Game Loop

Written by: Akram Taghavi-Burris | © Copyright 2025

While the interaction loop covers a broader set of player-game system interactions, the game loop refers specifically to the core cycle that drives gameplay. This fundamental cycle that governs player interaction, decision-making, and feedback, is the continuous, repetitive sequence that keeps the gameplay experience alive, ensuring that actions and responses flow seamlessly from one to the next.

Core Game Loop

The core game loop is built around a cycle of key steps that keep gameplay moving forward. These steps involve the player's decisions, the game's reaction, and the feedback provided, all of which repeat continuously to create a dynamic and engaging experience. Let’s break down each element that makes up this fundamental cycle:

1. Decision – The player makes a choice based on the current context (e.g., explore the level or open the door).
2. Game Reaction – The game processes the decision (e.g., check if the player has the key).
3. Feedback – The game provides feedback to the player based on the result (e.g., the door stays locked or the player finds the key).
4. Repeat – The loop continues as the player progresses, making new decisions and receiving feedback until a new stage in the game is reached.

Example Game Loop

• Decision: The player decides whether to explore or go to the door.
  • If the player chooses to explore, the game checks if they find a key or an item.
  • If the player chooses to go to the door, the game checks if the player has the key.
• Game Reaction: The game reacts to this decision. If the player doesn’t have the key, the door remains locked. If the player goes exploring and finds the key, the key is added to their inventory.
• Feedback: The player is given feedback based on their decision. The door may stay locked with a sound indicating they need the key, or the key is collected, and they hear a sound of success.
• Repeat: This loop repeats until the player has the key and goes to the door, at which point the game progresses to the next level or ends.

This continuous cycle of decisions, reactions, and feedback is the engine that powers the gameplay experience. As players interact with the game world, the game loop ensures their actions are met with meaningful consequences, creating a dynamic and immersive experience that keeps the player engaged and progressing.

Object Interaction Loops

In addition to the main game loop, there are smaller loops that govern the behavior of specific objects or interactions within the game. These object-specific loops, though running in parallel to the core loop, manage the finer details of gameplay mechanics.

Example: Key Object Interaction

Consider the key from our example level:

1. Spawning – The key appears in the world, potentially respawning based on game conditions.
2. Collision – When the player comes into contact with the key, it is collected.
3. Destruction – If the key is not collected within a set time, it may disappear.

These object interaction loops help maintain the logic for each game element, ensuring that objects behave according to player actions and the rules of the game world. With a solid understanding of the main game loop and smaller object loops, we can start applying these concepts to game design. Mapping out these loops helps us break down complex systems into manageable components that can be iterated upon in a game engine like Unity.

Unity and Game Loops

In Unity, game loops governs how objects interact, how player input is processed, and how the game world responds over time. Unity’s script lifecycle is tightly integrated with this game loop, as it defines the sequence of events that occur when scripts are attached to game objects.

The script lifecycle refers to the automatic triggering of certain functions at specific points during the game’s runtime. These functions help manage how objects behave, respond to the player, and interact with the world around them. By understanding the order in which these events are called, you can better organize your gameplay logic and ensure your objects fit smoothly into the ongoing game loop.

Here’s a simple overview of when Unity’s lifecycle events occur within the context of the game loop:

1. Initialization Phase
   Early in the game, functions like Awake() and Start() are triggered. These are used to set up objects, initialize variables, and establish connections between different elements of the game world before gameplay begins.

2. Main Gameplay Loop
   Once gameplay starts, the core game loop is managed by functions like Update() and FixedUpdate(). These methods are called repeatedly during gameplay: Update()`` runs every frame, while FixedUpdate() is called at fixed time intervals, making it ideal for physics calculations and other real-time operations.

3. Final Adjustments
   After the main game loop processes the player’s actions and game objects, LateUpdate() is called. This event gives you the opportunity to adjust visual elements, like camera positioning or animations, after the rest of the game world has been updated.

4. Cleanup Phase
   When objects are no longer needed, Unity invokes the *OnDestroy()* function to clean up and release resources before removing them from the game world.

While Unity's script lifecycle is tied to the overall game loop, each game object with an attached script follows its own sequence of events, essentially creating a smaller, object-specific interaction loop. This means every object in the game (e.g., characters, items, or environmental elements) has a unique set of lifecycle events that manage its behavior and interaction with other objects.

For example, a character object may have its Awake(), Start(), and Update() functions to control its movement, detect collisions, and update animations. These lifecycle events work in parallel to the core game loop, which governs player decisions, game reactions, and feedback. In this sense, the object’s lifecycle is like a micro-loop within the broader gameplay loop, focusing on how the object reacts to inputs, interacts with the world, and updates its state.

Here’s how the object-specific interaction loop might play out in this context:

1. Spawning: An object appears in the game world, triggering its initialization phase (e.g., Awake() and Start()).
2. Interaction:
   • Every frame of the game an object reacts to player input or other game events during the Update() (e.g., moving when the player presses a button).
   • If the object collides with another object (e.g., the player touches a wall or picks up an item), the OnCollision or OnTrigger methods (e.g., OnCollisonEnter() , OnTriggerEnter) are triggered. These methods allow the object to respond to physical interactions, such as taking damage, bouncing off surfaces, or collecting items.

Collision vs Trigger

In Unity, collisions occur when objects physically interact, triggering a physcs reactions like bouncing or stopping. Triggers, on the other hand, detect when objects enter or exit an area without any physical response and are used when for non-physical events like pickups or area detection.

3. Reaction: The object’s state changes based on interactions and feedback is generated. For example, if the player character touches an item (and it triggers a collision), the item might be collected, and the character’s inventory updates. Visual feedback, such as animations or sound effects, might also play.
4. Destruction/Removal: When the object is no longer needed (e.g., it’s destroyed or deactivated), Unity calls the OnDestroy() function to clean up the object and release resources.

While each object has its own lifecycle of events, these are tightly integrated into the broader game loop, where the game's continuous cycle of decisions, reactions, and feedback also drives how individual objects behave, react, and interact with other elements in the game.

By understanding this connection between the object-specific script lifecycle and object interaction loops, you gain a deeper insight into how the game world operates on a granular level. This parallel structure ensures that both the game as a whole and the individual objects behave predictably, interacting seamlessly within the larger system.