# CLAUDE.md

## 1. Think Before Coding

**Don't assume. Don't hide confusion. Surface tradeoffs.**

Before implementing:
- State your assumptions explicitly. If uncertain, ask.
- If multiple interpretations exist, present them - don't pick silently.
- If a simpler approach exists, say so. Push back when warranted.
- If something is unclear, stop. Name what's confusing. Ask.

## 2. Simplicity First

**Minimum code that solves the problem. Nothing speculative.**

- No features beyond what was asked.
- No abstractions for single-use code.
- No "flexibility" or "configurability" that wasn't requested.
- No error handling for impossible scenarios.
- If you write 200 lines and it could be 50, rewrite it.

Ask yourself: "Would a senior engineer say this is overcomplicated?" If yes, simplify.

## 3. Surgical Changes

**Touch only what you must. Clean up only your own mess.**

When editing existing code:
- Don't "improve" adjacent code, comments, or formatting.
- Don't refactor things that aren't broken.
- Match existing style, even if you'd do it differently.
- If you notice unrelated dead code, mention it - don't delete it.

When your changes create orphans:
- Remove imports/variables/functions that YOUR changes made unused.
- Don't remove pre-existing dead code unless asked.

The test: Every changed line should trace directly to the user's request.

## 4. Goal-Driven Execution

**Define success criteria. Loop until verified.**

Transform tasks into verifiable goals:
- "Add validation" → "Write tests for invalid inputs, then make them pass"
- "Fix the bug" → "Write a test that reproduces it, then make it pass"
- "Refactor X" → "Ensure tests pass before and after"

For multi-step tasks, state a brief plan:
```
1. [Step] → verify: [check]
2. [Step] → verify: [check]
3. [Step] → verify: [check]
```

Strong success criteria let you loop independently. Weak criteria ("make it work") require constant clarification.

---

## 5. Use PowerShell for Shell Commands

**All shell commands, scripts, rg/fd calls run through pwsh, never cmd or bash.**

- Prefix every shell invocation with `pwsh -Command "..."`
- Example: `pwsh -Command "rg -n 'class' src/"`
- Example: `pwsh -Command "./build.bat"`

## 6. Verify Unity Scripts After Changes

**After modifying `src/CounterDrone.Core/` or `src/Unity/Assets/Scripts/`, run:**

```bash
pwsh scripts/check_unity_build.ps1
```

This automatically rebuilds Core.dll, copies it to Unity Plugins, and compiles Unity scripts. Exits 0 if all pass.

## 7. Run Targeted Tests First

**Always run the narrowest relevant test first.** If you just changed `DefensePlannerTests`, run `--filter 'FullyQualifiedName~DefensePlannerTests'`. If you changed `FullPipelineTests`, run that filter. Don't start with `dotnet test` on the whole project — it wastes time and buries the failures you're looking for.

Run full suite only after the targeted tests pass, to verify nothing else broke.

```bash
# Run a test class:
pwsh -Command "dotnet test test/unit/CounterDrone.Core.Tests/ --filter 'FullyQualifiedName~DefensePlannerTests'"

# Run a single test:
pwsh -Command "dotnet test test/unit/CounterDrone.Core.Tests/ --filter 'FullyQualifiedName~Scenario_AirBased'"

# Run full suite (only after targeted passes):
pwsh -Command "dotnet test test/unit/CounterDrone.Core.Tests/"
```

## 8. No Hardcoded Defaults or Fallbacks

**Every parameter must come from configuration. If a required value is missing, fail explicitly — never silently substitute a default.**

Good:
```csharp
if (unit.CruiseSpeed <= 0)
    throw new InvalidOperationException($"单元 {unit.Id}: CruiseSpeed 必须 > 0");
```

Bad:
```csharp
float speed = unit.CruiseSpeed > 0 ? unit.CruiseSpeed : 55f;  // 55f 是哪来的？
float mv = unit.MuzzleVelocity ?? 800f;                         // 为什么是 800？
float alt = unit.ReleaseAltitude > 0 ? unit.ReleaseAltitude : threat.Altitude + 500f; // 500？
```

This applies to:
- `??` operator with arbitrary numbers (55f, 800f, 1000f, 3, etc.)
- Ternary `> 0 ? x : default` patterns
- `Math.Max(0.1f, x)` to prevent division by zero — instead validate the input before the division
- `if (fireTime < 0.1f) fireTime = 0.1f` — instead skip the event and report the failure

Physics constants (9.81f, 3.6f, π) and documented model parameters (Phase 2 cutoff = 30s) are NOT arbitrary defaults — they are legitimate parts of the physical model.

---

**These guidelines are working if:** fewer unnecessary changes in diffs, fewer rewrites due to overcomplication, and clarifying questions come before implementation rather than after mistakes.
