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SAN FRANCISCO — It’s not easy making changes and tweaks to the most popular game in the world, and its lead designer says it’s painful when he and his team do something wrong.

League of Legends has millions of active players who obsess over its every little detail, and this puts a lot of pressure on developer Riot Games to get things right. In a panel today at the Game Developers Conference 2015, lead designer Ryan Scott admits that Riot makes mistakes. And when a developer does something unpopular with a game the size of League of Legends — well, they hear about it.

That’s something Riot knows to expect — and not just because of how many people play and enjoy League of Legends (a game that was on track to make more than $1 billion last year) but also because it’s so deep that every change can have a ripple effect across how the community plays. But it’s that depth that Scott is always going for.

“Depth is something I feel very strongly about,” Scott said during his GDC session. “I think the paradox exists of wanting to make something deep while simultaneously wanting new people to feel they can enjoy it. As an industry, we analyze it in a way that is intuitive, but I don’t think it’s correct.”

He listed off the likes of Counter-Strike, StarCraft, and Halo as examples of games that he believes are still relevant due to their deep mechanics. They all have high levels of mastery, and this was something that Riot set out early on to ensure League of Legends would include as well.

“The real paradox is that if you try to make your game widely appealing first and then try to add complexity on top of that — it won’t work,” said Scott. “Because you’re building on a weak foundation. There’s nothing to hold up the house. Accessibility is great, but it cannot be your foundation.”

Scott elaborated on how his team strives to add fun without making it needlessly inaccessible.

“Complexity and depth have a relationship,” he said. “But they are not the same thing. Complexity is a cost, and you try to add the least amount of cost to get the most depth.”

That ratio guides Riot in most of its design decisions, but complexity versus depth is only one part of the ratio. Scott also notes that his team is always trying to keep fun in mind as well. But depth and fun are not always natural allies, and when people are having a good time with something that is simple or dumb, it’s hard to take that away from them in the name of increasing League of Legend’s depth.

“There’s a lot of character skills that we created that actually limit choice, and that’s where we failed,” said Scott. “But they are fun. The hardest thing that is pushing up against depth is fun. That’s what presents us with judgment calls that we often fall on the wrong side of.”