Unity Level Design

Level Design -- Design Translation Patterns

Prerequisite skills: unity-scene-assets (additive scenes, Addressables), unity-async-patterns (async loading, cancellation), unity-game-architecture (SO events, bootstrap)

Claude treats levels as static scene files with no contract layer between level designers and gameplay programmers. Triggers are one-off scripts with game logic jammed into OnTriggerEnter, encounters are hardcoded spawn sequences, and checkpoints break on scene reload because nobody thought about what state needs to survive. These patterns establish the translation layer: designers author intent through data assets and Inspector configuration, programmers provide the systems that honor that intent.

PATTERN 1: Trigger & Event Architecture

DESIGN INTENT: Level designers place trigger volumes in the editor that fire game events -- spawn enemies, play dialogue, open a door. The trigger is a generic, reusable component; the response is wired in the Inspector via ScriptableObject event channels.

WRONG:

// Each trigger is a bespoke script -- 47 of these in the project
public class Door3Trigger : MonoBehaviour
{
    public GameObject door;
    void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Player"))
            door.GetComponent<Animator>().SetTrigger("Open");
    }
}

Every trigger is a unique MonoBehaviour. No reuse, no designer control, no way to disable or reconfigure without code changes.

RIGHT: Generic TriggerZone component with configurable activation rules and SO event channel output. Designer wires event in Inspector -- zero per-trigger code.

using UnityEngine;

/// <summary>
/// Generic trigger volume that raises a GameEvent SO channel on activation.
/// Configurable activation count, tag filter, cooldown, and delay.
/// </summary>
[RequireComponent(typeof(Collider), typeof(Rigidbody))]
public class TriggerZone : MonoBehaviour
{
    public enum ActivationMode { Once, Repeating, NTimes }

    [Header("Activation Rules")]
    [SerializeField] ActivationMode _mode = ActivationMode.Once;
    [SerializeField] int _maxActivations = 1;
    [SerializeField] float _cooldownSeconds;
    [SerializeField] float _activationDelay;
    [SerializeField] string _requiredTag = "Player";
    [SerializeField] LayerMask _requiredLayer = ~0;

    [Header("Event Output")]
    [SerializeField] GameEvent _onActivated;

    int _activationCount;
    float _lastActivationTime = float.NegativeInfinity;

    // See unity-game-architecture for GameEvent SO channel pattern

    void Reset()
    {
        // Guarantee Rigidbody is kinematic and collider is trigger
        var rb = GetComponent<Rigidbody>();
        rb.isKinematic = true;
        GetComponent<Collider>().isTrigger = true;
    }

    void OnTriggerEnter(Collider other)
    {
        if (!PassesFilter(other)) return;
        if (!CanActivate()) return;
        _ = ActivateAsync();
    }

    bool PassesFilter(Collider other)
    {
        if (!string.IsNullOrEmpty(_requiredTag) && !other.CompareTag(_requiredTag))
            return false;
        if ((_requiredLayer & (1 << other.gameObject.layer)) == 0)
            return false;
        return true;
    }

    bool CanActivate()
    {
        if (_mode == ActivationMode.Once && _activationCount >= 1) return false;
        if (_mode == ActivationMode.NTimes && _activationCount >= _maxActivations) return false;
        if (Time.time - _lastActivationTime < _cooldownSeconds) return false;
        return true;
    }

    async Awaitable ActivateAsync()
    {
        if (_activationDelay > 0f)
            await Awaitable.WaitForSecondsAsync(_activationDelay, destroyCancellationToken);

        _activationCount++;
        _lastActivationTime = Time.time;
        _onActivated?.Raise();
    }
}

SCAFFOLD:

• TriggerZone MonoBehaviour (above) -- the generic trigger component
• GameEvent ScriptableObject channel -- cross-ref unity-game-architecture
• TriggerConfig fields -- activation mode, count, cooldown, delay, tag/layer filter

DESIGN HOOK: Designers place trigger volumes in the scene, assign a GameEvent SO in the Inspector, and configure activation rules. Zero per-trigger code. New trigger behaviors = new GameEvent listeners, not new trigger scripts.

