# Scenario Unity 2D

> Use when building a 2D game in Unity 6.3 URP: pixel-art or HD sprite import and PPU, sprite atlas…

Use when building a 2D game in Unity 6.3 URP: pixel-art or HD sprite import and PPU, sprite atlases, Tilemaps, Rule Tiles and reskins, the 2D Renderer and 2D lights with normal maps, 2D animation, a platformer or top-down controller ("make a platformer controller that feels good", coyote time, jump buffer, one-way platforms, spikes), Pixel Perfect Camera, a follow or room camera, hit stop and screen shake; or when pixel art looks blurry or shimmers, tiles show seams, 2D lights do nothing or cost too much, the jump feels floaty, or the camera loses the player when falling.

- Page: https://ss33.ai/skills/scenario-labs/scenario-unity-2d-27210174978
- Publisher: scenario-labs
- Category: [Software Development](https://ss33.ai/skills/category/software-development-t44z8z) › [Misc](https://ss33.ai/skills/category/software-development-t44z8z/misc-0pfo0b)
- License: MIT
- Source: https://github.com/scenario-labs/skills/blob/ccc6c5c623a4f96423df0d157b8ef174f14edfd8/skills/game-engines/unity/scenario-unity-2d/SKILL.md

## Skill

SKILL.md: https://ss33.ai/api/v1/ss33/download/scenario-labs/scenario-unity-2d-27210174978

# Unity 2D (developer and artist)

Expert 2D work in Unity 6.3 is a chain of coupled settings proven by numbers and a frame: one PPU
from art to camera, atlases judged by what they save, tiles and lights authored as data and costed,
a camera that moves in whole pixels, and a controller whose feel is measured, not asserted.
Everything below was run in Unity 6000.3.21f1 through batch jobs and PlayMode tests
([`references/procedures.md`](references/procedures.md)). If a sibling skill named here is missing
from your available skills, ask the user to install it
(`npx skills add scenario-labs/skills --skill <name>`); unattended, proceed from tool schemas and
flag the gap.

