feat: Method B TGC+FP필터, Placement UI 리디자인, 네비게이션 개선

Method B 알고리즘 (Python 동기화):
- TGC 파이프라인: applyTgc (감쇠 보상, adaptive ratio)
- 후면반사 제거: findBackReflectionIdx + suppressBackReflection
- 멀티채널 합의: findBackReflectionMultichannel (median)
- FP 필터: wallMin/lowMean < 1.15, score < 3000
- peakMin: max(lowMean+margin, threshold)
- Otsu: separability 반환 + OTSU_RATIO(0.85) + fallback(sep<0.3)
- urineLen: post-ant → post-ant-1 (Python 동기화)
- ant fallback: span 시작 직전 (단조 감소 대응)

Placement UI 리디자인:
- 상반신 일러스트 (Canvas: 몸통+배꼽+치골+방광+센서+화살표)
- Green Zone: 배경 animateColorAsState 전환 + 체크마크
- 가이드 순서: 치골→위로→CH0 안잡히면 아래로→좌우 대칭
- 디바운스 4초 유지, 힌트 텍스트 Green시 초록
- 좌우 힌트: CH4/CH5 비교 기반 방향 제시
- 설정 톱니바퀴 + floating 패널 (Method A/B/C + Otsu)
- 채널 dot row 별도 배치
- Green score: CV 0.10, LR dev 0.25 (엄격화)

도넛차트 UI:
- Max Vol 카드 제거 (4→3칸), InfoCard 높이 통일
- Void/Catheterize 버튼 (2줄, 56dp)
- Quick Save: 실제 측정값 표시 + volume 0 리셋
- 기본 Method C

네비게이션:
- Placement 뒤로가기 → 연결중이면 Monitoring (Home 안감)
- Home Start → 연결중이면 바로 Monitoring (DeviceScan 스킵)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/main/java/com/example/medilightv2android/AppState.kt

@@ -95,7 +95,7 @@ class AppState(private val context: Context) {
     fun startFromHome() {
         sensorMode = SensorMode.PIEZO
         storage.sensorMode = SensorMode.PIEZO
-        currentScreen = AppScreen.DEVICE_SCAN
+        currentScreen = if (isDeviceConnected) AppScreen.PIEZO_MONITORING else AppScreen.DEVICE_SCAN
     }
 
     fun selectSensor(mode: SensorMode) {

app/src/main/java/com/example/medilightv2android/MainActivity.kt

@@ -68,7 +68,7 @@ fun MedilightApp(modifier: Modifier = Modifier) {
             // 메인 플로우: Home → DeviceScan → Personalization → Placement → Monitoring
             AppScreen.DEVICE_SCAN -> appState.currentScreen = AppScreen.HOME
             AppScreen.PIEZO_PERSONALIZATION -> appState.currentScreen = AppScreen.DEVICE_SCAN
-            AppScreen.PLACEMENT_GUIDE -> appState.currentScreen = AppScreen.PIEZO_PERSONALIZATION
+            AppScreen.PLACEMENT_GUIDE -> appState.currentScreen = if (appState.isDeviceConnected) AppScreen.PIEZO_MONITORING else AppScreen.HOME
             AppScreen.PIEZO_MONITORING -> appState.currentScreen = AppScreen.PLACEMENT_GUIDE
             // 모니터링 하위 화면 → 모니터링
             AppScreen.MEASUREMENT_HISTORY -> appState.currentScreen = AppScreen.PIEZO_MONITORING

app/src/main/java/com/example/medilightv2android/managers/GreenZoneConstants.kt

@@ -16,7 +16,7 @@ enum class DetectionMethod { METHOD_A, METHOD_B, METHOD_C }
 
 object GreenZoneConstants {
 
-    var detectionMethod: DetectionMethod = DetectionMethod.METHOD_B
+    var detectionMethod: DetectionMethod = DetectionMethod.METHOD_C
 
     // ═══════════════════════════════════════════════════════════
     // 신호 범위

app/src/main/java/com/example/medilightv2android/managers/PiezoEchoAnalyzer.kt

@@ -157,6 +157,32 @@ class PiezoEchoAnalyzer private constructor() {
         }
     }
 
+    /** 다채널 TGC 파이프라인: denoise → TGC → findBackReflection → suppress → detect */
+    fun analyzeMultiChannelWithTgc(channelData: List<PiezoChannelData>): List<ChannelAnalysisResult> {
+        // 1) SG denoise all channels
+        val raws = channelData.map { DoubleArray(it.buffer.size) { i -> it.buffer[i].toDouble() } }
+        val denoised = raws.map { denoise(it) }
+
+        // 2) TGC per channel
+        val tgcSignals = denoised.map { applyTgc(it) }
+
+        // 3) Multi-channel back reflection consensus
+        val brIdx = findBackReflectionMultichannel(tgcSignals, postMaxIdx)
+
+        // 4) Per-channel: suppress → detect
+        return channelData.mapIndexed { idx, ch ->
+            try {
+                val raw = raws[idx]
+                val sg = denoised[idx]
+                val cleaned = suppressBackReflection(sg, brIdx)
+                val result = detectLowEcho(raw = raw, denoised = cleaned, otsuSignal = sg, dynamicPostMax = brIdx)
+                ChannelAnalysisResult(ch.channel, result, raw, cleaned)
+            } catch (_: Exception) {
+                ChannelAnalysisResult(ch.channel, null, raws[idx], denoised[idx])
+            }
+        }
+    }
+
     /** 다채널 분석 → 최종 용적 */
     fun analyzeMultiChannel(channelData: List<PiezoChannelData>): PiezoAnalysisResult {
         val results = channelData.map { ch ->
@@ -313,38 +339,140 @@ class PiezoEchoAnalyzer private constructor() {
 
     var useAdaptiveThreshold: Boolean = true
     var lastOtsuThreshold: Double = 0.0; private set
+    var lastOtsuSeparability: Double = 0.0; private set
 
