How the creators of Rusted Moss came together to create physics-based hook action


Rusted Moss is an action and exploration game created by individuals (not part of any development studio) that relies on an unusual method of movement: a ridiculously springy hook. We won’t lie: physics-based grappling will bring you both great pain and great joy. But it’s a triumph once you get the hang of it – you’ll practically fly through the game blasting enemies with your arsenal of weapons when Rusted Moss arrives on PS5 on June 20.

In this melancholy world, people prepare for an invasion by capricious fairies from another dimension. You play as Fern, a misfit determined to end the war. As you discover the story behind the world, you will finally choose a side: fairy or human?

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With the release of the PS5 version, we will also add seven to eight hours of additional content – roughly the same amount as the base game. This includes up-to-date zones (moderate to very complex), a boss fight, and an additional playable character.

Unique grabbing hook

During a demo with indie developers, Emlise (the lead creator) showed off a hook that worked like a bungee cord or rubber band. She performed amazing, crazy maneuvers that made time-honored platforming skills like double jumps and dashes seem so narrow. I’ve never seen anything like this – hooks in most games just pull you to an anchor point or cradle the player in stationary arcs.

It looked so polished that I was sure he would develop it into a full game. But she had no such plans. She saw it as a programming exercise to learn Verlet integration (the numerical equation used to calculate trajectories).

“Players would find it too difficult. It takes a while to get used to it,” says Emlise.

We then each did our duty as friends and kept the pressure on her to continue to grow. My sister and I also joined her, forming our 3-person development team. It was strange because we had no intention of creating a game together before.

Rusted Moss was created to bring these mechanics to life, not to create a game or become a full-time indie developer (my sister and I work outside the gaming industry during our day jobs).

I think its origins gave purity to the foundation of Rusted Moss because there was no question what kind of game it could become. Everything would revolve around one basic mechanic – grappling hook.

Please stop our game

Synergy with the hook became the main design goal of Rusted Moss. All the skills you learn improve your physics-based movement, whether it’s a charge jump that lets you fall further or a weapon recoil.

This maximizes the player’s ability to express and be innovative. Progression doesn’t rely on a plain lock and key solution, which is a design scheme often found in other action exploration games.

Thanks to these synergistic abilities, we saw the same platforming challenge solved in five different ways. If a player is innovative, determined, and skilled enough, they can “break” our game and show us moves we didn’t even consider when creating Rusted Moss.

During the quality assurance testing period, we took this philosophy to the extreme. One tester found a bug that gave them unintended movement abilities. Instead of fixing this, we added a visual effect when this ability is busy. We love seeing our players discover this “secret skill” in the game.

Extraordinary children

The main character, Fern, has a pointed and sour personality. Women are often pressured to be nice and think about what “nice” means to the people who interact with them. Based on our experiences as an all-female development team, Fern is a power fantasy that defies this narrative, sometimes to the extreme. He speaks his mind, which is often quite nasty and honestly…comical!

This is consistent with her identity as a changeling – a fairy who replaced the stolen child. In folk tales, children who behaved strangely were identified as changelings and treated cruelly. We can now think of them as neurodivergent or unusual in some other way. We wanted to explore topics related to children that turned out to be something parents didn’t want or expect.

Get ready to learn all the tricks Fern has, and you might discover some up-to-date ones when Rusted Moss arrives on PS5 on June 20.

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