Dev Journal #116: The Tech Tree in the Room

Tech trees are one of those parts of a strategy game that look obvious from the outside and turn out, every single time, to be one of the hardest things to get right. Game designers have been struggling with how to present technology research to the player since the early 90s, and three decades in, nobody has really solved it. There are good answers, there are interesting answers, and there are answers that work for one game and fall apart in another. There is no settled answer.

As part of the work going into GalCiv IV 4.0, we have been revisiting our tech tree. The question we are sitting with is whether to redo it from scratch or to focus on making the one we have more effective. Both are real options. Both have real costs. We are not done deciding.

Pretty | Easy to Use | Provide Good Gameplay.

Pick 2.

But that doesn’t stop us from trying to have our cake and eat it too. And of course, that means a lot of failure. So much fail.

Why this is hard in the first place

A tech tree is doing more work than it looks like it is doing. It is not just a list of unlocks. It is the spine of the strategic identity of the game. The decisions you make in the first thirty turns of research are not "what gets unlocked next," they are "what kind of game am I playing." If your tree fails at that, no amount of balance work fixes it. If it succeeds at it, players will forgive a startling amount of imbalance.

That is the bar. Two players in the same game, same map, same starting civ. Do they end up feeling like they played different games? If yes, the tree is doing its job. If no, what you have is a checklist with nice art on it.

Then on top of that, the tree has to be legible. It has to be plannable, at least somewhat. It has to survive 500 turns of play without becoming a chore. It has to be teachable to a new player and rewarding to a veteran. It has to scale to hundreds of nodes without turning into wallpaper.

These goals fight each other. Always.

How the genre has tried

Our genre has tried a bunch. Let’s take a tour.

The Civ lattice. Directed graph, eras as horizontal bands. The thing everyone pictures when they hear "tech tree." Strong theater, you really do feel like you have crossed into the Industrial Era. The weakness is that the optimal path crystallizes within months of release, and by Civ V the community had spreadsheeted out the dominant openings to the point that the lattice was largely a memorization exercise.

Master of Orion's tier-and-drop. Each tier offered a few techs and you picked one; the rest were gone for that game. The first 4X I can think of that was honest about the fact that the exclusion is the choice. Two MoO games were not the same game. The cost was that a new player could lock themselves out of something critical without realizing it.

Classic GalCiv parallel tracks. Our own heritage, in various forms, since GalCiv II. Military, economy, diplomacy, social, all advancing in parallel with cross-track prerequisites. It solves the "tech tree is one rail" problem and lets a player visibly be a military civ or a research civ. The honest weakness is that the tracks tend to drift toward feeling like four small linear trees that happen to share a screen.

SMAC's blind research. You set a category bias and the game picked your next tech. The most radical answer in the genre to "the optimal path becomes orthodoxy," because there is no path you control. Beloved by a hardcore niche, hated by everyone who wants agency. I respect it more than any other system on this list and I would not copy it.

Stellaris's card draw. Three weighted options every time you finish a tech, drawn from a pool. The slot machine answer. The dominant build cannot exist if the build is not replicable. The cost is planning. You cannot say "in twenty turns I will have X" because the deck might not deal it. Some players love this. Some bounce off it in the first hour.

Beyond Earth's web. No clear forward, no era bands, total radial freedom. The designers were trying to make every game feel different by removing the spine. The community decided it removed the legibility too, and the game's reception suffered. The cautionary tale on the shelf above my desk.

Endless Space 2's era quadrants. Four wedges per era, era-gated. A clean compromise between the Civ lattice and parallel tracks. Pretty, legible, and the era gate occasionally forces you to research something you did not want, which is good for the game even when it is annoying for the player.

Every one of these is somebody's favorite. Every one of these is somebody's most hated system. That tells you something about how unsolved the problem is.

Our own scrap heap

The reason I am writing this post is that we have been building prototypes. A lot of prototypes. Most of them did not work. Showing the ones that did not work is more useful than pretending we walked straight to the right answer.

The image at the top of this post is one of them. Here is the rest of the museum.

I am going to include a link to an interactive version of each of these. What looks pretty in a screenshot tends to fail in actual use.

• The Constellation. The picture above. A central node with category-colored hexes branching out across a starfield. Looked like the wallpaper for a sci-fi novel. Stopped being readable somewhere around thirty techs, and we have a lot more techs than thirty. https://www.clairvoyanceai.com/view/share/OLWNMjbf9bpL

• The Radial. Circular layout, techs arranged around the rim. Easier to scan than the constellation. Harder to see how techs related to each other.

• The Web. Free-form graph, nodes wired by relationship rather than tier. The most expressive of the prototypes and the most chaotic to look at. Felt like the Beyond Earth lesson coming back around. https://www.clairvoyanceai.com/view/share/KQvwmm1DmS8X

• The 3D Circuit. A stylized circuit board in three dimensions. I personally pushed for this one longer than I should have. It looked great in stills and was a nightmare to use. https://www.clairvoyanceai.com/view/share/e0N6XCPZ7Inf

• The Organized Table. Rows and columns, no graph at all. The boring one. The one we had the hardest time arguing against on legibility grounds, because it was always the easiest to read. The argument against it is the argument against any pure list view: it is legible the way a spreadsheet is legible, which is not the kind of legible we want. https://www.clairvoyanceai.com/view/share/HK20lSPF7eZT

• The Hex Grid. A flat hex map of techs as tiles, with adjacency standing in for prerequisite. Felt promising for about a week. https://www.clairvoyanceai.com/view/share/aPRde_wgjEsP

There were others that did not survive long enough to make this list. The six above are the ones we sat with for at least a couple of weeks each.

The lesson, after a long stretch of this, is one I should have learned faster. The visualization is downstream of the structural decision. If the underlying structure is a directed graph with several hundred nodes, no amount of art direction makes it feel small. The most expressive layout for forty techs becomes unreadable at eighty and unusable at one twenty. You can hide complexity behind zoom and filtering, but hiding complexity is not the same thing as designing for it.

The reason GalCiv has tended toward parallel tracks for twenty-plus years is not that we lacked imagination. It is that parallel tracks scale. The reason every Civilization ships with the lattice is the same reason. The reason Beyond Earth's web is the cautionary tale is that they tried to escape this and the math caught up to them.

Redo, or refine

Which brings us back to the question we are sitting with for 4.0. Do we replace the existing tech tree, or do we focus on making the one we have do its job better?

The argument for replacing it is the constellation, the radial, the web, the circuit, the table, the hex. We built six prototypes for a reason. The current tree has the four-little-linear-trees problem I mentioned earlier, and dressing that up does not make it go away.

The argument for refining it is the lesson from the scrap heap. Every fancy visualization fell down at scale. The current tree, whatever its faults, scales to the size of game we ship. The risk of throwing it out and replacing it with something prettier is that we end up with our own Beyond Earth web.

Right now I lean toward refine, with one specific structural change I have been chewing on that might do most of the work without us starting over. I am not going to commit to that here, because we are still arguing about it. If we land on something I am sure of, that will be its own dev journal.

My top complaint is that I can’t have a tech have multiple prerequisites. It’s just virtually impossible to do that and make it work in a decent UI of any size.

In the meantime, I wanted to put the failed attempts on the table. Some of them are pretty even when they did not work, and the road to the right answer goes through showing the wrong ones honestly.

If you can think of a tech tree in any game that has over 200 techs (or skills or whatever) that you liked, please leave it in the comments below.

-Brad