Sprint 1 complete: hybrid Compose + LibGDX architecture building

Full AL-001 through AL-008 implementation: shared/ module with ModuleType
enum, GameHost routing, StylusInputBridge, LineCorridorScreen with live
stroke rendering, LineScore (straightness + anglePrecision), score returned
to Compose hub via ActivityResult. Fixes LineScore field mismatch
(pressureConsistency → anglePrecision) caught during AL-009 build check.
Adds .gitignore and handoff notes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ROADMAP.md

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+# ArtLegend Roadmap
+
+---
+
+## Phase 0 — Foundation (current)
+
+**Goal:** Hybrid architecture running end-to-end. Compose hub launches LibGDX game screen with stylus data flowing.
+
+### Milestones
+- [x] LibGDX scaffold (core + android modules)
+- [x] `shared/` module with `ModuleType` enum
+- [x] `GameHost` routing by `ModuleType`
+- [x] `StylusInputBridge` (AtomicReference, thread-safe)
+- [x] `StylusFrame` data class (x, y, pressure, tiltRad, orientRad, isStylus)
+- [x] `MainActivity` + Compose navigation (Hub → Detail → Game)
+- [x] `GameActivity` reads `ModuleType` from Intent, posts stylus frames
+- [x] `LineCorridorScreen` renders guided corridor + real-time stroke
+- [x] Score calculation for Line Corridor (straightness + pressure consistency)
+- [x] Score displayed on return to ModuleDetail (ScoreCard)
+
+---
+
+## Phase 1 — Line Corridor MVP
+
+**Goal:** Shippable first module. Players can train, score, and see improvement over sessions.
+
+### Milestones
+- [ ] Corridor generation (random angle, configurable width)
+- [ ] Stroke capture and rendering (LibGDX ShapeRenderer)
+- [ ] Straightness score algorithm (RMS deviation from ideal line)
+- [ ] Pressure consistency score (variance from target pressure profile)
+- [ ] Difficulty progression (narrowing corridor, longer strokes)
+- [ ] Session summary screen (score + streak)
+- [ ] Local persistence (Room or DataStore) for scores per session
+- [ ] Progress screen populated with real data (last 7 sessions graph)
+
+---
+
+## Phase 2 — Pressure Ramp Module
+
+**Goal:** Second module ships. Shared infrastructure for module scoring is solid.
+
+### Milestones
+- [ ] Pressure Ramp screen: draw a stroke matching a target pressure curve
+- [ ] Pressure curve rendering (target vs actual overlay)
+- [ ] DTW (Dynamic Time Warping) score for pressure curve matching
+- [ ] Unified `ModuleScore` data model shared across modules
+- [ ] Difficulty tiers (linear ramp → S-curve → arbitrary profile)
+
+---
+
+## Phase 3 — Curve Sculptor + Vector Snap
+
+**Goal:** Full 4-module training suite. App is content-complete for v1.0.
+
+### Milestones
+- [ ] Curve Sculptor: hit bezier control points with stylus
+- [ ] Vector Snap: tap precise endpoints within tolerance radius
+- [ ] Per-module difficulty levels stored in settings
+- [ ] Global XP system across all modules
+
+---
+
+## Phase 4 — Monetization Ready
+
+**Goal:** In-app purchase infrastructure. Free tier vs paid modules enforced.
+
+### Milestones
+- [ ] Google Play Billing integration
+- [ ] Entitlement check before launching `GameActivity`
+- [ ] "Line Corridor" free; others gated behind Skill Pack purchase
+- [ ] Pro subscription tier (all modules + cloud sync)
+- [ ] Settings screen: manage subscription, restore purchases
+
+---
+
+## Phase 5 — Cloud + Social
+
+**Goal:** Cross-device sync and community features.
+
+### Milestones
+- [ ] Firebase Auth (Google sign-in)
+- [ ] Firestore sync for scores and progress
+- [ ] Global leaderboard per module
+- [ ] Weekly challenge mode (fixed seed corridor, global rank)
+- [ ] Share score card (image export)
+
+---
+
+## Per-Module Milestones Detail
+
+### Line Corridor
+| Milestone | Description |
+|-----------|-------------|
+| Skeleton | Screen renders, bridge connected |
+| Corridor | Guided corridor drawn, stroke captured |
+| Score | Straightness + pressure score calculated |
+| Persist | Scores saved locally |
+| Polish | Animations, streak counter, SFX |
+
+### Pressure Ramp
+| Milestone | Description |
+|-----------|-------------|
+| Skeleton | Screen renders |
+| Curve target | Target pressure profile displayed |
+| Score | DTW score vs target |
+| Difficulty | 3 difficulty tiers |
+
+### Curve Sculptor
+| Milestone | Description |
+|-----------|-------------|
+| Skeleton | Screen renders |
+| Bezier display | Target bezier curve shown |
+| Stroke eval | How close did the stroke follow the curve? |
+| Control points | Optional control point hints |
+
+### Vector Snap
+| Milestone | Description |
+|-----------|-------------|
+| Skeleton | Screen renders |
+| Target points | Random endpoint targets displayed |
+| Hit detection | Distance from target scored |
+| Speed bonus | Faster accurate taps = higher score |