GOTCHA: OnTriggerEnter requires one collider to have isTrigger = true and at least one Rigidbody in the pair. The TriggerZone adds its own kinematic Rigidbody via [RequireComponent] and sets it up in Reset() to guarantee this works regardless of what enters. Without this, triggers silently fail when the entering object has no Rigidbody.

PATTERN 2: Encounter Design Contracts

DESIGN INTENT: Designers define encounters (enemy waves, arena lockdowns, puzzles) as data assets and place them in levels via prefabs. The encounter definition is separate from the encounter instance.

WRONG:

// Hardcoded encounter -- can't reuse, can't tune without code changes
public class ArenaEncounter : MonoBehaviour
{
    public GameObject zombiePrefab;
    public GameObject skeletonPrefab;

    async Awaitable Start()
    {
        // Wave 1
        Instantiate(zombiePrefab, transform.position, Quaternion.identity);
        Instantiate(zombiePrefab, transform.position + Vector3.right * 3, Quaternion.identity);
        await Awaitable.WaitForSecondsAsync(10f);
        // Wave 2
        Instantiate(skeletonPrefab, transform.position, Quaternion.identity);
    }
}

Every encounter is a unique script. Wave timing, enemy types, and spawn positions are all hardcoded.

RIGHT: EncounterConfig SO defines waves as data. EncounterController prefab reads the config and manages spawning.

using System;
using UnityEngine;

/// <summary>
/// Defines a single wave within an encounter: enemy types, counts, and timing.
/// </summary>
[Serializable]
public struct WaveDefinition
{
    /// <summary>Enemy prefab to spawn in this wave.</summary>
    public GameObject EnemyPrefab;
    /// <summary>Number of enemies to spawn.</summary>
    public int Count;
    /// <summary>Seconds to wait before starting this wave (after previous completes).</summary>
    public float DelayBeforeWave;
    /// <summary>If true, all enemies must be defeated before next wave starts.</summary>
    public bool WaitForClear;
}

/// <summary>
/// Data asset defining an entire encounter: sequence of waves and completion rules.
/// </summary>
[CreateAssetMenu(menuName = "Level Design/Encounter Config")]
public class EncounterConfig : ScriptableObject
{
    /// <summary>Ordered list of waves in this encounter.</summary>
    public WaveDefinition[] Waves;
    /// <summary>Event raised when the encounter begins.</summary>
    public GameEvent OnEncounterStart;
    /// <summary>Event raised when all waves are cleared.</summary>
    public GameEvent OnEncounterComplete;
}

using System.Collections.Generic;
using System.Threading;
using UnityEngine;

/// <summary>
/// Runs an encounter defined by an EncounterConfig SO.
/// Place in scene with spawn point transforms as children.
/// </summary>
public class EncounterController : MonoBehaviour
{
    [SerializeField] EncounterConfig _config;
    [SerializeField] Transform[] _spawnPoints;
    [SerializeField] GameEvent _triggerEvent; // Listens for this to start

    readonly List<GameObject> _activeEnemies = new();

    // Full implementation in references/level-system-scaffolds.md
}

SCAFFOLD:

• EncounterConfig SO -- wave definitions, completion events
• WaveDefinition serializable struct -- enemy prefab, count, timing, clear condition
• EncounterController MonoBehaviour -- async wave progression, spawn management

DESIGN HOOK: Designers create EncounterConfig SOs per encounter and place EncounterController prefabs at encounter locations. Spawn points are child Transforms on the controller. Tuning wave counts, timing, and enemy types requires zero code changes.

GOTCHA: Spawn points must be defined per-encounter in the scene (Transform array on the controller), not in the SO. ScriptableObjects cannot reference scene objects -- they are project-level assets. If you put Transform references in the SO, they will be null at runtime.

PATTERN 3: Checkpoint & Respawn

DESIGN INTENT: Players die and respawn at the last activated checkpoint. Checkpoint state survives across attempts -- doors stay opened, keys stay collected, enemies stay dead.

WRONG:

// Full scene reload on death -- all progress lost
public class DeathHandler : MonoBehaviour
{
    public void OnPlayerDied()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().name);
    }
}

Reloading the scene resets everything. Doors re-lock, enemies respawn, puzzles reset. The player must redo the entire level.

