Building Better Skill Trees

These days, it feels like you can’t release a big blockbuster action game without one of these things: a skill tree. You’ve definitely seen them before, in games like Tomb Raider and Watch Dogs. They often have three distinct branches, with cute names like innovator or hunter. In these games, you accrue experience points by playing through missions, and whenever you hit some sort of arbitrary threshold you get a skill point.

A skill point, which you can spend to unlock a new ability. This might be something funky like a brand new move, or something a little less exciting like a few extra health points. Skill trees like this were first found in number crunching RPGs like Diablo 2, but have since become ubiquitous in big budget action games - in everything from Spider-Man to DOOM, to the point where it’s now just an expected part of a modern console game, like climbable towers, and microtransactions.

But while I find a lot of these tropes to be pretty cliched and tiresome, I can totally see why skill trees work, and how they can benefit certain games. For one, they can be used to trickle out complexity over the course of the game. If you started God of War with all of Kratos’s powers, it might be completely overwhelming and some players might stick to the simple stuff and never delve into the finer details of the combat system.

But when you earn new powers from a skill tree, your mechanical move set opens up incrementally over the course of the game. And because you spent some kind of currency on that move, you’ll probably feel compelled to actually use it. Skill trees are also a nice way to make players feel like they’ve grown in power over the course of the game. At the start of the adventure you’re weak and have only a few special powers - but by the end you’re a walking tank with armfuls of abilities.

This also can be used to keep players engaged. They can scan the skill tree to get a preview of abilities they’ll be wielding later in the game, and then stick with it until they get to to that point, excited about the prospect of playing with all those new powers. Skill trees also add meta level decision making into a game. They can create a different experience each time you play. And they give the UI team something to do.

Someone’s go to draw all those icons. But for all their benefits, most games squander their skill trees by making really poor choices about what to put on those branches. And so in this video we’re going to talk about some popular mistakes that skill trees make - and how we might be able to fix them. For starters, a lot of games that feature skill trees will allow the player to unlock most of the upgrades, if not all of them, by the end of the game.

Just through a normal amount of play. And this really misses an opportunity to make players think hard about their choices. They’re only thinking about what order they unlock the skills - when they could be thinking about which upgrades they’re actually be able to get. I personally enjoyed the skill tree in Assassin’s Creed Origins, because I definitely wasn’t able to afford all of the skills by the end of the game. Instead, I had to specialise - I focused on the hunter and seer branches, which were all about improving my abilities in stealth, and increasing my options in taking out camps through tricking the AI and causing chaos.

This created some cool outcomes: like how the Bayek in my game felt personal to me and his skills fit the way I chose to play the game. But there were also interesting repercussions for my choices: by neglecting the warrior branch, i was pretty lacklustre at one-on-one combat. I often had to run away from direct encounters and find new ways to approach situations. Immersive sims are also good at showing the repercussions of picking certain skills.

In the Deus Ex games, certain paths and options will be locked out based on the upgrades you’ve chosen, forcing you to find alternate routes that better suit your character. And in Prey, the more skills you unlock, the more alien you become - right up to the point where friendly turrets now consider you a threat and try to kill you. Another way skill trees screw up is simply by making the skills just really boring. Making your attacks do a few percentage points more damage, or giving yourself a couple extra health points… is just not very exciting.

So brand new powers in Dishonored and exciting new attacks in God of War are far more desirable than a few extra numbers on the game’s underlying Excel spreadsheet. And don’t forget the rules laid down in Metroid: one ability can serve multiple purposes, like the ice beam, which is both a weapon and a way to navigate the world. Ultimately, a good skill will make you excited to finally unlock it, and then eager to go into the world and use it.

Back to Origins for a second, I find myself caught in a really engaging loop where I’d unlock new abilities - excitedly test them out on a few camps and missions. which gave me enough experience points for another ability… and so on. That being said, skill trees should generally avoid mechanics that the player should already have by default. When i played Horizon Zero Dawn, I was peeved that I couldn’t grab enemies from ledges like every other game of its ilk - until I found out it was an unlock-able skill.

Same goes for Mirror’s Edge Catalyst, which locked Faith’s leg tuck move behind an upgrade menu, despite it being accessible from the start in the first game. Oh, and don’t feel the need to add in crappy skills just to boost the numbers. Some skill tree designers obviously believe that bigger is better - check out these monster skill forests for Path of Exile and Salt and Sanctuary - but if you ask me, a tightly pruned bush with a handful of truly interesting upgrades is often the best solution.

Another issue plaguing skill trees is the actual process of earning these skill points. Most games give you the points simply for playing the game normally, which feels like a missed opportunity. Let’s go back to Prey, which has these Neuromod tools (the game’s version of skill points) as physical objects in the world. This means you have to go out there and find them - maybe by exploring the different nooks and crannies of Talos 1, or by doing side quests.

Choosing how to dole out these skill points allows the designer to encourage a certain play style, or to make players check out optional content. Like in Zelda Breath of the Wild, where Spirit Orbs, which can be cashed in for health and stamina upgrades, are given for completing these shrines. That essentially turns the entire world of Hyrule into one giant skill tree. This also makes players actively work towards improving their character, rather than randomly getting stat boosts as they play.

This reminds me of Far Cry 3’s crafting system. in that game, I knew I wanted a better gun holster - and the menu told me that I needed to get a few pelts from a certain animal. So I paused the main quest, found the animal’s breeding ground on my map, and went hunting for pelts until I had enough to afford the holster. I wanted an upgrade and had to figure out how to get it, and had to actually work towards that goal.

Getting the, uh, sprint slide, though? Well, I just played the game a bit more until I got given some skill points. Look: you don’t really need to encourage the player to simply play through the main missions - that’s why they bought the game in the first place. So use the promise of skill points to encourage other ways to play. To play skilfully, or play on harder difficulties, or explore more, and so on. But be careful about exactly the sort of gameplay you encourage.

Skyrim’s system, where players get skill points for performing certain actions, can persuade players to just craft dozens of daggers, simply to boost their crafting skill. You don’t want to encourage grinding, or gameplay that doesn’t fit the core experience. One final issue is that these skill menus are pretty boring to navigate. They take you out of the game world, and into a menu screen that looks like you’re buying travel insurance or something.

This is not a huge deal in an expansive adventure like The Witcher, but it can massively slow the pace of a lighting quick game like Doom. So just make them quicker. Like in Downwell, where it flashes up three upgrade choices between levels. You pick one, and away you go. Or just make them automatic. Red Dead Redemption 2 has skill trees for both Arthur and his horse, and these upgrades - for things like boosted stamina and sweet horse tricks - just unlock as you play.

Though, whether Doom even needed skill trees in the first place, is another question entirely. The thing about skill trees is: there’s loads of fun stuff you can do with them. How about skills that offer both advantages and disadvantages to the player? Or skills that can interlink in various ways? Or skills where you can only equip a handful at a time? Skill trees feel like one of those systems that’s in every game nowadays - simply because they’re in every game nowadays.

But that doesn’t make them bad - it’s just very easy to get a bit lazy with them, and do what everyone else is doing, regardless of whether it suits the game, the experience, the pace, and so on. So get creative with them! A skill tree isn’t about making the player wait half the game to get all the mechanics they should have at the start. Or going into a boring menu to get a boring health boost. They’re about customising your experience.

About rewarding different ways of playing. And about forcing difficult choices. Lemme know about your favourite skill trees in the comments below, and I eagerly await a million comments about this crazy Sphere Grid nonsense from Final Fantasy X. I have no idea what this thing is…