-    /** 단일 1D 채널 → urine region 탐지 */
-    fun detectLowEcho(raw: DoubleArray, denoised: DoubleArray): LowEchoResult? {
+    // Otsu 관련 상수
+    val otsuRatio: Double = 0.85
+    val minOtsuSeparability: Double = 0.3
+    val minScore: Double = 3000.0
+    val wallLowMeanMinRatio: Double = 1.15
+
+    /** 단일 1D 채널 → urine region 탐지 (otsuSignal: suppress 전 원본 SG로 Otsu 계산) */
+    fun detectLowEcho(raw: DoubleArray, denoised: DoubleArray, otsuSignal: DoubleArray? = null, dynamicPostMax: Int? = null): LowEchoResult? {
         val sg = denoised
         if (sg.size < 10) return null
 
-        val thr = if (useAdaptiveThreshold) {
-            val limit = min(sg.size, postMaxIdx + 1)
-            otsu1d(sg, limit)
-        } else {
-            lowEchoAmpDefault
+        val effectivePostMax = dynamicPostMax ?: postMaxIdx
+
+        if (!useAdaptiveThreshold) {
+            lastOtsuThreshold = lowEchoAmpDefault
+            lastOtsuSeparability = 0.0
+            return detectLowEchoCore(sg = sg, threshold = lowEchoAmpDefault, effectivePostMax = effectivePostMax)
         }
-        lastOtsuThreshold = thr
-        return detectLowEchoCore(sg = sg, threshold = thr)
+
+        val otsuInput = otsuSignal ?: sg
+        val limit = min(otsuInput.size, effectivePostMax + 1)
+        val (thr, sep) = otsu1dWithSeparability(otsuInput, limit)
+        val adjustedThr = thr * otsuRatio
+        lastOtsuSeparability = sep
+
+        if (sep >= minOtsuSeparability) {
+            lastOtsuThreshold = adjustedThr
+            return detectLowEchoCore(sg = sg, threshold = adjustedThr, effectivePostMax = effectivePostMax)
+        }
+
+        // Separability 낮음 → 고정 threshold fallback
+        lastOtsuThreshold = lowEchoAmpDefault
+        return detectLowEchoCore(sg = sg, threshold = lowEchoAmpDefault, effectivePostMax = effectivePostMax)
+    }
+
+    // ── TGC (Time Gain Compensation) ──
+
+    fun applyTgc(signal: DoubleArray): DoubleArray {
+        val n = signal.size
+        if (n < 5) return signal.copyOf()
+
+        val x = DoubleArray(n) { it.toDouble() }
+        // Linear fit: slope, intercept
+        var sumX = 0.0; var sumY = 0.0; var sumXY = 0.0; var sumX2 = 0.0
+        for (i in 0 until n) { sumX += x[i]; sumY += signal[i]; sumXY += x[i] * signal[i]; sumX2 += x[i] * x[i] }
+        val slope = (n * sumXY - sumX * sumY) / (n * sumX2 - sumX * sumX)
+
+        if (slope >= 0) return signal.copyOf() // 감쇠 없으면 보상 불필요
+
+        val absSlope = abs(slope)
+        val slopeThresh = 3.0; val slopeMax = 15.0; val ratioMin = 0.1
+        val ratio = if (absSlope < slopeThresh) 1.0
+        else max(ratioMin, 1.0 - (1.0 - ratioMin) * (absSlope - slopeThresh) / (slopeMax - slopeThresh))
+
+        val targetSlope = slope * ratio
+        val compensation = DoubleArray(n) { (targetSlope - slope) * x[it] }
+        return DoubleArray(n) { signal[it] + compensation[it] }
+    }
+
+    // ── Back Reflection Detection & Suppression ──
+
+    fun findBackReflectionIdx(tgcSg: DoubleArray, postMaxIdx: Int, minSearchIdx: Int = 40, extend: Int = 20): Int {
+        val n = tgcSg.size
+        val searchEnd = min(n, postMaxIdx + extend)
+        if (minSearchIdx >= searchEnd) return postMaxIdx
+
+        val seg = tgcSg.sliceArray(minSearchIdx until searchEnd)
+        val peaks = findPeaks1D(seg)
+        if (peaks.isEmpty()) return postMaxIdx
+
+        val globalPeaks = peaks.map { it + minSearchIdx }
+        return globalPeaks.maxByOrNull { tgcSg[it] } ?: postMaxIdx
+    }
+
+    fun suppressBackReflection(sg: DoubleArray, backRefIdx: Int, searchMargin: Int = 10): DoubleArray {
+        val cleaned = sg.copyOf()
+        val n = sg.size
+        if (backRefIdx >= n) return cleaned
+
+        val lo = max(0, backRefIdx - min(searchMargin, 3))
+        val hi = min(n, backRefIdx + searchMargin + 1)
+        var actualPeak = lo
+        for (i in lo until hi) if (sg[i] > sg[actualPeak]) actualPeak = i
+
+        // left valley
+        val valleyLoStart = max(0, actualPeak - searchMargin)
+        var leftValley = valleyLoStart
+        for (i in valleyLoStart..actualPeak) if (sg[i] < sg[leftValley]) leftValley = i
+
+        // right valley
+        val valleyHiEnd = min(n, actualPeak + searchMargin + 1)
+        var rightValley = actualPeak
+        for (i in actualPeak until valleyHiEnd) if (sg[i] < sg[rightValley]) rightValley = i
+
+        if (rightValley > leftValley) {
+            val leftVal = sg[leftValley]
+            val rightVal = sg[rightValley]
+            val length = rightValley - leftValley
+            for (i in 0..length) {
+                cleaned[leftValley + i] = leftVal + (rightVal - leftVal) * i.toDouble() / length
+            }
+        }
+        return cleaned
+    }
+
+    /** 다채널 후면 반사 위치 합의 (median) */
+    fun findBackReflectionMultichannel(tgcSignals: List<DoubleArray>, postMaxIdx: Int): Int {
+        val detected = mutableListOf<Int>()
+        for (tgc in tgcSignals) {
+            val idx = findBackReflectionIdx(tgc, postMaxIdx)
+            if (idx < postMaxIdx) detected.add(idx)
+        }
+        if (detected.isEmpty()) return postMaxIdx
+        detected.sort()
+        return detected[detected.size / 2]
     }
 
