Using a modular system of maneuvers to design Psychonauts 2's boss fights in a hurry

At her GDC 2023 talk today on AI and boss fight design, Double Fine gameplay programmer Rebecca Vessal showed off her team's modular approach to designing and implementing larger-than-life encounters in a rapid timeframe.

After looking at the nasty mess of dependencies for animation and traditional blueprints (Unreal Engine's visual scripting system) that can occur when developing boss encounters, Vessal and the team came up with a system they called "Maneuvers," which allowed the animators, designers, and programmers to work closely together without messing up file dependencies or creating bottlenecks for one another. A modular system that uses data (here defined as a set of variables that animators and designers can tweak, in a relatively simple interface) to produce a desired action, Maneuvers allowed the team to build out and iterate on bosses in the allotted time.

Three of the game's iconic bosses were on display to show off the Maneuvers system: Lucky (aka Lucktopus), Cassie (aka the Die-brarian), and Maligula, all of whom had bespoke animations, behaviors, and dialogue but benefitted from using the modular system to share some basic elements.

Rapid prototyping for boss battles

"As you can see here, we actually didn't really have that much time to work on the bosses and they were actually made in late production with a very small team, and we needed to be able to pivot very quickly to make the boss fights really fun," said Vessal, pointing to a slide that showed the production schedule they were working with.

"We were trying to figure out basically the different systems that we were going to use for boss fights... as you can see here Lucky boss and Maligula boss only got two months for concepting and prototyping. And then we didn't really have too much time afterwards because we were very close to shipping."

Using the system, the teams were able to repurpose attacks (such as projectile or melee attacks), tweaking all the variables as needed for the boss in question, and even for the specific phase of the boss. The system was lightweight enough to allow for dialogue to be plugged in at appropriate times, and for some light randomization in terms of attack patterns (within the accepted parameters), which all followed a pattern of telegraph, attack, and recovery, all of which could have chains and sub-chains of behavior and animations.

"The great thing about this kind of setup too is that it's very easy for animators to figure out the animation sequences that correspond to these attack sequences," she said.

"And they can easily drill down into each [action] and swap out different animation sequences if they need to. So when it comes to crafting an attack sequence, it's very easy, actually, you simply just have to create the maneuver chain... it's very easy to add or remove whatever maneuvers you wanted to happen for that attack sequence."

She ended on a Raz-approved slide advocating for the overall approach, and noted that this system could work for more general purposes and general boss fights, for devs who want to enjoy the benefits of their own maneuvers.