Requirements and game rules in LLD - Deep Dive

Overview - Requirements and game rules

What is it?

Requirements and game rules define what a system or game must do and the boundaries within which it operates. Requirements describe the features, behaviors, and constraints needed for success. Game rules specify how players interact, what actions are allowed, and how outcomes are decided. Together, they guide design and ensure everyone understands the goals and limits.

Why it matters

Without clear requirements and rules, systems or games become confusing, unpredictable, and often fail to meet user needs. Imagine playing a game where no one agrees on how to win or what moves are allowed. Similarly, software without clear requirements often breaks or disappoints users. Clear rules and requirements create fairness, clarity, and a shared understanding that drives success.

Where it fits

Before learning about requirements and game rules, you should understand basic system components and user needs. After mastering this, you can explore detailed system design, architecture patterns, and implementation strategies. This topic is a foundation for planning any system or game effectively.

Mental Model

Core Idea

Requirements and game rules are the agreed instructions that define what a system or game must do and how it should behave.

Think of it like...

It's like a recipe and cooking instructions for a dish: the recipe lists ingredients (requirements), and the instructions tell you how to combine and cook them (rules) to get the final meal.

┌───────────────┐      ┌───────────────┐
│ Requirements  │─────▶│ Game Rules    │
│ (What to do)  │      │ (How to do it)│
└───────────────┘      └───────────────┘
          │                    │
          ▼                    ▼
      ┌─────────────────────────────┐
      │       System/Game Behavior   │
      └─────────────────────────────┘

Build-Up - 7 Steps

1

Foundation

Understanding Requirements Basics

Concept: Requirements specify what a system or game must achieve.

Requirements are statements that describe the desired features, functions, or constraints of a system or game. They answer questions like: What should the system do? What problems should it solve? For example, a game requirement might be 'Players can move in four directions.'

Result

You can clearly state what the system or game must do before building it.

Understanding requirements first prevents building something that doesn't meet user or player needs.

2

Foundation

Defining Game Rules Clearly

Concept: Game rules define how players interact and what is allowed.

Rules set the boundaries and procedures for gameplay. They explain what actions players can take, how turns work, and how to win or lose. For example, a rule might be 'Players cannot move through walls.'

Result

Players know how to play fairly and what to expect during the game.

Clear rules create fairness and prevent confusion or disputes during gameplay.

3

Intermediate

Distinguishing Functional and Non-Functional Requirements

🤔Before reading on: do you think all requirements describe what the system does, or do some describe how well it does it? Commit to your answer.

Concept: Requirements can be about what the system does (functional) or how well it does it (non-functional).

Functional requirements describe specific behaviors or functions, like 'The game must save progress.' Non-functional requirements describe qualities like performance, usability, or reliability, such as 'The game must load within 2 seconds.'

Result

You can categorize requirements to cover both behavior and quality aspects.

Knowing this distinction helps design systems that not only work but also perform well and satisfy users.

4

Intermediate

Capturing Requirements with User Stories

🤔Before reading on: do you think requirements are best written as technical specs or as simple stories from a user's view? Commit to your answer.

Concept: User stories describe requirements from the perspective of users or players.

A user story is a short, simple description of a feature told from the user's perspective, e.g., 'As a player, I want to save my game so I can continue later.' This helps keep requirements focused on real needs.

Result

Requirements become easier to understand and prioritize.

Using user stories connects technical work to real user goals, improving relevance and clarity.

5

Intermediate

Translating Rules into System Constraints

Concept: Game rules become constraints that the system enforces during operation.

Rules like 'Players cannot move through walls' translate into system checks that prevent illegal moves. The system must monitor actions and reject or handle those breaking rules.

Result

The system behaves predictably and enforces fairness automatically.

Understanding how rules become code constraints bridges design and implementation.

6

Advanced

Handling Conflicting or Changing Requirements

🤔Before reading on: do you think requirements always stay the same or can they change during development? Commit to your answer.

Concept: Requirements can conflict or evolve, requiring careful management.

Sometimes different stakeholders want opposing features, or new needs arise. Managing this involves prioritizing, negotiating, and updating requirements while keeping the system consistent.

Result

The system adapts to real-world changes without breaking.

Knowing how to handle changing requirements is key to building flexible, maintainable systems.

7

Expert

Formalizing Rules for Automated Verification

🤔Before reading on: do you think game rules are always informal, or can they be written so machines check them automatically? Commit to your answer.

Concept: Rules can be formalized into precise logic for automatic checking and testing.

By expressing rules in formal languages or logic, systems can verify compliance automatically, detect violations early, and ensure correctness. For example, using state machines or formal specifications.

Result

Higher confidence in system correctness and fewer bugs.

Formalizing rules enables automation that improves reliability and reduces human error.

