The Sonic the Hedgehog franchise has seen an incredibly wide array of gameplay styles, from 2D side-scrolling platformers in its early days, to high-speed reaction-based gameplay in the modern games.  With such a passionate fan base, there’s no shortage of opinion on what works best.  Some prefer the newer boost-style games, others prefer the free-roaming Adventure titles, and others enjoy the heavy momentum-based gameplay of the classics.  What makes each of these types of games engaging, and what is ideal for the future?

At the Digital Dragons conference in 2017, game designer Hirokazu Yasuhara spoke on the nature of fun and play.  In his presentation, Yasuhara-san described a model of how the brain produces “fun” signals, using Roger Caillois’ four categories of games; competition, chance, roleplaying, and vertigo.  The human brain has a natural tendency to detect patterns and spot differences in those patterns.  By tracking changes over time, the brain is able to predict and evaluate information.  Initiated by a sense of desire, the brain predicts an outcome based on its mental model, puts this prediction into practice, and then concentrates on and evaluates the result.  If the result matches the prediction, tension is released and stimulates feelings of fun.  If the result does not match the prediction, the feeling of tension tells the brain to update its mental model.  This engages the brain in the “chance” and “vertigo” aspects of play.  The cycle of creating and relieving tension is the core of a game’s experience.

The platformer genre began with very simple models that were easy to predict.  Characters ran left-and-right and jumped up-and-down.  These are very simple vectors, with the only acceleration coming from gravity.  Eventually platformers would develop more complexity such as the Super Mario Bros.’ accelerated running, but even this model had relatively few variables.

Enter Sonic the Hedgehog, a game that pioneered new forms of momentum in platforming. The physics model of the classic Sonic games was significantly more complex, mimicking the properties of a ball interacting with slopes. Slope angles, relative gravity, and their effect on velocity were part of the core platforming mechanics. Suddenly, running on the ground is no longer a matter of linearly progressing along a surface, but an elaborate interplay of these variables. The effects on momentum from gently rolling hills to sharp curves and changes in direction were a recipe for an engaging game that evoked all four outlined forms of gameplay, especially vertigo.

Since transitioning into 3D, Sonic has struggled to evoke the same feelings as the classic games did.  Early on, the Adventure games attempted to stick to the principles of the 2D games, and did relatively well at preserving the flow of gameplay despite the challenges inherent to 3D programming.

Due to various hurdles afterward, Adventure-style gameplay was eventually dropped and more focus was placed on Sonic’s speed with a new boost-style gameplay.  Sonic was given the ability to boost to top speed, and the gameplay was based more on the player’s reflexes.  Many players enjoyed the sense of speed this new boost model provided, but there have also been complaints about the depth of these mechanics.  Because these games eliminate momentum from the equation, things like acceleration, slope angles and gravity make no tangible difference to the physics model.  While boost gameplay provides a great sense of vertigo, the building and release of tension is often too unpredictable, and may cause some players to feel frustrated or disengaged from the experience.  Critics of this gameplay style often say, “Speed should be earned, not given.” This touches on a valid point, but misses some important details.

For those who seek a deeper gameplay experience, the fun of a Sonic game does not lie in the speed alone.  It lies in the in-betweens of momentum; the acceleration.  When variables such as acceleration, gravity, slopes, pressure and friction all work in tandem and predictably with each other, the experience has multiple points of tension and release and can be far more engaging as a result.  A model must be complex enough to be engaging, but a model that is too complex or unpredictable will simply build tension to the point of frustration.

A good gameplay model requires balance and flow between these states.  This style of 3D momentum-based platforming is still in its infancy.  Once it has been perfected, there’s a whole new frontier of gameplay to be discovered.