RIGHT: CheckpointSystem captures a CheckpointSnapshot on activation. On death, the snapshot is restored without a scene reload. Objects that need save/restore implement ICheckpointable.

using UnityEngine;

/// <summary>
/// Implement on any object that needs to save/restore state at checkpoints.
/// </summary>
public interface ICheckpointable
{
    /// <summary>Unique ID for this object (use a serialized GUID).</summary>
    string CheckpointId { get; }
    /// <summary>Capture current state as serializable data.</summary>
    object CaptureState();
    /// <summary>Restore state from previously captured data.</summary>
    void RestoreState(object state);
}

using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// Snapshot of all checkpointable state at a specific checkpoint.
/// </summary>
public class CheckpointSnapshot
{
    /// <summary>Player position at checkpoint activation.</summary>
    public Vector3 PlayerPosition;
    /// <summary>Player rotation at checkpoint activation.</summary>
    public Quaternion PlayerRotation;
    /// <summary>Saved state per checkpointable object, keyed by CheckpointId.</summary>
    public Dictionary<string, object> ObjectStates = new();
}

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

/// <summary>
/// Manages checkpoint save/restore. Singleton, lives in persistent scene.
/// </summary>
public class CheckpointSystem : MonoBehaviour
{
    public static CheckpointSystem Instance { get; private set; }

    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
    static void ResetStatics() => Instance = null;

    CheckpointSnapshot _currentSnapshot;

    void Awake()
    {
        if (Instance != null && Instance != this) { Destroy(gameObject); return; }
        Instance = this;
    }

    /// <summary>
    /// Captures a checkpoint snapshot from the player and all ICheckpointable objects.
    /// </summary>
    public void SaveCheckpoint(Transform player)
    {
        _currentSnapshot = new CheckpointSnapshot
        {
            PlayerPosition = player.position,
            PlayerRotation = player.rotation
        };

        foreach (var obj in FindCheckpointables())
            _currentSnapshot.ObjectStates[obj.CheckpointId] = obj.CaptureState();
    }

    /// <summary>
    /// Restores the last checkpoint snapshot. Returns false if no checkpoint exists.
    /// </summary>
    public bool RestoreCheckpoint(Transform player)
    {
        if (_currentSnapshot == null) return false;

        player.position = _currentSnapshot.PlayerPosition;
        player.rotation = _currentSnapshot.PlayerRotation;

        foreach (var obj in FindCheckpointables())
        {
            if (_currentSnapshot.ObjectStates.TryGetValue(obj.CheckpointId, out var state))
                obj.RestoreState(state);
        }
        return true;
    }

    IEnumerable<ICheckpointable> FindCheckpointables() =>
        FindObjectsByType<MonoBehaviour>(FindObjectsSortMode.None).OfType<ICheckpointable>();
}

SCAFFOLD:

• CheckpointSystem manager (singleton, persistent scene) -- save/restore orchestration
• CheckpointSnapshot -- player transform + dictionary of object states
• ICheckpointable interface -- CaptureState() / RestoreState(object)
• CheckpointTrigger -- extends TriggerZone pattern (Pattern 1) to call CheckpointSystem.SaveCheckpoint

DESIGN HOOK: Objects implement ICheckpointable to participate in checkpoint save/restore (doors, switches, destructibles). Designers place checkpoint trigger volumes in the scene. The system handles the rest.

GOTCHA: The checkpoint must save ALL mutable state. If a door was opened between checkpoints, the opened state must be in the snapshot. Audit every gameplay object for ICheckpointable -- a single missing implementation means that object resets on death while everything else restores, creating impossible states. Also: FindObjectsByType is expensive -- cache the results if checkpoints are frequent.

PATTERN 4: Cinematic & Scripted Sequences

DESIGN INTENT: In-game cutscenes, camera moves, NPC dialogue, and timed events as authored sequences that designers compose in the Inspector without writing code.

WRONG:

// Coroutine chain -- fragile, not reusable, not skippable
IEnumerator PlayCutscene()
{
    camera.transform.position = new Vector3(10, 5, 0);
    yield return new WaitForSeconds(2f);
    npc.GetComponent<Animator>().SetTrigger("Talk");
    dialogueUI.Show("Welcome, hero!");
    yield return new WaitForSeconds(3f);
    door.SetActive(false);
}

Hardcoded positions, no cancellation, not skippable, uses deprecated coroutine pattern.