     /**
-     * 1D Otsu threshold — 원은지 연구원 span_utils.py otsu_1d() 1:1 포팅
-     *
-     * 히스토그램에서 between-class variance를 최대화하는 임계값 반환.
-     * 저진폭(urine/조직)과 고진폭(벽 echo) 두 모집단을 분리.
+     * 1D Otsu threshold + separability
      */
-    fun otsu1d(values: DoubleArray, limit: Int = values.size, nBins: Int = 64): Double {
+    data class OtsuResult(val threshold: Double, val separability: Double)
+
+    fun otsu1dWithSeparability(values: DoubleArray, limit: Int = values.size, nBins: Int = 64): OtsuResult {
         val n = min(values.size, limit)
-        if (n == 0) return 0.0
+        if (n == 0) return OtsuResult(0.0, 0.0)
 
         var vMin = values[0]; var vMax = values[0]
         for (i in 1 until n) {
             if (values[i] < vMin) vMin = values[i]
             if (values[i] > vMax) vMax = values[i]
         }
-        if (vMax == vMin) return vMin
+        if (vMax == vMin) return OtsuResult(vMin, 0.0)
 
         val binWidth = (vMax - vMin) / nBins
         val hist = IntArray(nBins)
@@ -355,24 +483,21 @@ class PiezoEchoAnalyzer private constructor() {
 
         val centers = DoubleArray(nBins) { vMin + (it + 0.5) * binWidth }
         val total = n.toDouble()
+        val p = DoubleArray(nBins) { hist[it] / total }
 
-        // cumulative probability & mean
         val cumP = DoubleArray(nBins)
         val cumMP = DoubleArray(nBins)
-        cumP[0] = hist[0] / total
-        cumMP[0] = cumP[0] * centers[0]
+        cumP[0] = p[0]; cumMP[0] = p[0] * centers[0]
         for (i in 1 until nBins) {
-            cumP[i] = cumP[i - 1] + hist[i] / total
-            cumMP[i] = cumMP[i - 1] + (hist[i] / total) * centers[i]
+            cumP[i] = cumP[i - 1] + p[i]
+            cumMP[i] = cumMP[i - 1] + p[i] * centers[i]
         }
         val totalM = cumMP[nBins - 1]
 
-        // between-class variance 최대화
         var bestSigma = -1.0
         var bestIdx = 0
         for (t in 0 until nBins - 1) {
-            val w0 = cumP[t]
-            val w1 = 1.0 - w0
+            val w0 = cumP[t]; val w1 = 1.0 - w0
             if (w0 < 1e-6 || w1 < 1e-6) continue
             val m0 = cumMP[t] / w0
             val m1 = (totalM - cumMP[t]) / w1
@@ -382,18 +507,26 @@ class PiezoEchoAnalyzer private constructor() {
                 bestIdx = t
             }
         }
-        return centers[bestIdx]
+        // Separability: σ_b² / σ_total²
+        var totalVar = 0.0
+        for (i in 0 until nBins) totalVar += p[i] * (centers[i] - totalM) * (centers[i] - totalM)
+        val separability = if (totalVar > 1e-12) bestSigma / totalVar else 0.0
+
+        return OtsuResult(centers[bestIdx], separability)
+    }
+
+    fun otsu1d(values: DoubleArray, limit: Int = values.size, nBins: Int = 64): Double {
+        return otsu1dWithSeparability(values, limit, nBins).threshold
     }
 
     /**
-     * Low-echo 탐지 핵심 — prominence 기반 wall peak 선택
-     * 1:1 port of low_echo_detection_method_b.py (2026-04-20 update)
+     * Low-echo 탐지 핵심 — prominence 기반 wall peak 선택 + FP 필터
      */
-    private fun detectLowEchoCore(sg: DoubleArray, threshold: Double): LowEchoResult? {
+    private fun detectLowEchoCore(sg: DoubleArray, threshold: Double, effectivePostMax: Int = postMaxIdx): LowEchoResult? {
         if (sg.size < 10) return null
 
-        // 1) low-echo span 추출 (postMaxIdx까지만 — 이후는 노이즈)
-        val analysisLimit = min(sg.size, postMaxIdx + 1)
+        // 1) low-echo span 추출 (effectivePostMax까지)
+        val analysisLimit = min(sg.size, effectivePostMax + 1)
         val lowMask = BooleanArray(sg.size) { it < analysisLimit && sg[it] <= threshold }
         val rawSpans = contiguousTrueSpans(lowMask).filter { it.second - it.first + 1 >= lowMinLen }
 
