Game Design Deep Dive: The plant-growing mechanics of Ubisoft's Grow Home

With big-budget titles like Watch Dogs and The Crew under his belt, designer Andrew Willans of Ubisoft Reflections dives deep into the design of the vertically-astute PC game Grow Home.

Game Design Deep Dive is an ongoing Gamasutra series with the goal of shedding light on specific design features or mechanics within a video game, in order to show how seemingly simple, fundamental design decisions aren't really that simple at all.

Check out earlier installments on the tutorial system in 
Rogue Legacy and the rhythm mechanics at work in Crypt of the NecroDancer. 

Also don't miss these developer-minded looks at the movement system in Road Not Taken and Amnesia's "sanity meter" from earlier in our ever-growing Deep Dive archive.

Who: Andrew Willans, senior game designer at Reflections, a Ubisoft studio

My passions include snowboarding, shock cinema and VR…now just imagine those in a game generating blender! Previous titles include: Driver San Francisco, Watch_Dogs, The Crew.

What: Star Shoot Mechanic in Grow Home

The Star Shoot mechanic refers to the growing (and riding) of the Star Plant in Grow Home.

Grow Home is an open-world, third-person adventure which uses procedural animation to power the movements of the avatar and offer an unbounded climbing experience. The main objective in Grow Home is to grow the giant alien Star Plant to 2000 meters. At this height, the plant will flower and produce seeds which can be collected and sent back to our hero’s home planet for propagation.

The Star Shoot mechanic is used to connect the Star Plant to Energy Rocks. These rocks contain nutrients that are automatically absorbed by the plant once a connection is made. With every Energy Rock connected the plant will grow in size by a predetermined amount. Think of these Star Shoots as being like the roots of a plant. When the shoots absorb the nutrients, the trunk (or stem) of the plant grows. As the trunk grows higher, it connects a series of large floating islands that can be explored as players progress on their vertical journey.

Star Shoots connect Star Plants and Energy Rocks

Locating and connecting the plant to these nutrient sources is a core gameplay objective, so obviously it needed to be fun, and repeatable. The evolution of this plant growing mechanic radically changed during our short development cycle. These changes affected the minute-to-minute gameplay, the level design of the entire map, and the high-level game progression. To fully appreciate the impact of these changes, it’s important to understand the evolution of our toy box.

Procedural animation was a core pillar for our game. The climbing mechanic it fuelled was our breakthrough feature. It allowed the user to climb on any surface, from any angle, and to experiment with weight transfer and stretching between two independent grab points. Not only did it feel intuitive, but it also had depth. This was confirmed in internal playtests which recorded radically different best times from the same climbing wall.

To make a game that focused solely on climbing through a level-designed environment seemed like an obvious choice, but our tiny team size simply couldn’t support this from a production perspective. So we looked for ways to put more ownership on the player. If the player could create their own climbing walls as part of a larger environment then we could potentially deliver the mountain-sized experience we were aiming for.

The Star Plant started life as a small plant that could be grown in a player-specified direction. This “beanstalk,” as we called it during development, grew in an “approximate” direction. The direction was controlled by grabbing and rotating a “growth bud,” and then pressing an input to initiate the plant growth. The duration of the growth, and the extent to which it curled and twisted, appeared very random at times. This lack of predictability added to its organic charm, but was also provided some frustrating moments when trying to aim in the direction of anything specific.

This lack of precision was fine in the prototype phase. In a large open world without obstacles, the mechanic worked reasonably well, but once we started to add items of interest we started overshooting objectives, or falling short of them and having to grow additional sections to bridge the gaps. These items of interest were the floating islands and climbable structures that were an essential part of the design. They helped to define the flow, pace, and variety of both gameplay and game ingredients. The islands contained collectible crystals that unlocked avatar perks, they contained climbing puzzles that scaled in difficulty with the placement of crumbling rocks, water currents, hazardous plants, caves and tunnels. We wanted players to visit these locations. They were essential to game progression and the narrative, but we needed to make this part of the journey easier and a lot more enjoyable.

The second issue which fed into the redesign of the growth mechanic was related to climbing fatigue. When the plant grew the new sections of growth appeared in front of the player. The player’s avatar remained gripped to the point where they initiated the growth, observed as the new sections grew, then climbed the new sections to gain attitude and start the cycle again. There was no break in the climbing gameplay until the player reached an island or grew a leaf to use as a resting platform. We were in danger of making a game that was 90 percent climbing. Even a velvet-covered gamepad couldn’t have eased that test of finger endurance.

We decided to move the avatar's grip position to the front of the plant section. As the section grew they remained ahead of the new growth. This was the first step, and it resolved some of the climbing fatigue issues relating to the plant. However, the lack of control was still a concern, mostly because the organic-looking twists and turns frequently left players dangling upside down when the plant stopped growing. We tried applying after-touch inputs to control the direction of the growth once it was in motion, but these were a mixed success due to excessive demand they placed on the player to constantly manipulate the game camera.

