# Phase 1: Foundation - Context

**Gathered:** 2026-03-10
**Status:** Ready for planning

<domain>
## Phase Boundary

Build the technical foundation: game loop, HiDPI-aware canvas rendering, Player 1 keyboard input (W/S), ball physics (continuous movement, wall bouncing, zone-based angle deflection, per-hit speed increase). No scoring, no AI, no UI screens yet.

</domain>

<decisions>
## Implementation Decisions

### File Structure
- Single HTML file — everything embedded (JS + CSS in one `.html` file)
- JavaScript organized into a module pattern: `GameLoop`, `Physics`, `Renderer`, `Input` objects within a single `<script>` tag
- No build tooling; runs directly from the filesystem

### Canvas Sizing
- Full-window canvas — fills the entire browser window
- Resizes immediately on window resize
- Maintains aspect ratio during resize; minimum 4:3 aspect ratio enforced
- No maximum size cap — grows unbounded to fill any screen
- Must be HiDPI/Retina aware (devicePixelRatio scaling)

### Ball Physics Feel
- Zone-based deflection: paddle divided into 5 zones
  - Top edge → ~60° angle upward
  - Upper zone → ~30° angle
  - Center → ~5° angle (nearly flat)
  - Lower zone → ~30° angle
  - Bottom edge → ~60° angle downward
- Speed increases per paddle hit (small increment each rally)
- Speed resets on each point scored
- No maximum speed cap — ball accelerates indefinitely through long rallies

### Claude's Discretion
- Exact speed increment value per hit (tune for feel)
- Precise zone boundary definitions and angle values (within the ~5°–60° range)
- Game loop timing implementation (requestAnimationFrame + delta time)
- Serve direction and initial ball velocity for dev testing
- Input handling internals (keydown/keyup state tracking)

</decisions>

<specifics>
## Specific Ideas

- No specific requirements — open to standard approaches

</specifics>

<code_context>
## Existing Code Insights

### Reusable Assets
- None — fresh project, no existing code

### Established Patterns
- None yet — Phase 1 establishes the patterns all subsequent phases follow

### Integration Points
- Phase 2 will add scoring, Player 2 input, and AI — the game loop and physics module must be structured to accommodate adding a second paddle and score tracking without refactoring

</code_context>

<deferred>
## Deferred Ideas

- None — discussion stayed within phase scope

</deferred>

---

*Phase: 01-foundation*
*Context gathered: 2026-03-10*