@@ -409,11 +542,14 @@ class PiezoEchoAnalyzer private constructor() {
         val lowSlice = safeSlice(sg, from = s, to = e) ?: return null
         if (lowSlice.isEmpty()) return null
         val lowMean = lowSlice.sum() / lowSlice.size.toDouble()
-        val peakMin = lowMean + minPeakMargin
+        val peakMin = max(lowMean + minPeakMargin, threshold)
 
         // 3) Prominence 기반 wall peak 선택
-        val ant = selectWallByProminence(sg = sg, edge = s, searchWin = peakSearchWin,
-            peakMin = peakMin, side = WallSide.ANT, otherEdge = e) ?: return null
+        var ant = selectWallByProminence(sg = sg, edge = s, searchWin = peakSearchWin,
+            peakMin = peakMin, side = WallSide.ANT, otherEdge = e)
+        // ant 없으면 span 시작 직전 (단조 감소 대응)
+        if (ant == null && s > 0) ant = s - 1
+        if (ant == null) return null
         var post = selectWallByProminence(sg = sg, edge = e, searchWin = peakSearchWin,
             peakMin = peakMin, side = WallSide.POST, otherEdge = s) ?: return null
 
@@ -433,10 +569,19 @@ class PiezoEchoAnalyzer private constructor() {
         if (postH < threshold) return null
 
         val lowDepth = ((antH + postH) / 2.0) - lowMean
-        val urineLen = post - ant
+        val urineLen = post - ant - 1
 
         if (urineLen < minUrineLen) return null
 
+        // FP 필터: 벽/low 비율
+        val wallMin = min(antH, postH)
+        if (lowMean > 0 && (wallMin / lowMean) < wallLowMeanMinRatio) return null
+
+        val score = lowDepth * urineLen.toDouble()
+
+        // FP 필터: score 최소
+        if (score < minScore) return null
+
         return LowEchoResult(
             ant = ant,
             post = post,
@@ -444,7 +589,7 @@ class PiezoEchoAnalyzer private constructor() {
             lowEnd = e,
             lowMean = lowMean,
             urineLen = urineLen,
-            score = lowDepth * urineLen.toDouble(),
+            score = score,
             innerPeaks = findInnerPeaks(sg, left = ant, right = post)
         )
     }

app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PiezoMonitoringView.kt

@@ -167,12 +167,12 @@ fun PiezoMonitoringView(appState: AppState) {
                         }
                         else -> {
                             methodLabel = "B"
-                            val channelResults = validChannels.map { analyzer.analyzeChannel(it.buffer, it.channel) }
+                            val channelResults = analyzer.analyzeMultiChannelWithTgc(validChannels)
                             for (ch in channelResults) {
                                 if (ch.channel < 6 && ch.result != null) allWalls[ch.channel] = Pair(ch.result.ant, ch.result.post)
                             }
                             for (ch in channelResults) {
-                                if (ch.isValid && ch.result != null) Log.d("PiezoMonitor", "  CH${ch.channel}[B]: ant=${ch.result.ant} post=${ch.result.post} urine=${ch.result.urineLen}")
+                                if (ch.isValid && ch.result != null) Log.d("PiezoMonitor", "  CH${ch.channel}[B]: ant=${ch.result.ant} post=${ch.result.post} urine=${ch.result.urineLen} otsu=${"%.0f".format(analyzer.lastOtsuThreshold)} sep=${"%.2f".format(analyzer.lastOtsuSeparability)}")
                             }
                         }
                     }
@@ -449,15 +449,18 @@ fun PiezoMonitoringView(appState: AppState) {
                             Icon(Icons.Default.ChevronRight, contentDescription = null, tint = MlSecondaryText)
                         }
                     }
-                    // Quick Save (iOS bolt.fill 스타일)
+                    // Quick Save — 현재 측정값으로 저장 + volume 0 리셋
+                    val quickVol = if (lastVolumeMl > 0) lastVolumeMl.toInt() else appState.estimatedVolume
                     Surface(
                         onClick = {
                             com.example.medilightv2android.measure.VoidingRecordStore.add(
                                 context, com.example.medilightv2android.measure.VoidingRecord(
-                                    volume = appState.estimatedVolume, method = "catheterize"
+                                    volume = quickVol, method = "catheterize"
                                 )
                             )
                             appState.resetLevel()
+                            lastVolumeMl = 0.0
+                            maxVolumeMl = 0.0
                             resetMeasurement()
                             android.widget.Toast.makeText(context, context.getString(R.string.registered_diary), android.widget.Toast.LENGTH_SHORT).show()
                             showCatheterizeSheet = false
@@ -472,7 +475,7 @@ fun PiezoMonitoringView(appState: AppState) {
                             Icon(Icons.Default.FlashOn, contentDescription = null, tint = Color(0xFF4CAF50))
                             Spacer(modifier = Modifier.width(12.dp))
                             Text("빠른 저장", fontWeight = FontWeight.SemiBold, modifier = Modifier.weight(1f))
-                            Text("${appState.estimatedVolume} ml", color = MlSecondaryText, fontSize = 14.sp)
+                            Text("$quickVol ml", color = MlSecondaryText, fontSize = 14.sp)
                             Spacer(modifier = Modifier.width(4.dp))
                             Icon(Icons.Default.ChevronRight, contentDescription = null, tint = MlSecondaryText)
                         }
@@ -699,21 +702,23 @@ fun PiezoMonitoringView(appState: AppState) {
             Row(horizontalArrangement = Arrangement.spacedBy(12.dp)) {
                 val displayVol = if (lastVolumeMl > 0) "%.0f".format(lastVolumeMl) else "${appState.estimatedVolume}"
                 InfoCard("Volume", displayVol, "ml", urgency.accentColor, Modifier.weight(1f))
-                InfoCard("Max Vol", if (maxVolumeMl > 0) "%.0f".format(maxVolumeMl) else "—", "ml", Color(0xFFFF9500), Modifier.weight(1f))
                 InfoCard("Fill", String.format("%.0f", appState.fillPercentage), "%", urgency.accentColor, Modifier.weight(1f))
                 InfoCard("Level", "${appState.bladderLevel.currentLevel}/${BladderLevel.MAX_LEVEL}", "", urgency.accentColor, Modifier.weight(1f))
             }
 