**REQUIRED BACKGROUND:** scenario-unity-expert (channels, review loop, 6.3 traps).

## Stance (the expert delta)

1. **Pixel perfect is a pipeline, and URP already ships the camera.** One PPU on every sprite (tile
   px = 1 unit), Point, Compression None, whole-pixel pivots, Assets PPU = sprite PPU. Never install
   `com.unity.2d.pixel-perfect` in URP: it is the Built-in component (6.3 Manual). Measured: 100%
   uniform 6 x 6 blocks at 1080p.
2. **Pick Grid Snapping by what must be pixelated, and judge pixels in motion.** Pixel Snapping
   snaps sprites only; lights, bloom, particles stay at screen resolution (2qeNu2QApAM [00:01:47]);
   Upscale Render Texture pixelates everything. Retro AA vs Point is shimmer vs blur (Manual), and
   in URP 17.3 it only acts under Stretch Fill. Measured over a sub-pixel pan: integer framing moves
   in whole art pixels (rigid 0.9997); Stretch Fill Point leaves 0.6% of pixels shimmering per
   frame, Retro AA 0.3% at twice the softness; no Pixel Perfect Camera, 2.8%.
3. **Under the SRP Batcher an atlas cuts textures, not Batches or SetPass.** Measured 21/21 batches,
   2/2 SetPass, bound textures 20 to 1 (Unity hXlpnwD-TgY [00:05:55], [00:07:32]); memory only drops
   when usage is high. Compress once, on the atlas, except pixel-art pages stay None: compression
   shifts pixel colors (2qeNu2QApAM [00:02:24]). `AuditAtlases` reproduces the 6.3 Sprite Atlas
   Analyzer reports plus Read/Write; grouping by co-visibility is the step no tool does.
4. **The controller owns the velocity; forgiveness is design, each trick behind a toggle.** Latch
   input in Update; collisions, jump, horizontal, gravity, apply in FixedUpdate; coyote and buffer
   are timestamp windows (Tarodev source). "Working on the player's intent" (Thorson, GMTK
   yorTG9at90g [00:11:03]), so coyote, buffer, variable jump, fall clamp, apex hang and corner
   correction each get an on/off toggle for A/B play (Tarodev 3sWTzMsmdx8 [00:02:24]), and hazard
   hitboxes are smaller than the art (GMTK [00:09:28]). Two choices are feel decisions, never
   defaults: the **variable-height method** (velocity cut 50% precise, gravity x3 smooth, sustain
   while held long; Dawnosaur 2S3g8CgBG1g [00:00:36]) and the **air friction** (Tarodev
   AirDeceleration 30 drifts 3.1 units, 5.7 body widths, after release; Celeste's "massive air
   friction" drops almost straight down, GMTK [00:04:14]; 240 stops in 3 steps).
5. **Lights are routed by sorting layers and paid per light batch.** Consecutive sorting layers
   share a light batch only if every visible light lights both or neither, and the normal, shadow
   and light passes run once per batch (URP 17.3 source). A player fill light that skips the
   Characters layer (Sasquatch 1h-hSlffawM [00:01:35]) split the demo level from 1 batch into 4 and
   light fill from 0.99 to 3.64 screens. Cost is fill rate (e-book p. 131): bench at 4K over 6 runs,
   shadows x5.4 to x5.9, the batch split +72 to +101%, normal maps +15 to +36%, large vs small
   lights +8 to +43% (noisy). Never a pitch-black area (Global 0.25, GDC YhrwKF_i-BI [00:11:43]);
   enable normal maps on the light (GDC [00:12:31]); Fast on low tiers.
6. **Sprite animation never blends and follows the controller.** Exit time off, duration 0, Any
   State self-transition off; parameters from what the controller did, not from input (Brackeys
   hkaysu1Z-N8 [00:16:17], [00:18:57]).
7. **The camera and the juice are part of feel.** Loose vertical damping rising, tight once falling
   past a speed threshold, back at vertical speed 0 (hysteresis), lerped (Sasquatch 9dzBrLUIF8g
   [00:05:37], [00:07:14]): in a 40-unit drop a fixed 0.6 s damping let the feet reach the bottom
   edge, the switch kept 3.2 to 3.4 units below in view. Swap room cameras on trigger EXIT by exit
   direction ([00:14:43]); bounds end exactly at a secret room ([00:02:10]). Hit stop 20 ms (Nijman
   AJdEqssNZ-U [00:18:22]) to 67 ms (Celeste, GMTK [00:08:40]) on unscaled time, extend not stack;
   shake with an off option (Nijman [00:32:14]).
8. **Be honest about GUI-only editors.** Tile Palette, Rule Tile inspector, AutoTile masks, Sprite
   Editor, Skinning Editor and the Animator window are mouse tools. Agents author through
   `Tilemap.SetTiles`, `RuleTile.m_TilingRules`, `RuleOverrideTile.ApplyOverrides`,
   `ISpriteEditorDataProvider`, `AnimatorController`; rigging and AutoTile masks stay human
   ([`references/gui-paths.md`](references/gui-paths.md)).

## Establish first

Ask once: pixel art or HD (defaults: pixel, 16 PPU, 320 x 180); target screens including 21:9 and
phones; camera model (static rooms, follow with bias and fall damping, lead toward action);
real-time 2D lights or painted light, and the lowest tier; controller profile (precision: own the
velocity, high air friction; momentum: low air friction; physics-rich: Dynamic body with forces;
top-down: velocity); jump height in tiles and the variable-height method; hazards and one-way
platforms; input devices. Then `ut_2d.project(P)`.

