Sculpt: A Game Development Journal

Welcome to Project Sculpt: A Tabletop Roleplaying Game Development Journal

Here, I discuss all aspects of the tabletop roleplaying game Sculpt.

New to Project Sculpt? See the Overview here.

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The Dice Roll: Opposed Step-Die

Criteria I used when deciding on the dice system for Sculpt.

Choosing the Right System

One key aspect of Sculpt as a system are the die rolls used to determine success and failure. I wanted to use a system that had variable success rates and magnitudes of success and failure. I decided to use an opposed step-die system; one variable die, a d2 through a d12, is rolled against another, and the higher of the two die rolls determines the final outcome. Each roll has an instigator and a target, and if the instigator rolls the higher value, they are successful at performing the action being attempted; if the target’s roll is higher, the target is successful in resisting the action being attempted. I settled on this system by taking into account desirable percent chances of success and failure as well as the feel making a roll has within the game.

Percent Chances of Success

One of the first aspects I had to concretely define were the desired percent chances of success. If I made success too likely, players felt like rolling was trivial and failure was a fluke; if I made success too rare, players felt like rolling was pointless and failure was inevitable. There was a hard balance to strike, but over testing multiple systems, I was able to hone on the thresholds that felt right for Sculpt. Throughout this process, I found that:

40-45 percent chance rolls fit well with player expectations of success for a difficult roll.
Frequent 50 percent chance rolls felt like a character’s abilities were not being taken into account, that only chance is at play.
60-70 percent chance rolls fit well with player expectations of success for a fair, or average, roll.
70-85 percent chance rolls fit will with player expectations of success for a skilled roll.
85 percent chance rolls and higher started to diminish the feeling of rolling for success and instead put the emphasis on “roll to not fail".

Using these thresholds as a guide, I was able to more easily tailor Sculpt’s die system to meet the desired expectations of players. I knew I wanted a more challenging feeling for the game, so I used a system where the percent chance of success is at the lower end each range.

Feel of Gameplay

Another key aspect I wanted to define was the in-game feel of making a roll. Single die rolls, additive rolls, comparative rolls, they all have a unique feel to the player, and based on player feedback, I found that:

Rolling a single die trying to overcome a success threshold felt like chance was the main opposition to the roll.
Adding multiple, similar die felt like trying to beat an average or threshold semi-arbitrarily.
Adding multiple, variable die felt like contributing factors scaled too quickly or not enough.
Comparing multiple, similar die felt like character traits were either too heavily favored or completely ignored.
Comparing multiple, variable die felt like character traits were tempered in their range and scope.

Using these player feelings, I was able to narrow in on my desired feel for die rolls that fit with player expectations of a more challenging system. I knew that I wanted a system where a character’s traits directly opposed a target’s, and players should be able to quickly gauge how their character’s traits impact the roll.

These two system aspects, percent chance of success and the feel of gameplay, ultimately led me to the opposed step-die system that Sculpt utilizes. It quite neatly fit within the player’s expected percent chance of success while allowing for growth, and it fit with the feel of gameplay where actions are opposed or resisted, and power is easily gauged by the size of the die being rolled.

Comparing Considered Systems

1d20

The first system I tested was 1d20 + modifier vs challenge rating. This system was both the easiest to manipulate and also gave the largest range in rolls. The flat distribution of roll outcomes that came from rolling a single die provided a strong framework to build on, but I ultimately saw the system as unreliable. Suffering from a known issue with single die systems, there were large swings in outcomes, and the predictability of whether an individual roll would likely result in success or failure was hard to accurately gauge. While the percent chance of success for each roll was easy to determine, each change in modifier or roll represents +/-5%, the feel of the roll didn’t quite fit with the expectations that players had in terms of actions being resisted by similar factors.

2dX

One of the last systems I tested, 2dX vs thresholds of success gave a much more predictable and intuitive roll, but ultimately, the system didn’t provide the right framework for variable success. Rolling 2d4 vs rolling 2d8 have drastically different sums, and this pushed the expected percent chance of success too low for lesser die being rolled in challenging circumstances. While the feel of the roll was within player’s expectations for actions being opposed, the system was brutally unfair to weaker rolls and overemphasized conditional modifiers.

Opposed Step-Die

The system I ended up adapting for Sculpt, opposed step-die hit a sweet-spot in terms of both providing a spread of percent chance of success and the player described feel of making the rolls fit with the opposed nature of the game I was searching for. It combines the probabilities of rolling larger die being more likely to beat a smaller die, and the comparative, rather than additive, function of the roll creates the right feeling of opposition.

Opposed Step-Die Breakdown

Sculpt’s opposed step-die system gives a distinct curve in success rates; rolling a d2 or a d4, regardless of the die you are rolling against, alters the likelihood of success in meaningful ways. Additionally, the comparative nature of each roll means that rolling against varying die alters the average difference of each roll. These two factors combine into a system where the higher the die your roll makes it more likely that you succeed, and more likely that you succeed by a wider margin. Lastly, the opposed nature of the roll creates a mechanical feel of opposition and challenge. Together these traits make the opposed step-die system perfect for what I was trying to accomplish.