Phaser Game Development
Build 2D browser games using Phaser 3's scene-based architecture and physics systems.
STOP: Before Loading Any Spritesheet
Read spritesheets-nineslice.md FIRST.
Spritesheet loading is fragile—a few pixels off causes silent corruption that compounds into broken visuals. The reference file contains the mandatory inspection protocol.
Quick rules (details in reference):
- Measure the asset before writing loader code—never guess frame dimensions
- Character sprites use SQUARE frames: If you calculate frameWidth=56, try 56 for height first
- Different animations have different frame sizes: A run cycle needs wider frames than idle; an attack needs extra width for weapon swing. Measure EACH spritesheet independently
- Check for spacing: Gaps between frames require
spacing: Nin loader config - Verify the math:
imageWidth = (frameWidth × cols) + (spacing × (cols - 1))
Reference Files
Read these BEFORE working on the relevant feature:
| When working on... | Read first |
|---|---|
| Loading ANY spritesheet | spritesheets-nineslice.md |
| Nine-slice UI panels | spritesheets-nineslice.md |
| Config, scenes, objects, input, animations | core-patterns.md |
| Tiled tilemaps, collision layers | tilemaps.md |
| Physics tuning, groups, pooling | arcade-physics.md |
| Performance issues, object pooling | performance.md |
Architecture Decisions (Make Early)
Before building, decide:
- What scenes does this game need? (Boot, Menu, Game, UI overlay, GameOver)
- What are the core entities and how do they interact?
- What physics model fits? (Arcade for speed, Matter for realism, None for menus)
- What input methods? (keyboard/gamepad/touch)
Physics System Choice
| System | Use When |
|---|---|
| Arcade | Platformers, shooters, most 2D games. Fast AABB collisions |
| Matter | Physics puzzles, ragdolls, realistic collisions. Slower, more accurate |
| None | Menu scenes, visual novels, card games |
Core Principles
- Scene-first architecture: Organize code around scene lifecycle and transitions
- Composition over inheritance: Build entities from sprite/body/controllers, not deep class trees
- Physics-aware design: Choose collision model early; don't retrofit physics late
- Asset pipeline discipline: Preload everything; reference by keys; keep loading deterministic
- Frame-rate independence: Use
deltafor motion and timers; avoid frame counting
Anti-Patterns
| Anti-Pattern | Problem | Solution |
|---|---|---|
Global state on window | Scene transitions break state | Use scene data, registries |
Loading in create() | Assets not ready when referenced | Load in preload(), use Boot scene |
| Frame counting | Game speed varies with FPS | Use delta / 1000 |
| Matter for simple collisions | Unnecessary complexity | Arcade handles most 2D games |
| One giant scene | Hard to extend | Separate gameplay/UI/menus |
| Magic numbers | Impossible to balance | Config objects, constants |
| No object pooling | GC stutters | Groups with setActive(false) |
Variation Guidance
Outputs should vary based on:
- Genre (platformer vs top-down vs shmup)
- Target platform (mobile touch, desktop keyboard, gamepad)
- Art style (pixel art scaling vs HD smoothing)
- Performance envelope (many sprites → pooling; few sprites → simpler code)
Remember
Phaser provides powerful primitives—scenes, sprites, physics, input—but architecture is your responsibility.
Think in systems: define the scenes, define the entities, define their interactions—then implement.
Codex can build complete, polished Phaser games. These guidelines illuminate the path—they don't fence it.