To finally resolve the accuracy issue we had to give the player complete control over the plant. They had to literally fly it. The mechanic was then lovingly referred to as "riding the dragon," a fantastic reference to the Falkor flight sequence from the film The Neverending Story. The mechanic allowed players to reach their objective with more intuitive control, and also have fun on the journey. We still added a small amount of resistance to the controls. This was to try and ensure the grown sections were not in a perfectly straight line, looking totally unnatural and at odds with the rest of the world. We also allowed the sections to continue growing if, for any reason, the player let go. In these instances the plant sections would finish their growth cycle by making curves and corkscrew shapes in the general direction they were pointing when released.

We had succeeded in creating a more fun growing mechanic with far fewer frustrations, but in doing so we ran the risk of making things a little too easy and impacting the sense of achievement from progression.

The concept of roots or branches feeding and growing a central trunk was something born of this need to control the level of challenge. Initially, all the parts of the plant were considered as a whole. Each section provided growth buds to create newer sections. Using this version of the mechanic, players could gain height almost indefinitely -- they simply needed to keep growing higher and higher. We experimented with an economy system based around the plant. To grow a branch, a player needed to collect and spend a unit of “pollen.” Pollen-producing flowers grew on the plant and part of the gameplay involved locating and collecting pollen (and even dodging the attacks of some giant alien bee creatures at one stage).

The economy system worked, but it also felt a little artificial and over-designed. It was an obvious feature to include, clearly there to support a game loop that didn’t particularly excite. It was additional busy work used to buy time with a fun mechanic, so we cut it. This is a one of the creative benefits of working in a small team -- we can agree things quickly, change a feature within hours, and properly evaluate the effect it has on the game as a whole.

The initial blueprint for the game had included three Star Plants and three major climbs. At the top of each climb was a larger floating island. These large islands were there to introduce more horizontal gameplay (jumping, platforming, exploration), a much-needed break from the constant climbing. They also rewarded the player with new mechanics in the form of a parachute made from a daisy, and a glider made from a dried out leaf. In typical three-act structure, the player would ascend to their goal, receive their reward, and then use this reward to reach the opening of the next act. It worked, but it was also a very familiar journey, and the improved growing mechanic now made this journey a lot shorter. The Star Plant was in danger of becoming a mode of transport, and not the major character we wanted it to be.

We needed to focus the action back on the Star Plant. It had to be central to the adventure, always present and visible from wherever the player was exploring. The solution was to radically change the purpose of the plant within the narrative, changing everything from the placement of a small floating island to the high level fantasy of the game.

In our first pass of the narrative, an accident had left BUD crash-landed on the alien planet, needing to find a way back to his spaceship which was parked in the orbit of the planet. There was no help coming and the quest became one of escaping the environment by using nature not technology. This essentially meant using the plant to build a bridge to your spaceship. To give the plant more character it needed to be more than just a mode of transport, it had to be the reason why BUD was there in the first place. This inspired a change in the narrative, and gave BUD a new job title. He became a galactic gardener, and his job was to grow and harvest the seeds of a giant alien plant.

Mechanically we also needed to rethink the structure of the plant. The Star Shoots (plant roots) become an almost unlimited mechanic that could be used to meet an objective (connect to Energy Rock), as a mode transport to explore the environment (reach other small floating islands), and even as a tool for artistic expression (creating loops and climbable shapes in the sky). The central trunk of the Star Plant would grow along a predetermined spline and connect the larger floating islands which offered the horizontal gameplay. It was the backbone of the quest, a central climbable pathway between goals, and it had to be grown, because it would eventually flower to produce the very items need to complete the quest, the seeds.

Why did the Shoot Star mechanic turn out this way?

When time and resources are limited, it can force you to find creative solutions. All of the tweaks and tunings we made to the mechanic instinctively felt like improvements. The moment-to-moment gameplay became more enjoyable and less of a grind. This in turn made the plant more valuable, like a special ability that was constantly available.

Almost every design decision was led by the desire to embrace the joy of just playing in the world and having fun. We knew that falling from the plant (or any of the floating structures) was a real threat, but we also had no desire to remove this threat as it was essential to support the drama of taking risks. Recovering from a long fall could be quite punishing, so we had to fill the world will ingredients to either prevent this in some places, limits its impact, or offer a fun way to regain the lost progress. This led to the addition of bouncing leaves on the plant, teleport spawn points, and geyser like alien plants. Increasing or regaining altitude became our primary concern, and anything which assisted this was considered a step in the right direction.


The vertical journey felt like a fresher approach to mapping out a progression. It was more compelling because the floating islands could be seen from directly below, only revealing their splendor once the player has crested them. The glider and parachute mechanics became far more essential. They were a valuable safety net to prevent falling too far, used for exploration and for play. The player had freedom to grow almost anywhere, but the importance of growing the central trunk meant that we could structure when and how new ingredients were introduced.

In refining a single mechanic we had altered the structure of the game. The knock-on effect was radical, but also provided us with a stronger narrative in addition to increasing the comfort and fun of the mechanic we set out to improve. If faced with the same challenge again, I’d be less cautious in embracing the freedom given to the player. As a designer, you instinctively think about how you can structure a game and control the pace and flow of events. The functionality and economy of a mechanic often play a large part in this structure.

Sometimes it’s liberating to stop worrying about the duration of the playtime, and just embrace the joy of playing.


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