## Workflow

1. **Project.** `TwoDSetup.ProjectSetup`: sorting layers back to front (few: they drive light
   batching), Player and Ground layers. GATE: order read back, no pixel-perfect package, Input
   System, fixed step 0.02 s.
2. **Import.** `SpriteJobs.ImportPixelArt` (slicing, pixel pivots, `_NormalMap`) or `ImportHD` (PPU
   = height / (2 x ortho), e-book p. 21); shaped tiles get `SetPhysicsOutline` (16 px sprites
   generate a 4-point rectangle). GATE: `AuditSprites` 0 errors; one PPU.
3. **Atlases.** `AtlasJobs.BuildAtlas` per co-visible group, lit and plain apart, pixel pages
   uncompressed. GATE: 1 page, 0 findings, grouping rule written.
4. **Level.** `TilemapJobs.CreateRuleTile` + `BuildLevel`; reskins with `CreateRuleOverrideTile`;
   Composite Merge, Outlines, Static; per-tile colliders only for runtime edits, then Use Delaunay
   Mesh. GATE: `rule_mismatches == 0` (reskin read-back too), drop probe within 0.05 units, capture
   shows no seams.
5. **Actors and animation.** `AnimJobs.BuildSpriteAnimator`, `LevelJobs.Populate` (player,
   `Hazard2D` spikes with inset hitboxes, one-way platforms). GATE: `LintAnimator` 0 errors;
   hitbox-to-art ratios below 1.
6. **Lights.** `LightJobs.LightRig`, then `LightJobs.LightCost` (tier; engine check once the camera
   exists). GATE: `Audit2D` 0 errors; replica light batches = URP's own count; every batch break and
   every light over half the view justified; normals on/off capture pair differs.
7. **Camera.** `CameraJobs.SetupPixelPerfect`, `CapturePixelPerfect`; a sub-pixel pan
   (`ut_2d.pan_shots`) scored by `ut_2d.shimmer_check`; follow cameras through
   `CinemachineJobs.Setup` (CM 3.1.7 pinned) plus `CinemachineFallDamping` and
   `CinemachineRoomSwap`. GATE: `pixel_block_check` >= 0.999 at 1080p and 720p, pan min rigid >=
   0.99, `void_columns` 0 at 21:9, `bounds_hide_secrets` ok, contact sheet looked at.
8. **Feel.** PlayMode tests with simulated input (`ut_run.run_tests(P, "PlayMode", graphics=True)`).
   GATE: apex = 50 Hz prediction, windows within one step, one press = one jump at 30/60/144 fps,
   each toggle A/B, method and air-drift numbers stated. Feel itself is a human verdict: ship
   toggles and numbers.
9. **Deliver.** `Audit2D.Scene` clean; `AgentProfile.PlayModeTimings` budget pass; report each step
   with its Unity call, then Verified and Assumed.

## Numbers

| Value                                                                                                                                 | Relative to                | Source                         |
| ------------------------------------------------------------------------------------------------------------------------------------- | -------------------------- | ------------------------------ |
| PPU = H / (2 x ortho size): 216 at 4K Size 5                                                                                          | HD art, closest zoom       | e-book p. 21                   |
| 320 x 180: x4 720p, x6 1080p, x8 1440p, x12 4K; ortho 5.625 at 16 PPU                                                                 | pixel reference            | Manual; [added] arithmetic     |
| MaxSpeed 14, Accel 120, GroundDecel 60, AirDecel 30, JumpPower 36, FallAccel 110, MaxFall 40, release x3, Coyote 0.15 s, Buffer 0.2 s | Tarodev stats (u/s, u/s^2) | Tarodev repo                   |
| apex 5.536 at 50 Hz (formula 5.89), rise 0.32 s; tap: gravity x3 2.08, cut 0.5 1.81, sustain (JumpPower 18.7) 1.78 of 5.52            | those stats                | measured, replay               |
| air drift after release at top speed: AirDecel 30 3.13 units (24 steps), 240 0.27 (3 steps)                                           | 0.55-unit body             | measured                       |
| Celeste: about 6 frames to top speed, 3 to stop, jump about 3 body heights (Mario 4, Meat Boy 6)                                      | 60 fps frames              | GMTK [00:02:01], [00:03:42]    |
| apex band gravity x0.5 below 5 u/s held (+0.08 s); corner nudge 0.25 units                                                            | added tricks               | Dawnosaur [00:02:06]; [added]  |
| hazard hitbox inset 2 px sides, 3 px top: 0.75 x 0.625 of a 16 x 8 spike                                                              | art                        | [added] values                 |
| fall damping 0.6 s loose, 0.1 s tight, switch below -15 u/s, back at 0, 0.2 s blend                                                   | follow camera              | [added] values; rule Sasquatch |
| hit stop 0.02 to 0.07 s                                                                                                               | real time                  | Nijman; GMTK                   |
| Global light 0.25; light render scale 0.5 (template)                                                                                  | lighting                   | GDC; observed                  |
| one atlas page; wastage flag > 400 KB                                                                                                 | per atlas                  | hXlpnwD-TgY                    |
| 12 samples per second for sprite clips                                                                                                | frame-by-frame             | Brackeys [00:03:42]            |