RIGHT: ISequenceStep interface with async ExecuteAsync(CancellationToken). SequencePlayer runs steps in order. Steps are composed in the Inspector via [SerializeReference].

using System.Threading;

/// <summary>
/// A single step in a scripted sequence. Implement for each step type.
/// </summary>
public interface ISequenceStep
{
    /// <summary>
    /// Execute this step. Must respect cancellation for skip support.
    /// When cancelled, the step should immediately apply its end state.
    /// </summary>
    Awaitable ExecuteAsync(CancellationToken ct);
}

using System;
using System.Collections.Generic;
using System.Threading;
using UnityEngine;

/// <summary>
/// Plays a sequence of ISequenceStep instances in order.
/// Steps are composed via [SerializeReference] in the Inspector.
/// </summary>
public class SequencePlayer : MonoBehaviour
{
    [SerializeReference] List<ISequenceStep> _steps = new();
    [SerializeField] bool _playOnStart;
    [SerializeField] GameEvent _onSequenceComplete;

    bool _isPlaying;

    /// <summary>Play the full sequence. Cancellation skips remaining steps.</summary>
    public async Awaitable PlayAsync(CancellationToken ct = default)
    {
        if (_isPlaying) return;
        _isPlaying = true;

        using var linked = CancellationTokenSource.CreateLinkedTokenSource(
            ct, destroyCancellationToken);

        foreach (var step in _steps)
        {
            if (linked.Token.IsCancellationRequested) break;

            try
            {
                await step.ExecuteAsync(linked.Token);
            }
            catch (OperationCanceledException)
            {
                break;
            }
        }

        _isPlaying = false;
        _onSequenceComplete?.Raise();
    }

    async void Start()
    {
        if (_playOnStart)
            await PlayAsync(destroyCancellationToken);
    }
}

Example step implementations:

using System;
using System.Threading;
using UnityEngine;

/// <summary>Wait for a specified duration. Skippable via cancellation.</summary>
[Serializable]
public class WaitStep : ISequenceStep
{
    [SerializeField] float _duration = 1f;

    public async Awaitable ExecuteAsync(CancellationToken ct)
    {
        await Awaitable.WaitForSecondsAsync(_duration, ct);
    }
}

/// <summary>Enable or disable a GameObject.</summary>
[Serializable]
public class SetActiveStep : ISequenceStep
{
    [SerializeField] GameObject _target;
    [SerializeField] bool _active = true;

    public Awaitable ExecuteAsync(CancellationToken ct)
    {
        if (_target != null) _target.SetActive(_active);
        return Awaitable.NextFrameAsync(ct);
    }
}

SCAFFOLD:

• ISequenceStep interface -- ExecuteAsync(CancellationToken)
• SequencePlayer MonoBehaviour -- runs [SerializeReference] step list in order
• Step types: CameraMoveStep, DialogueStep, WaitStep, SetActiveStep

DESIGN HOOK: New sequence step = implement ISequenceStep. Designers compose sequences in the Inspector by adding/removing/reordering steps in the [SerializeReference] list. No code changes to create new cutscenes.

GOTCHA: [SerializeReference] requires concrete types in the same assembly or an assembly that references the interface assembly. Unity's default Inspector does not provide a nice UI for [SerializeReference] -- you need a custom PropertyDrawer or use a package like Odin Inspector / SerializeReferenceDropdown. Steps must handle cancellation gracefully: when cancelled (skip), apply the end state immediately (e.g., snap camera to final position) rather than leaving the step half-complete.

PATTERN 5: Environmental Storytelling Hooks

DESIGN INTENT: Objects react to player proximity or interaction -- notes to read, audio logs to play, environmental animations to trigger. All interactive objects share a consistent UX pattern.

WRONG:

// Each interactive object is a unique script with bespoke logic
public class Note47 : MonoBehaviour
{
    void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Player") && Input.GetKeyDown(KeyCode.E))
            UIManager.Instance.ShowNote("Note 47 text...");
    }
}

No shared interaction UX. Each object checks input differently. Prompt display is inconsistent. New interaction types require new scripts from scratch.

