League of Legends: The art of balance

Competitive titles like League of Legends can live or die on how well balanced they are. With League in particular, there is a vast gulf in player skill, from the lowest ranks of Iron IV to the peaks of professional play, and each segment needs to be considered to ensure the game's continued success.

Developed by Riot Games, League of Legends is one of the most popular games in the world, boasting over 100 million monthly active users. Last year, the World Championship final attracted a peak audience of 44 million, and the game generally peaks at eight million concurrent users everyday. But it's a game with a long history and a lot of baggage: with 148 playable champions, hundreds of in-game items, and countless team compositions, balancing League of Legends is a delicate process.

As John Frank, game design manager of the Summoner's Rift team tells GamesIndustry.biz, balancing an "endless attempt at perfection" with the recognition that "we'll never get there."

Small stat tweaks, new champions and overhauled older ones, along with new items, monsters, and even minor alterations to the map can change the game substantially. One week tanks are dominant, while the next week it's assassins or burst mages. Like most competitive games, League is a game of small margins. Just a few percentage points one way or another can lead to dominance or underperformance within the game. When it comes to balance, Frank says it's done "very carefully."

"Our team has built up a lot of experience when measuring and analyzing what impact a set of small stat changes can do. League is delicate when you consider how easy it is for a champion to get out of line, but it's also more resilient on the systems side so we've been fortunate in that respect that the core game carries a ton of weight as an enjoyable experience on its own."

League is a game of constantly shifting metas, sparking chain reactions from one update to the next. There is an almost cyclical nature to the game, as certain strategies fall in and out of favour among regular players and pros alike.

"We rarely say things like, 'We want tanks to be dominant.' But we will notice when a class or group of champions are weak or underserved by existing systems and will look to correct that. Sometimes we'll overcorrect and it takes a while for the meta to shift so we don't know immediately if we've gone too far."

"League is delicate when you consider how easy it is for a champion to get out of line, but it's also more resilient on the systems side"

Where possible, the balance team uses a data-driven approach to help decide when something like a champion or item needs changing. But there are other changes which can't be so easily boiled down to raw numbers.

Take for instance the recent introduction of small alcoves to two of the game's three lanes, or how the map can physically change based on how the game plays out; for nearly ten years, Summoner's Rift remained largely unaltered, save for the odd new bush here and there -- but the impact of these changes to the most central and consistent aspect of the game are not so easily quantified.

"For more abstract changes, we try to understand what goal it is that we're trying to accomplish with them during the development phase," says Frank. "As an example, the recent addition of alcoves were added with the intent to encourage occasional highlight plays.

"We didn't want to completely throw lanes and the play patterns in them into a state of flux, but were hopeful that they'd add player satisfaction in the moments where players are able to utilise them in a flashy way. We were able to prove that internally through playtests and fortunately, player experience -- measured through sentiment data -- has matched those expectations."

In order to meet those expectations and ensure the game doesn't become unrecognisable to its audience after years and years of changes, the balance team employs "a lot of people who love League as a game."

"So we tend to have a high amount of respect for the product and have little interest in table flipping it," says Frank. "We also have a crew of highly engaged, elite players that constantly give us feedback if they think we're going too far. We hit a period where we were clearly making too many changes and causing pain for players so since then -- this was a few years back -- we've aimed for more deliberate change with less re-learning for the average player."

"While I agree that we haven't hit critical mass, we're at a point where we are actively reflecting on clarity and simplicity of our projects"

Looking at League of Legends today versus ten years ago, it's still the same game despite having changed so much. Most notable is the evolution of mechanical complexity over that period; older, more simple champions have been extensively reworked to add new layers of depth, but with this comes the inevitable utility creep. Over-engineering new champions or systems runs the risk of altering the game, as it reaches a critical mass of complexity. This is an issue the balance team has had to accommodate, especially as League's tail grows longer and longer.

"In the recent past, we may have been too focused on depth being the mark of a good champion without recognising the cost of additional complexity," says Frank. "With an eye towards the future, we want to consider the complexity cost, and get the additional depth only where the gains merit it.

"While I agree that we haven't hit critical mass, we're at a point where we are actively reflecting on clarity and simplicity of our projects. But at the end of the day, we want to deliver to players what they love so if they want deeper champions and mechanics, we'll do that. But if they want doses of simpler champions in-between, we'll be sure to service those players too."

As League of Legends lead designer Greg Street told GamesIndustry.biz back in January, the key strength of League is that "it's difficult to learn, and impossible to master."

"There is always something new to learn, you can always get better and we believe that the process of learning something and seeing yourself improve is just satisfying on a very human level," Street said.

This is a sentiment echoed by Frank.

"We're devoted to getting better because we want those hours people have spent training in Summoner's Rift to matter and their passion to be justified by a well-balanced game. It's ultimately the players that make Summoner's Rift an amazing competitive experience.

"We've also done a lot of work over the past couple of years to be more visible and transparent with our players about our balancing principles, so we'd like to encourage them to check out our Champion Balance Framework for more specifics. We're looking to do something similar with our other processes too for things like systems and item changes in the near future."