## Quality gates

- **Measurable:** audits at 0 errors (`AuditSprites`, `AuditAtlases`, `Audit2D`, `LintAnimator`);
  `rule_mismatches == 0`; drop probe < 0.05; `pixel_block_check` >= 0.999; pan rigid >= 0.99;
  `void_columns` 0 at 21:9; light batches replica = engine; PlayMode suite 0 failures; frame budget
  pass with `ut_stat.summarize_csv`.
- **Visual:** every capture through `ut_review.review_images` and a contact sheet you open, 2x crops
  for pixel edges; lighting pair; `critique.md` sections A to H.

## Common mistakes

| Mistake                                                         | What it looks like                                     | Fix                                                                         |
| --------------------------------------------------------------- | ------------------------------------------------------ | --------------------------------------------------------------------------- |
| 2D Pixel Perfect package in URP                                 | wrong component, settings ignored                      | URP `PixelPerfectCamera`                                                    |
| PPU per sprite, Bilinear, compressed                            | blur, color shift, uneven pixels                       | ImportPixelArt + AuditSprites                                               |
| shimmer judged on stills                                        | crisp frames, crawling pixels in motion                | `pan_shots` + `shimmer_check`; integer Crop Frame                           |
| batch capture right after OpenScene                             | only the Global light shows                            | `CameraJobs.WarmLights2D`                                                   |
| Light2D added by script                                         | shadows on, normals off (`normalMapQuality` read-only) | set both; SerializedObject `m_NormalMapQuality`                             |
| a light skipping one sorting layer                              | light batches split, every light redrawn               | same Target Sorting Layers where the look allows; `LightCost`               |
| Accurate normals, big lights, many shadows on mobile            | fill-rate bound frame                                  | Fast, smaller lights, 1 to 2 shadow lights                                  |
| atlas judged by Batches or SetPass                              | "atlas does nothing"                                   | used textures and memory                                                    |
| compressed pixel-art atlas page                                 | color shifts in flat pixels                            | Compression None on pixel pages                                             |
| `_timeJumpWasPressed = 0` (Tarodev)                             | phantom jump on first landing                          | `float.MinValue`                                                            |
| input read in FixedUpdate                                       | lost presses at high fps                               | latch in Update                                                             |
| ground and ceiling casts that hit triggers or one-way platforms | "grounded" on a trigger, head bonks under a platform   | `useTriggers = false`; skip one-way colliders (as `PlatformerController2D`) |
| one AirDeceleration for every game                              | slides off small platforms, or no momentum             | choose by level; state the drift                                            |
| hazard hitbox = art                                             | death on a 1 px graze                                  | `Hazard2D.FitHitbox` inset                                                  |
| Rotated rule transform on ground                                | grass on walls                                         | Fixed or MirrorX                                                            |
| duplicated Rule Tile for a reskin                               | rule fixes applied twice or missed                     | Rule Override Tile                                                          |
| blended sprite transitions                                      | late, smeared switches                                 | exit time off, duration 0                                                   |
| fixed vertical damping on a follow camera                       | player falls out of the frame                          | `CinemachineFallDamping`                                                    |
| room swap on trigger enter                                      | wrong camera when the player turns back                | swap on exit by direction                                                   |
| legacy `Input.GetAxis`                                          | runtime exception (templates)                          | Input System actions                                                        |