-            // Control buttons: Catheterize / Auto / Spot
+            // Control buttons: Void/Catheterize / Auto / Spot
             Row(horizontalArrangement = Arrangement.spacedBy(8.dp)) {
-                // Catheterize
+                // Void / Catheterize
                 Button(
                     onClick = { showCatheterizeSheet = true },
-                    modifier = Modifier.weight(1.2f).height(52.dp),
+                    modifier = Modifier.weight(1.3f).height(56.dp),
                     shape = RoundedCornerShape(14.dp),
                     colors = ButtonDefaults.buttonColors(containerColor = MlPrimary.copy(alpha = 0.1f))
                 ) {
-                    Text("Catheterize", fontSize = 13.sp, fontWeight = FontWeight.SemiBold, color = MlPrimary)
+                    Column(horizontalAlignment = Alignment.CenterHorizontally) {
+                        Text("Void /", fontSize = 11.sp, color = MlPrimary)
+                        Text("Catheterize", fontSize = 13.sp, fontWeight = FontWeight.SemiBold, color = MlPrimary)
+                    }
                 }
 
                 // Auto
@@ -721,7 +726,7 @@ fun PiezoMonitoringView(appState: AppState) {
                     onClick = {
                         if (isAutoMeasuring) stopAutoMeasure() else startAutoMeasure()
                     },
-                    modifier = Modifier.weight(1f).height(52.dp),
+                    modifier = Modifier.weight(1f).height(56.dp),
                     shape = RoundedCornerShape(14.dp),
                     colors = ButtonDefaults.buttonColors(
                         containerColor = if (isAutoMeasuring) Color.Red else Color(0xFFFF9800)
@@ -738,7 +743,7 @@ fun PiezoMonitoringView(appState: AppState) {
                 Button(
                     onClick = { if (!isMeasuring && !isAutoMeasuring) measure() },
                     enabled = !isMeasuring && !isAutoMeasuring,
-                    modifier = Modifier.weight(1f).height(52.dp),
+                    modifier = Modifier.weight(1f).height(56.dp),
                     shape = RoundedCornerShape(14.dp),
                     colors = ButtonDefaults.buttonColors(
                         containerColor = urgency.gradientColors.first()
@@ -1394,7 +1399,7 @@ private fun InfoCard(title: String, value: String, unit: String, color: Color, m
             verticalArrangement = Arrangement.spacedBy(6.dp)
         ) {
             Text(value, fontSize = 20.sp, fontWeight = FontWeight.Bold, color = Color(0xFF1C1B1F))
-            if (unit.isNotEmpty()) Text(unit, fontSize = 11.sp, color = MlSecondaryText)
+            Text(unit.ifEmpty { " " }, fontSize = 11.sp, color = MlSecondaryText)
             Text(title, fontSize = 11.sp, fontWeight = FontWeight.SemiBold, color = MlSecondaryText)
         }
     }

app/src/main/java/com/example/medilightv2android/ui/views/monitoring/PlacementGuideView.kt

@@ -62,7 +62,7 @@ fun PlacementGuideView(appState: AppState) {
     var isContinuousMode by remember { mutableStateOf(false) }
     val channelDetected = remember { mutableStateListOf(false, false, false, false, false, false) }
     val channelUrineLen = remember { mutableStateListOf(0, 0, 0, 0, 0, 0) }
-    var directionHint by remember { mutableStateOf("센서를 아래에서 위로 천천히 이동하세요") }
+    var directionHint by remember { mutableStateOf("치골 위에 센서를 올려놓으세요") }
     var directionIcon by remember { mutableStateOf("") }
     var placementScore by remember { mutableIntStateOf(0) }
     var scanCount by remember { mutableIntStateOf(0) }
@@ -70,6 +70,7 @@ fun PlacementGuideView(appState: AppState) {
     var lastChannelData by remember { mutableStateOf<List<PiezoChannelData>>(emptyList()) }
     var debounceCount by remember { mutableIntStateOf(0) }
     var lastGuidePhase by remember { mutableStateOf(PlacementPhase.VERTICAL) }
+    var lastHintChangeMs by remember { mutableStateOf(0L) }
     var showPlacementSettings by remember { mutableStateOf(false) }
 
     // 2단계 순차 탐색: VERTICAL → LATERAL → GREEN
@@ -81,17 +82,23 @@ fun PlacementGuideView(appState: AppState) {
         isLocked = false
         scanCount = 0
         placementScore = 0
-        directionHint = "센서를 아래에서 위로 천천히 이동하세요"
+        directionHint = "치골 위에 센서를 올려놓으세요"
         directionIcon = ""
         for (i in 0 until 6) { channelDetected[i] = false; channelUrineLen[i] = 0 }
     }
 