RIGHT: Interactable component with IInteraction interface. Shared InteractionDetector on the player handles proximity detection and input prompting.

using UnityEngine;

/// <summary>
/// Interface for interaction behaviors. Implement per interaction type.
/// </summary>
public interface IInteraction
{
    /// <summary>Text shown on the interaction prompt (e.g., "Read Note").</summary>
    string PromptText { get; }
    /// <summary>Execute the interaction.</summary>
    void Execute(GameObject interactor);
}

using UnityEngine;

/// <summary>
/// Marks a GameObject as interactable. Holds an IInteraction and detection range.
/// </summary>
public class Interactable : MonoBehaviour
{
    [SerializeField] float _interactionRange = 2f;
    [SerializeReference] IInteraction _interaction;

    /// <summary>Maximum distance for interaction.</summary>
    public float InteractionRange => _interactionRange;
    /// <summary>The interaction behavior attached to this object.</summary>
    public IInteraction Interaction => _interaction;
}

using System.Collections.Generic;
using System.Linq;
using UnityEngine;

/// <summary>
/// Player-side component. Detects nearby Interactables and handles input prompting.
/// Cross-ref unity-input-correctness for input handling.
/// </summary>
public class InteractionDetector : MonoBehaviour
{
    [SerializeField] float _detectionRadius = 5f;
    [SerializeField] LayerMask _interactableLayer;

    Interactable _currentTarget;
    readonly Collider[] _overlapBuffer = new Collider[16];

    void Update()
    {
        _currentTarget = FindClosestInteractable();

        if (_currentTarget != null)
        {
            ShowPrompt(_currentTarget.Interaction.PromptText);
            // Input check -- see unity-input-correctness for Input System usage
        }
        else
        {
            HidePrompt();
        }
    }

    Interactable FindClosestInteractable()
    {
        int count = Physics.OverlapSphereNonAlloc(
            transform.position, _detectionRadius, _overlapBuffer, _interactableLayer);

        Interactable closest = null;
        float closestDist = float.MaxValue;

        for (int i = 0; i < count; i++)
        {
            if (!_overlapBuffer[i].TryGetComponent<Interactable>(out var interactable))
                continue;

            float dist = Vector3.Distance(transform.position, interactable.transform.position);
            if (dist > interactable.InteractionRange) continue;
            if (dist < closestDist)
            {
                closest = interactable;
                closestDist = dist;
            }
        }
        return closest;
    }

    void ShowPrompt(string text) { /* UI Toolkit prompt -- see implementation in scaffolds */ }
    void HidePrompt() { /* Hide prompt UI */ }
}

SCAFFOLD:

• Interactable MonoBehaviour -- holds IInteraction via [SerializeReference], detection range
• IInteraction interface -- PromptText, Execute(GameObject interactor)
• InteractionDetector on player -- proximity detection, prompt display, input handling
• Example: ReadNoteInteraction implements IInteraction

DESIGN HOOK: New interaction type = implement IInteraction. Designers configure prompt text, range, and interaction type on the prefab. Consistent UX across all interactive objects.

GOTCHA: Interaction prompt must use world-to-screen positioning (Camera.main.WorldToScreenPoint) and handle off-screen clamping. Use Physics.OverlapSphereNonAlloc with a pre-allocated buffer -- do not allocate every frame. Camera.main is a FindObjectWithTag call under the hood; cache the camera reference.

PATTERN 6: Level Streaming & Loading Seams

DESIGN INTENT: Large levels load/unload sections as the player moves -- open world, long corridors, hub with connected areas. The player never sees a loading screen during gameplay.

WRONG:

// Entire world in one scene
// 500 MB memory usage, 45-second load time, untestable

Everything in one scene. Artists can't work in parallel (merge conflicts). Memory usage is unbounded. Initial load time grows forever.

