designers understand colour theory, vanishing points, and all sorts of logical elements that go in to their work.

Likewise for just about any other field with a "design" title; there is always a solid understanding of theory and established methodologies.

I'm not clear why you think the same wouldn't apply to game design.

And I might add, if you are teaching high school students, you need a very methodical approach, where all the pieces are broken down and defined. My students understand the elements. The way those elements interact defines the principles. I just need a list of those principles to help me in my lesson planning. So far nobody has provided a distinct list. 

I have read Schell and Koster, but I am looking for something simpler as far as distinct principles that come out of the interaction of space, mechanics, rules, obstacles and goals. Maybe "fun" is a principle? I'm not sure.