How partnership helped Subway Surfers hit 3B

As one of the most successful games on the market, the huge volume of Subway Surfers user-experience data is extraordinarily valuable to Unity engineers. A typical example: When developers found a recurring rendering issue, SYBO passed their crash logs to Unity. Recognizing an obscure engine bug, Unity quickly developed and distributed a patch.

The SYBO team has consistently shared its development work with Unity Copenhagen and Unity tech support, and they’ve contributed as one of the first users of both Nested Prefabs and the Unity Data-Oriented Technology Stack (DOTS). Mathias says, “We’ve been able to challenge the tool and bring out its best. In turn, there have been thousands of hours, hundreds of updates and millions of lines of code that wouldn’t be possible without Unity.’’

SYBO animators take great pride in their ability to make characters feel alive. To enable them to create a cartoony style and energy, the engineers and technical artists came up with custom tooling in Maya and Unity to support this squash-and-stretch feel. “One of Unity’s greatest strengths is how friendly it is for customization, letting developers integrate their own tools,” says technical director Murari Vasudevan.

Custom workflows and content tooling contributed a lot to the Subway Surfers look and feel, and SYBO developed their custom rigging framework in Maya. It let animators quickly and easily set up and reuse advanced rigs and manipulate them.

One of the keys to Subway Surfers’s success is the unique sophistication of its deceptively simple gameplay controls. SYBO can balance the game’s overall difficulty by tweaking how the levels are generated, how big or small the colliders on each obstacle are, and how quickly a user input is detected as a swipe to change lanes. The game can then respond to swiping and move the character in the underlying game logic even before a movement animation has visually finished playing.

“Good players anticipate moves like switching lanes faster than they could visually react,” explains Murari. That’s why SYBO constantly iterates its control mechanisms with feedback from expert players to ensure that the feel is perfect.

Succeeding as one of the world’s most downloaded games requires top runtime performance on a wide range of Android and iOS devices. To ensure good gameplay on even the least-powerful smartphones, SYBO engineers devised a number of techniques, including:

• Batching level geometry to reduce draw calls
• Rotating coins using C# scripts running on the CPU rather than shaders running on the GPU to further minimize draw calls
• Minimizing UI redraws
• Ensuring optimal timing in level generation and not generating more content than a user can see

Murari adds, “the Unity Profiler and Frame Debugger make it much simpler to monitor exactly how all these techniques are working.” SYBO also uses Unity’s different quality settings to optimize FPS and refresh rates on low-end devices.

Subway Surfers displays over a billion ad impressions per month, but they work very diligently to make sure that the ads have a minimal impact on the overall player experience. They try to keep a light touch and have learned, through experimentation, that less is more.

Unity Ads and Unity In-App Purchases (IAP) have become integral parts of SYBO’s overall monetization strategy. What’s important for SYBO is that every monetization experience runs smoothly across all supported devices without affecting gameplay.

Initially, SYBO found that a lot of ads were caching right when the game loaded. This meant various background I/O and networking operations were affecting performance on low-end mobile devices. Working directly with the Unity Ads team, they devised a way to control caching and eliminate the issue.

Rapid, reliable refreshes of characters and settings, while often key to a game’s popularity, can be huge scaling challenges for a fast-growing staff. SYBO is now much better positioned to meet its three-week update cycles and on-demand content needs by switching from asset bundles to the Unity Addressable Asset System, simplifying content pack creation and deployment. This system disengages where assets are referenced from how they’re deployed.

Murari says, “with Unity Addressables, we balance what content is downloaded with the game with what’s downloaded on the fly, keeping the experience as fast as possible.”

SYBO also leveraged the data-driven Unity Editor. “Everything in the game is configurable by scriptable objects added, so designers can do their job without waiting for programmers,” Murari continues. “We can also hook up variables, events and listeners through data binding, which makes the game highly configurable and changeable.”

SYBO’s feedback as one of the first users of the Addressable Asset System and DOTS is but another example of how mutually beneficial the reciprocity between the companies has been.

As SYBO celebrates the tenth anniversary of Subway Surfers, they, along with Unity, look to the next decade of innovation. Both companies are immensely appreciative of their close and exploratory bond. The feedback that Unity receives from developers provides important learnings that help it improve its tools, democratize game development, and build a world with more creators in it.

As a long-term partner, SYBO has been instrumental and has supplied Unity with valuable data to strengthen the engine. Echoing that sentiment, Mathias says, “Our partnership has enabled us to jump on the new technology train faster, allowing us to quickly explore tools that are enabled through the platform. Unity has been instrumental in Subway Surfers reaching three billion downloads, without a doubt.”