RIGHT: StreamingVolume trigger zones that additively load/unload scene chunks via Addressables (cross-ref unity-scene-assets). Preloading based on player proximity. Hysteresis to prevent thrashing.

using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.ResourceManagement.ResourceProviders;

/// <summary>
/// Configuration for a streamable level chunk.
/// </summary>
[CreateAssetMenu(menuName = "Level Design/Level Chunk Config")]
public class LevelChunkConfig : ScriptableObject
{
    /// <summary>Addressable scene asset reference for this chunk.</summary>
    public AssetReference SceneReference;
    /// <summary>Distance at which to begin preloading this chunk.</summary>
    public float PreloadDistance = 50f;
    /// <summary>Distance at which to unload this chunk (must be > PreloadDistance).</summary>
    public float UnloadDistance = 80f;
}

using System.Threading;
using UnityEngine;
using UnityEngine.AddressableAssets;
using UnityEngine.ResourceManagement.AsyncOperations;
using UnityEngine.ResourceManagement.ResourceProviders;
using UnityEngine.SceneManagement;

/// <summary>
/// Manages loading/unloading a level chunk based on player proximity.
/// Place at the seam between level sections.
/// Cross-ref unity-scene-assets for Addressable scene loading patterns.
/// </summary>
public class StreamingVolume : MonoBehaviour
{
    [SerializeField] LevelChunkConfig _chunkConfig;
    [SerializeField] Transform _playerTransform;

    AsyncOperationHandle<SceneInstance> _loadHandle;
    bool _isLoaded;
    bool _isLoading;

    void Update()
    {
        if (_playerTransform == null) return;
        float distance = Vector3.Distance(transform.position, _playerTransform.position);

        if (!_isLoaded && !_isLoading && distance < _chunkConfig.PreloadDistance)
            _ = LoadChunkAsync(destroyCancellationToken);
        else if (_isLoaded && distance > _chunkConfig.UnloadDistance)
            _ = UnloadChunkAsync();
    }

    async Awaitable LoadChunkAsync(CancellationToken ct)
    {
        _isLoading = true;
        _loadHandle = Addressables.LoadSceneAsync(
            _chunkConfig.SceneReference, LoadSceneMode.Additive);

        while (!_loadHandle.IsDone)
        {
            ct.ThrowIfCancellationRequested();
            await Awaitable.NextFrameAsync(ct);
        }

        _isLoaded = true;
        _isLoading = false;
    }

    async Awaitable UnloadChunkAsync()
    {
        if (!_loadHandle.IsValid()) return;
        var unload = Addressables.UnloadSceneAsync(_loadHandle);

        while (!unload.IsDone)
            await Awaitable.NextFrameAsync(destroyCancellationToken);

        _isLoaded = false;
    }

    void OnDestroy()
    {
        if (_isLoaded && _loadHandle.IsValid())
            Addressables.UnloadSceneAsync(_loadHandle);
    }
}

SCAFFOLD:

• StreamingVolume MonoBehaviour -- proximity-based load/unload with hysteresis
• LevelChunkConfig SO -- scene reference, preload distance, unload distance
• Async Addressable scene loading/unloading (cross-ref unity-scene-assets)

DESIGN HOOK: Designers place streaming volumes at level seams and assign chunk configs. Chunk configs define which Addressable scene to load and at what distances. Preload distance < unload distance provides hysteresis.

GOTCHA: Adjacent chunks must share a small overlap zone. Objects at the seam (e.g., a bridge between two areas) must exist in both chunks or in a persistent scene that is never unloaded. The unload distance must be strictly greater than the preload distance (hysteresis buffer) -- otherwise the system will thrash between loading and unloading every frame. Test with Profiler.GetTotalAllocatedMemoryLong() to verify chunks are actually freeing memory on unload.

Anti-Patterns Summary

Related Skills

• unity-game-architecture -- GameEvent SO channel pattern, bootstrap scene, SO-based config
• unity-scene-assets -- Addressable asset loading, additive scene management
• unity-async-patterns -- Awaitable usage, cancellation tokens, async lifecycle
• unity-input-correctness -- Input System integration for interaction prompts
• unity-save-system -- Persistent save data (checkpoint snapshots are transient; save system is permanent)
• unity-physics -- Trigger collider setup, layer-based filtering, Rigidbody requirements

Additional Resources

• Unity Manual: Scene Loading
• Unity Manual: Addressables
• Unity Manual: SerializeReference
• Unity Manual: ScriptableObject