     val detectedCount = channelDetected.count { it }
 
+    val isGreenZone = isLocked || placementScore >= 70
+    val bgColor by androidx.compose.animation.animateColorAsState(
+        targetValue = if (isGreenZone) Color(0xFFE8F5E9) else MlBackground,
+        animationSpec = androidx.compose.animation.core.tween(600), label = "bg"
+    )
+
     Column(
         modifier = Modifier
             .fillMaxSize()
-            .background(MlBackground)
+            .background(bgColor)
     ) {
         // Top bar
         Row(
@@ -100,7 +107,7 @@ fun PlacementGuideView(appState: AppState) {
                 .padding(horizontal = 24.dp, vertical = 16.dp),
             verticalAlignment = Alignment.CenterVertically
         ) {
-            IconButton(onClick = { appState.goHome() }) {
+            IconButton(onClick = { appState.currentScreen = if (appState.isDeviceConnected) com.example.medilightv2android.AppScreen.PIEZO_MONITORING else com.example.medilightv2android.AppScreen.HOME }) {
                 Icon(
                     Icons.AutoMirrored.Filled.ArrowBack,
                     contentDescription = "Back",
@@ -131,108 +138,223 @@ fun PlacementGuideView(appState: AppState) {
                 .padding(horizontal = 24.dp),
             horizontalAlignment = Alignment.CenterHorizontally
         ) {
-            // Instructions
-            Text(
-                text = when (placementPhase) {
-                    PlacementPhase.VERTICAL -> "Step 1/3: 센서를 아래에서 위로 천천히 이동하세요"
-                    PlacementPhase.LATERAL -> "Step 2/3: 센서를 좌우로 천천히 이동하세요"
-                    PlacementPhase.GREEN -> "Step 3/3: 최종 위치 확인 중..."
-                },
-                fontSize = 14.sp,
-                color = MlSecondaryText,
-                textAlign = TextAlign.Center,
-                modifier = Modifier.padding(top = 8.dp)
-            )
-
-            Spacer(modifier = Modifier.height(16.dp))
-
-            // Direction guide
-            if (directionHint.isNotEmpty() && !isLocked) {
-                Row(
-                    modifier = Modifier
-                        .fillMaxWidth()
-                        .background(
-                            Color(0xFFFFF3E0),
-                            RoundedCornerShape(14.dp)
-                        )
-                        .padding(16.dp),
-                    verticalAlignment = Alignment.CenterVertically,
-                    horizontalArrangement = Arrangement.spacedBy(12.dp)
-                ) {
-                    val icon = when {
-                        directionIcon.contains("up") -> Icons.Filled.KeyboardArrowUp
-                        directionIcon.contains("down") -> Icons.Filled.KeyboardArrowDown
-                        directionIcon.contains("left") -> Icons.Filled.ArrowBack
-                        directionIcon.contains("right") -> Icons.Filled.ArrowForward
-                        directionIcon.contains("check") -> Icons.Filled.CheckCircle
-                        else -> Icons.Filled.Warning
-                    }
-                    Icon(
-                        icon,
-                        contentDescription = null,
-                        tint = Color(0xFFFF9800),
-                        modifier = Modifier.size(24.dp)
-                    )
-                    Text(
-                        text = directionHint,
-                        fontSize = 16.sp,
-                        fontWeight = FontWeight.SemiBold,
-                        color = Color(0xFFFF9800)
-                    )
-                }
-            }
-
-            Spacer(modifier = Modifier.height(24.dp))
-
-            // Status summary - channel dots row
-            Row(
-                modifier = Modifier.fillMaxWidth(),
-                verticalAlignment = Alignment.CenterVertically,
-                horizontalArrangement = Arrangement.spacedBy(8.dp)
+            // ── 상반신 일러스트 + 센서 + 방향 가이드 ──
+            Box(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .height(300.dp)
+                    .padding(top = 8.dp),
+                contentAlignment = Alignment.Center
             ) {
-                for (i in 0 until 6) {
-                    Column(
-                        horizontalAlignment = Alignment.CenterHorizontally,
-                        verticalArrangement = Arrangement.spacedBy(2.dp)
-                    ) {
-                        Box(
-                            modifier = Modifier
-                                .size(12.dp)
-                                .clip(CircleShape)
-                                .background(
-                                    if (channelDetected[i]) Color(0xFF4CAF50)
-                                    else Color.Red.copy(alpha = 0.4f)
-                                )
-                        )
-                        Text("CH$i", fontSize = 9.sp, fontWeight = FontWeight.SemiBold, color = MlSecondaryText)
-                        if (channelUrineLen[i] > 0) {
-                            Text("${channelUrineLen[i]}", fontSize = 8.sp, color = Color.Cyan)
+                Canvas(modifier = Modifier.fillMaxSize()) {
+                    val w = size.width
+                    val h = size.height
+                    val cx = w / 2f
+                    val greenZone = isGreenZone
+
+                    // ── 상반신 실루엣 ──
+                    val skinColor = Color(0xFFFFDDB5)
+                    val outlineColor = Color(0xFFD4A574)
+
+                    // 몸통 (위: 가슴 아래, 아래: 치골)
+                    val bodyTop = h * 0.05f
+                    val bodyBot = h * 0.88f
+                    val bodyW = w * 0.38f
+
+                    // 몸통 타원형
+                    val bodyPath = Path().apply {
+                        moveTo(cx - bodyW, bodyTop)
+                        // 왼쪽 어깨~허리 곡선
+                        cubicTo(cx - bodyW * 1.15f, bodyTop + h * 0.15f,
+                                cx - bodyW * 0.85f, bodyBot - h * 0.1f,
+                                cx - bodyW * 0.7f, bodyBot)
+                        // 아래쪽 (치골)
+                        lineTo(cx + bodyW * 0.7f, bodyBot)
+                        // 오른쪽 허리~어깨
+                        cubicTo(cx + bodyW * 0.85f, bodyBot - h * 0.1f,
+                                cx + bodyW * 1.15f, bodyTop + h * 0.15f,
+                                cx + bodyW, bodyTop)
+                        close()
+                    }
+                    drawPath(bodyPath, skinColor)
+                    drawPath(bodyPath, outlineColor, style = Stroke(width = 2f))
+
+                    // 배꼽
+                    val navelY = h * 0.40f
+                    drawCircle(outlineColor.copy(alpha = 0.5f), radius = 4f, center = Offset(cx, navelY))
+
+                    // 치골 라인
+                    val pubisY = h * 0.82f
+                    drawLine(outlineColor.copy(alpha = 0.4f),
+                        Offset(cx - bodyW * 0.5f, pubisY),
+                        Offset(cx + bodyW * 0.5f, pubisY),
+                        strokeWidth = 1.5f,
+                        pathEffect = PathEffect.dashPathEffect(floatArrayOf(8f, 4f)))
+
+                    // 방광 (점선 타원, 배꼽과 치골 사이)
+                    val bladderCy = (navelY + pubisY) / 2f
+                    val bladderRx = bodyW * 0.35f
+                    val bladderRy = (pubisY - navelY) * 0.35f
+                    drawOval(
+                        color = if (greenZone) Color(0xFF4CAF50).copy(alpha = 0.15f) else Color.Cyan.copy(alpha = 0.12f),
+                        topLeft = Offset(cx - bladderRx, bladderCy - bladderRy),
+                        size = Size(bladderRx * 2, bladderRy * 2)
+                    )
+                    drawOval(
+                        color = if (greenZone) Color(0xFF4CAF50).copy(alpha = 0.4f) else Color.Cyan.copy(alpha = 0.35f),
+                        topLeft = Offset(cx - bladderRx, bladderCy - bladderRy),