## Handoffs

- **Receives:** sprites and tiles from scenario-game-assets, scenario-sprite-pipeline,
  scenario-textures (PNG, intended PPU, palette); input actions from scenario-unity-architecture;
  the pipeline asset from scenario-unity-rendering-lighting.
- **Delivers:** Cinemachine 3 rigs to scenario-unity-animation (bounds, ortho, pixel ratio, fall
  damping, room swaps); Sprite Custom Lit and Sort 3D as 2D shaders to scenario-unity-shaders;
  pixel-grid particles to scenario-unity-vfx; light batches, fill and bench numbers to
  scenario-unity-performance; texture formats to scenario-unity-mobile; Web size to
  scenario-unity-web; postprocessors and CI runs to scenario-unity-pipeline-automation; HUD to
  scenario-unity-ui; non-platformer physics to scenario-unity-gameplay. Every packet carries job
  ids, audit counts, PlayMode metrics and contact sheets.

## Unity 6.3 notes

- `UnityEngine.Rendering.Universal.PixelPerfectCamera` (URP 17.3): Grid Snapping dropdown; Filter
  Mode has no public setter; the camera position is rounded to the pixel grid before every render.
- Universal 2D template: Input System only, Sprite Atlas V2, 2D Tooling 1.0.3 (Window > Analysis >
  Sprite Atlas Analyzer), Tilemap Extras 6.0.2 (AutoTile masks: no public API), 2D Animation 13.0.5,
  SRP Batcher on. Window > 2D > Light Batching Debugger shows the light batches `LightCost`
  computes.
- `Rigidbody2D.linearVelocity`, `bodyType`; `Physics2D.autoSyncTransforms` obsolete;
  LowLevelPhysics2D renamed PhysicsCore2D in 6.5.
- 3D in 2D: Mesh2D-Lit-Default and Sort 3D as 2D; 2D lights reach meshes through a Sorting Group.
- Cinemachine defaults to 2.10.7: pin `com.unity.cinemachine` 3.1.7; core in 6.6. Runtime atlases
  arrive in 6.4; PVRTC removed in 6.4.

## References

- `references/procedures.md`: procedures P0 to P14, Unity APIs, live tests, measured results.
- [`references/expert-notes.md`](references/expert-notes.md): principles by expert, timestamps,
  deciding conditions.
- [`references/critique.md`](references/critique.md): the rubric (import, atlases, tiles, lights,
  camera, feel, animation and juice, report).
- `references/gui-paths.md`: windows and menus for the same work.
- [`references/sources.md`](references/sources.md): sources, credentials, timestamps, revision
  history.
- [`scripts/ut_2d.py`](scripts/ut_2d.py): install, resolution and feel math (jump methods, air
  drift), art generators, `pixel_block_check`, `shimmer_check`, `void_columns`,
  `bounds_hide_secrets`, metrics.
- [`scripts/AgentKit/TwoD/`](scripts/AgentKit/TwoD/): editor jobs (setup, sprites, atlases,
  tilemaps, level, lights and light cost, camera, Cinemachine, animation, audit, LowLevelPhysics2D).
- [`scripts/Runtime/TwoD/`](scripts/Runtime/TwoD/): `PlatformerController2D`, `PlatformerStats`,
  `Hazard2D`, `FallDampingSwitch`, `PlatformerAnimatorBridge`, `HitStop`, `CameraShake2D`,
  `TopDownMover2D`; [`scripts/Runtime/TwoDCinemachine/`](scripts/Runtime/TwoDCinemachine/):
  `Cinemachine2DRig`, `CinemachineFallDamping`, `CinemachineRoomSwap` (compile only with CM3).