## Instructions - Use URP 2D Renderer + 2D packages (Tilemap, Sprite Atlas, Cinemachine, Input System); target Unity 2022 LTS+. - Paint levels with Tilemaps + RuleTiles: one Tilemap per layer (Ground, Decor, Collision), TilemapCollider2D + Composite for perf. - Pack sprites with Sprite Atlas (tight packing, 2048 max, Crunch for mobile); set PPU 16/32 consistently, filter Point for pixel-art. - Drive physics with Rigidbody2D (Dynamic for player, Kinematic for movers): interpolate, Continuous collision for fast bodies. - Frame camera with Cinemachine 2D: Framing Transposer + Confiner (Tilemap bounds), Pixel Perfect Camera for retro looks. - Manage depth with Sorting Layers (Background/World/Foreground) + Order in Layer; use Y-sort for top-down via SortingGroup. - Animate with Animator + 2D Animation (bones) or simple sprite-swap; use Animation Events for footstep/hit triggers. - Handle input via Input System actions (Move/Jump/Dash) with keyboard+gamepad+touch bindings; add on-screen sticks for mobile. - Optimize mobile 2D: sprite atlas reuse, disable shadows, cap particles, pool projectiles, Application.targetFrameRate 60. - Persist with JSON in Application.persistentDataPath; version saves, backup slot, test cold start + upgrade path. - Profile with Profiler 2D Physics + Frame Debugger; keep draw calls <80 mobile, overdraw low, GC alloc zero in Update. - Ship with Addressables for levels/skins; build profiles for Android (ETC2) + iOS (ASTC), test on low-end device. ## Examples - Example 1 — Platformer Tilemap: RuleTile ground + CompositeCollider, player Rigidbody2D Dynamic, coyote 0.1s, jump buffer wired via Input. - Example 2 — Top-down Y-sort: SortingGroup on props, Transparency Sort Axis Y=1, Cinemachine confiner locked to level bounds. - Example 3 — Mobile runner: Sprite Atlas packed env, pooled coins (50), Pixel Perfect on, 60fps locked on Pixel 4a test. ## Workflows 1. Setup: URP 2D template, PPU 32, Input Actions asset, Sorting Layers, Atlas v1, Cinemachine confiner from Tilemap. 2. Level: paint RuleTile ground, add hazards/pickups prefabs, Camera follow + parallax 0.5 layers, playtest jump feel. 3. Systems: health/inventory singletons, save/load JSON, HUD (TMP) + pause, audio mixer groups, pool manager. 4. Mobile pass: atlas crunch, touch controls, targetFrameRate, profiler on device, reduce overdraw + colliders. 5. Ship: Addressables build, Android App Bundle + TestFlight, store icons/screenshots, staged rollout with crash reporting. ## Templates ### Unity C# 2D Controller (Rigidbody2D) ```csharp using UnityEngine; using UnityEngine.InputSystem; [RequireComponent(typeof(Rigidbody2D))] public class Player2D : MonoBehaviour { public float speed = 7f, jumpForce = 13f; Rigidbody2D rb; Vector2 move; float coyote, buffer; void Awake(){ rb = GetComponent(); rb.interpolation = RigidbodyInterpolation2D.Interpolate; } public void OnMove(InputValue v){ move = v.Get(); } public void OnJump(InputValue v){ if(v.isPressed) buffer = 0.12f; } void Update(){ coyote -= Time.deltaTime; buffer -= Time.deltaTime; float tx = move.x * speed; rb.linearVelocity = new Vector2(tx, rb.linearVelocity.y); if(buffer>0 && coyote>0){ rb.linearVelocity = new Vector2(rb.linearVelocity.x, jumpForce); buffer=0; coyote=0; } } void OnCollisionEnter2D(Collision2D c){ if(c.contacts[0].normal.y > 0.7f) coyote = 0.1f; } } ``` ### RuleTile + Sorting Setup ``` Tilemaps: Ground(RuleTile, Collider+Composite) / Decor(NoCollider) / Hazards(IsTrigger) Sorting Layers: BG(0) < Ground(5) < Entities(10) < FX(20) < UI(100) Sprite Atlas: 2048, padding 4, Crunch 75 mobile / Truecolor PC Cinemachine: vcam Follow=Player, DeadZone 0.3, Confiner=LevelBounds Collider ``` ### Pool Manager snippet ```csharp public class Pool : MonoBehaviour { public GameObject prefab; public int size=40; Queue q=new(); void Start(){ for(int i=0;i0?q.Dequeue():Instantiate(prefab,transform);o.transform.position=p;o.SetActive(true);return o;} public void Release(GameObject o){o.SetActive(false);q.Enqueue(o);} } ``` ## Tools - Unity 2022 LTS, URP 2D, Tilemap Extras (RuleTile), Sprite Atlas, Cinemachine, Input System, TextMeshPro. - Profiler + Frame Debugger, Addressables, Cloud Diagnostics/Crashlytics, git + LFS for art. - Aseprite, Tiled importer, Kenney 2D packs, PrimeTween/DOTween for juice. ## Advanced - Use 2D lights (Freeform/Point) sparingly on mobile; bake glow into sprites, use normal maps only on hero assets. - Implement predictive touch: fixed timestep 60Hz, max 3 substeps, deterministic pickups via seed; test airplane-mode saves. - Automate builds with Build Profiles + Cloud Build; gate releases on FPS (p95 >55) and ANR <0.5%. ## Documentation - https://docs.unity3d.com/Manual/TilemapsOverview.html - https://docs.unity3d.com/Packages/com.unity.2d.tilemap.extras@latest - https://docs.unity3d.com/Packages/com.unity.cinemachine@latest - https://docs.unity3d.com/Manual/class-SpriteAtlas.html