+                        size = Size(bladderRx * 2, bladderRy * 2),
+                        style = Stroke(width = 1.5f, pathEffect = PathEffect.dashPathEffect(floatArrayOf(6f, 4f)))
+                    )
+
+                    // ── 센서 기기 (둥근 사각형) ──
+                    val sensorW = 50f
+                    val sensorH = 70f
+                    val sensorY = bladderCy - sensorH / 2
+                    val sensorColor = if (greenZone) Color(0xFF4CAF50) else MlPrimary
+                    drawRoundRect(
+                        color = sensorColor.copy(alpha = 0.2f),
+                        topLeft = Offset(cx - sensorW / 2, sensorY),
+                        size = Size(sensorW, sensorH),
+                        cornerRadius = CornerRadius(12f)
+                    )
+                    drawRoundRect(
+                        color = sensorColor,
+                        topLeft = Offset(cx - sensorW / 2, sensorY),
+                        size = Size(sensorW, sensorH),
+                        cornerRadius = CornerRadius(12f),
+                        style = Stroke(width = 3f)
+                    )
+
+                    // ── 방향 화살표 ──
+                    if (!greenZone) {
+                        val arrowColor = Color(0xFFFF9800)
+                        val arrowLen = 40f
+                        val arrowHead = 12f
+
+                        when {
+                            directionIcon.contains("up") -> {
+                                val ax = cx; val ay = sensorY - 20f
+                                drawLine(arrowColor, Offset(ax, ay + arrowLen), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax - arrowHead, ay + arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax + arrowHead, ay + arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                            }
+                            directionIcon.contains("down") -> {
+                                val ax = cx; val ay = sensorY + sensorH + 20f
+                                drawLine(arrowColor, Offset(ax, ay - arrowLen), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax - arrowHead, ay - arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax + arrowHead, ay - arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                            }
+                            directionIcon.contains("left") -> {
+                                val ax = cx - sensorW / 2 - 25f; val ay = sensorY + sensorH / 2
+                                drawLine(arrowColor, Offset(ax + arrowLen, ay), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax + arrowHead, ay - arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax + arrowHead, ay + arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                            }
+                            directionIcon.contains("right") -> {
+                                val ax = cx + sensorW / 2 + 25f; val ay = sensorY + sensorH / 2
+                                drawLine(arrowColor, Offset(ax - arrowLen, ay), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax - arrowHead, ay - arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                                drawLine(arrowColor, Offset(ax - arrowHead, ay + arrowHead), Offset(ax, ay), strokeWidth = 4f)
+                            }
                         }
                     }
+
+                    // Green 체크마크
+                    if (greenZone) {
+                        drawCircle(Color(0xFF4CAF50).copy(alpha = 0.2f), radius = 35f, center = Offset(cx, sensorY - 30f))
+                        // ✓ 모양
+                        val checkPath = Path().apply {
+                            moveTo(cx - 15f, sensorY - 30f)
+                            lineTo(cx - 5f, sensorY - 20f)
+                            lineTo(cx + 15f, sensorY - 42f)
+                        }
+                        drawPath(checkPath, Color(0xFF4CAF50), style = Stroke(width = 4f))
+                    }
                 }
-                Spacer(modifier = Modifier.weight(1f))
-                Column(horizontalAlignment = Alignment.End) {
-                    Text(
-                        text = "$detectedCount/6",
-                        fontSize = 16.sp,
-                        fontWeight = FontWeight.Bold,
-                        color = if (detectedCount >= 4) Color(0xFF4CAF50) else Color(0xFFFF9800)
-                    )
+
+                // Score + 감지수 (우측 상단)
+                Column(
+                    modifier = Modifier
+                        .align(Alignment.TopEnd)
+                        .padding(4.dp),
+                    horizontalAlignment = Alignment.End
+                ) {
+                    Text("$detectedCount/6", fontSize = 16.sp, fontWeight = FontWeight.Bold,
+                        color = if (detectedCount >= 4) Color(0xFF4CAF50) else Color(0xFFFF9800))
                     if (placementScore > 0) {
-                        Text(
-                            text = "Score: $placementScore%",
-                            fontSize = 13.sp,
-                            fontWeight = FontWeight.Bold,
+                        Text("$placementScore%", fontSize = 13.sp, fontWeight = FontWeight.Bold,
                             color = when {
                                 placementScore >= 80 -> Color(0xFF4CAF50)
                                 placementScore >= 50 -> Color(0xFFFF9800)
                                 else -> Color.Red
-                            }
-                        )
+                            })
+                    }
+                }
+
+                // 라벨 (좌측)
+                Column(
+                    modifier = Modifier
+                        .align(Alignment.CenterStart)
+                        .padding(start = 4.dp),
+                    verticalArrangement = Arrangement.spacedBy(0.dp)
+                ) {
+                    Text("가슴", fontSize = 9.sp, color = MlSecondaryText)
+                    Spacer(modifier = Modifier.height(60.dp))
+                    Text("배꼽", fontSize = 9.sp, color = MlSecondaryText)
+                    Spacer(modifier = Modifier.height(60.dp))
+                    Text("치골", fontSize = 9.sp, color = MlSecondaryText)
+                }
+            }
+
+            // ── 가이드 텍스트 (일러스트 아래) ──
+            if (directionHint.isNotEmpty()) {
+                val hintGreen = isGreenZone
+                val hintBg = if (hintGreen) Color(0xFF4CAF50).copy(alpha = 0.12f) else Color(0xFFFFF3E0)
+                val hintFg = if (hintGreen) Color(0xFF4CAF50) else Color(0xFFFF9800)
+                Text(
+                    text = directionHint,
+                    fontSize = 15.sp,
+                    fontWeight = FontWeight.SemiBold,
+                    color = hintFg,
+                    textAlign = TextAlign.Center,
+                    modifier = Modifier
+                        .fillMaxWidth()
+                        .background(hintBg, RoundedCornerShape(12.dp))
+                        .padding(12.dp)
+                )
+            }
+
+            Spacer(modifier = Modifier.height(8.dp))
+
+            // 채널 dot row
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.SpaceEvenly,
+                verticalAlignment = Alignment.CenterVertically
+            ) {
+                for (i in 0 until 6) {
+                    Column(horizontalAlignment = Alignment.CenterHorizontally, verticalArrangement = Arrangement.spacedBy(2.dp)) {
+                        Box(modifier = Modifier.size(10.dp).clip(CircleShape).background(
+                            if (channelDetected[i]) Color(0xFF4CAF50) else Color.Red.copy(alpha = 0.35f)
+                        ))
+                        Text("CH$i", fontSize = 8.sp, color = MlSecondaryText)
                     }
                 }
             }
 