Under the Hood

Requirements are gathered from stakeholders and documented clearly. Game rules are translated into system constraints and logic that control allowed actions and state changes. Internally, the system uses these rules to validate inputs, enforce limits, and determine outcomes. This often involves state machines, condition checks, and event handling to maintain consistent behavior.

Why designed this way?

This approach separates what the system must do (requirements) from how it enforces behavior (rules), making design clearer and modular. Historically, unclear requirements caused project failures, so formalizing them improved success rates. Rules as constraints ensure fairness and predictability, essential for games and reliable systems.

┌───────────────┐      ┌───────────────┐      ┌───────────────┐
│ Stakeholders  │─────▶│ Requirements  │─────▶│ System Design │
└───────────────┘      └───────────────┘      └───────────────┘
                                   │                      │
                                   ▼                      ▼
                           ┌───────────────┐      ┌───────────────┐
                           │ Game Rules    │─────▶│ Implementation│
                           └───────────────┘      └───────────────┘

Myth Busters - 4 Common Misconceptions

Quick: Do you think requirements are fixed and never change once written? Commit to yes or no.

Common Belief: Requirements are fixed and should never change after being written.

Reality: Requirements often evolve as understanding improves or conditions change.

Why it matters: Treating requirements as fixed can cause rigid systems that fail to meet real needs or adapt to new information.

Quick: Do you think game rules are just suggestions players can ignore? Commit to yes or no.

Common Belief: Game rules are just guidelines and can be bent or ignored without issue.

Reality: Rules are strict boundaries that must be enforced for fairness and correct gameplay.

Why it matters: Ignoring rules leads to unfair play, confusion, and broken systems.

Quick: Do you think all requirements must be functional, describing only what the system does? Commit to yes or no.

Common Belief: Requirements only describe system functions, not qualities like speed or reliability.

Reality: Non-functional requirements like performance and usability are equally important.

Why it matters: Ignoring non-functional requirements can result in systems that work but are slow, unreliable, or hard to use.

Quick: Do you think formalizing game rules is unnecessary overhead? Commit to yes or no.

Common Belief: Formalizing rules into logic or code is too complex and not worth the effort.

Reality: Formalization enables automatic verification, reducing bugs and increasing reliability.

Why it matters: Skipping formalization can cause subtle bugs and unpredictable behavior in complex systems.

Expert Zone

1

Requirements often contain hidden assumptions that must be uncovered through careful questioning.

2

Game rules can interact in complex ways, causing unexpected edge cases that require thorough testing.

3

Balancing strict enforcement of rules with flexibility for player creativity is a subtle design challenge.

When NOT to use

Rigid, formal requirements and rules may not suit highly exploratory or creative projects where flexibility is key. In such cases, lightweight or evolving guidelines and prototypes are better. Alternatives include agile user stories and iterative design.

Production Patterns

In production, requirements are managed with traceability tools linking them to code and tests. Game rules are implemented as modular components or rule engines to allow easy updates. Continuous validation ensures rules remain consistent as the system evolves.

Connections

Software Testing

Builds-on

Clear requirements and rules enable precise test cases that verify system correctness and prevent regressions.

Legal Contracts

Similar pattern

Both define agreed terms and conditions that govern behavior and resolve disputes, highlighting the importance of clarity and enforceability.

Traffic Laws

Analogous system

Traffic laws set rules for drivers to ensure safety and order, just as game rules maintain fairness and predictability.

Common Pitfalls

#1 Writing vague or incomplete requirements.

Wrong approach:

The system should be fast and user-friendly.

Correct approach:

The system must load the main screen within 2 seconds and allow users to complete tasks with no more than three clicks.

Root cause:

Assuming general statements are enough without measurable details leads to misunderstandings and poor design.

#2 Ignoring rule enforcement in implementation.

Wrong approach:

Allowing players to move anywhere without checks.

Correct approach:

Implementing checks that prevent players from moving through walls or outside boundaries.

Root cause:

Failing to translate rules into system constraints causes unpredictable and unfair behavior.

#3 Treating requirements as unchangeable.

Wrong approach:

Refusing to update requirements after stakeholder feedback.

Correct approach:

Incorporating feedback and revising requirements iteratively.

Root cause:

Misunderstanding that requirements evolve leads to rigid systems that don't meet real needs.

Key Takeaways

Requirements define what a system or game must do, while game rules define how it behaves and what is allowed.

Clear, measurable requirements and rules prevent confusion, ensure fairness, and guide successful design.

Requirements include both functional behaviors and non-functional qualities like performance and usability.

Rules must be translated into system constraints to enforce correct and predictable behavior automatically.

Managing changing requirements and formalizing rules improves system flexibility, reliability, and user satisfaction.