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SouthPAW masters the rogue-lite genre with powerful 2D tools
Mar 9, 2022
Game art illustration of Skul: The Hero Slayer

How Skul: The Hero Slayer’s acclaimed pixel art adventure took shape

The challenge
Creating a rogue-lite game experience quickly and cost-effectively using out-of-the-box Unity 2D capabilities.
MacOS, Nintendo Switch™, PC, PlayStation 4, Xbox One, Xbox Series X|S Nintendo Switch is a registered trademark of Nintendo.
Project staff
Game director plus four programmers, two background artists, and one character artist.
Gwangju, South Korea

SouthPAW Games: A Unity case study

How do you make a 2D platformer stand out among hundreds of new titles that go to market every day? What does it take to capture the essence of rogue and create a unique gameplay experience that one reviewer calls “polished to a mirror sheen?” SouthPAW Games turned to the Unity 2D engine and tools like the Tilemap Editor, Pixel Perfect camera, Sprite Atlas, and more to help make Skul: The Hero Slayer an award-winning hit.

Two game characters sitting on a building ledge

Saving time to focus on a better player experience

For small indies like SouthPAW, cranking out great ideas is the easy part. But cranking out game features, with bulletproof code, quickly enough to compete? A little help from the development platform makes a big difference. The Unity 2D game engine’s comprehensive industry-leading tools saved SouthPAW a huge amount of time – freeing up their energy to focus on creating a better player experience.

Skul’s headless body facing his bodiless head

The results

• Creating Tilemaps visually and intuitively in the 2D Tilemap Editor saved hundreds of hours of work.

• Performance gains using Tilemaps and Sprite Atlas made optimization a non-issue.

• Extending the Unity Editor enabled custom tools and extensions to let artists iterate without involving programmers.

• Loading assets with the Aseprite and PyxelEdit Animation Importer saved 200 hours in one month alone.

• Applying the Unity 2D Pixel Perfect Camera component kept pixel art crisp and clear at different resolutions, as well as stable in motion.

“We decided to try the Unity Tilemap editor, and it saved us hundreds of hours of work.”
Skul and a slain enemy holding a sword

Bringing bones to life

Like many small indie studios, SouthPAW Games was started by a group of friends learning game development at university. Now-CEO Park Sang-woo, primarily a designer and animator, put the team together in 2017 to start work on a 2D, pixel-art rogue-lite platformer that would extend the tradition of Kirby and MegaMan.

The project evolved to become Skul: The Hero Slayer, which follows a small skeleton who transforms into an array of different characters by changing his skull. To rescue his demon king, he fights adventurers and an imperial army with fast, precise, and varied gameplay. The title has won numerous honors, including Best Indie Game in the 2020 Korea Game Awards and Best Innovation in the 2020 Made with Unity (MWU) Korea Awards.

A Skul game boss holding a huge sword

Getting physical with pixel art

Unity 2D Physics played an important role in making the Skul hack-and-slash action effects feel authentic. Armor and weapons go flying, and SouthPAW created rotational effects on the objects by producing a sprite for each rotation angle. The effects were impressive, but they needed to use them judiciously. “The visual impact is amazing, but the cost is significant, so we only used it for the most important sequences,” says Sang-woo. One technique to minimize these costs without directly impacting gameplay was lowering the 2D physics accuracy setting. And when the game needed higher accuracy for player movements, they often used scripts with functions such as physics2D.raycast and collider2D.cast.

A constant challenge with pixel art is ensuring that asset resolution is consistent throughout the game. Fortunately, SouthPAW anticipated the issue in preproduction. Sang-woo recalls, “The reference resolution of our existing assets was too high, the graphics were unnecessarily detailed.” After recreating the visual resources for a pixels-per-unit (PPU) of 32 with a Tilemap grid of 32x32 pixels per tile, they used Game view and tested their output on PCs to check for graphic sharpness at different resolutions.

Leveling up with the 2D Tilemap Editor

The 2D Tilemap Editor package was a key Unitycomponent for designing and building Skul levels. Sang-woo had developed his own custom map editor for a previous 2D game, but it took considerable effort.

“We decided to try the Unity Tilemap Editor with Skul, and it saved us hundreds of hours of work,” says Sang-woo. “It was a built-in Unity component, and we could see how it worked right in the Editor.” The Tilemap Editor let developers create maps visually and intuitively while maintaining full control with the API.

SouthPAW created three types of Tilemap – Terrain, Terrain Foothold, and Platform – with different collider parameters. “We optimized Colliders by binding the Tilemap Collider 2D into a single Polygon Collider 2D,” Sang-woo explains. The team also created a script to classify and set the tile type by inheriting the tile class.

Skul The Hero Slayer open in the Unity Editor

Extending the Editor

Extending the Editor let SouthPAW integrate many of their own custom tools. APIs for the 2D tools allowed the team to create extensions that let artists iterate different options without needing to involve programmers for code changes. Another huge time saver was the Editor’s seamless integration with the Aseprite and PyxelEdit Animation Importer. According to Song Jihun, a programmer at SouthPAW, “We just dragged the resource files into the Editor window, and they were automatically converted into animation clips and controllers.” If the designer modified a resource, a new import automatically updated the animation file. “We saved about 200 hours in one month alone.”

Drawing from a comprehensive toolkit

For SouthPAW, having all the 2D tools they need integrated within a single development platform is a huge asset. Jihun says, “The way Unity seamlessly integrates all its capabilities means we spend much less time testing and spend more time on quality.”

For example:

  • SouthPAW used Sprite Atlas, which packs together sprites present in the same map to optimize draw calls and memory consumption.
  • The studio maximized their game’s reach on low-end devices by editing scripts in the Universal Render Pipeline (URP).
  • Presets and the Preset Manager enabled greater consistency when creating newSkul items and characters.
  • The team kept Skul pixel art crisp and clear at different resolutions and stable in motion by using the Unity 2D Pixel Perfect Camera component.

The team also said that they plan to make greater use of the Shader Graph in their next effort. “We understand cameras, rendering, and shaders, but with the Unity component, we don’t need to be experts to get the best results.”

Promising a great experience

SouthPAW took advantage of the Unity Indie Clinic Program, a Unity Korea service, to learn a number of optimization techniques, as well as the basics of profiling to find CPU bottlenecks. It paid off with first prize when they premiered Skul in the Unity Global Indie Game Development Contest (GIGDC).

For its next game, SouthPAW looks forward to using some Unity 2D tools that were released in the middle of their Skul sprint. Jihun says, “We used the Unity 2D Animation package – Unity’s 2D skeletal animation solution – for another small project, and because it’s optimized for the Burst compiler and the Unity Job System, the performance was amazing.” They’re also excited about applying 2D Sprite Shape and 2D Lights. And as elated as they were about officially releasing across all its target platforms, SouthPAW sees this as just a checkpoint on their Skul journey. Sang-woo insists, “We’re going to keep listening to our players and keep updating the game until they get the best Skul experience they could ever imagine.”

Game art illustration of Skul The Hero Slayer

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