+            Spacer(modifier = Modifier.height(4.dp))
+
+            // Step indicator
+            Text(
+                text = when (placementPhase) {
+                    PlacementPhase.VERTICAL -> "Step 1/3"
+                    PlacementPhase.LATERAL -> "Step 2/3"
+                    PlacementPhase.GREEN -> "Step 3/3"
+                },
+                fontSize = 11.sp, color = MlSecondaryText
+            )
+
             // Per-channel echo graphs (after scan)
             if (lastChannelData.isNotEmpty()) {
                 Spacer(modifier = Modifier.height(16.dp))
@@ -380,7 +502,7 @@ fun PlacementGuideView(appState: AppState) {
                     } else {
                         val guideResult = computePlacementGuide(detected, urineLens, allWalls, scanCount, placementPhase)
 
-                        // 디바운스: 같은 phase가 2회 연속일 때만 힌트 변경
+                        // 디바운스: 같은 phase 2회 연속 + 최소 3초 유지
                         if (guideResult.nextPhase == lastGuidePhase) {
                             debounceCount++
                         } else {
@@ -388,11 +510,14 @@ fun PlacementGuideView(appState: AppState) {
                             lastGuidePhase = guideResult.nextPhase
                         }
 
-                        if (debounceCount >= 2 || guideResult.isPass) {
+                        val now = System.currentTimeMillis()
+                        val elapsed = now - lastHintChangeMs
+                        if ((debounceCount >= 2 && elapsed >= 4000) || guideResult.isPass) {
                             directionHint = guideResult.hint
                             directionIcon = guideResult.icon
                             placementScore = guideResult.score
                             placementPhase = guideResult.nextPhase
+                            lastHintChangeMs = now
                         }
 
                         if (guideResult.isPass) {
@@ -777,8 +902,8 @@ data class PlacementGuideResult(
     val nextPhase: PlacementPhase = PlacementPhase.VERTICAL
 )
 
-private const val DEFAULT_CV_THR = 0.15
-private const val DEFAULT_LR_DEV_THR = 0.30
+private const val DEFAULT_CV_THR = 0.10
+private const val DEFAULT_LR_DEV_THR = 0.25
 
 /**
  * 2단계 순차 Placement Guide (대표님 요구사항)
@@ -804,94 +929,113 @@ private fun computePlacementGuide(
     val detectedCount = detected.count { it }
 
     if (detectedCount == 0) {
-        return PlacementGuideResult("No bladder detected. Check sensor contact.", "exclamationmark.triangle", 0,
+        return PlacementGuideResult("방광이 감지되지 않습니다. 센서를 위로 천천히 올려보세요 ↑", "arrow.up", 0,
             phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.VERTICAL)
     }
 
     // Center 채널 정보
     val centerLens = (0..3).map { urineLens.getOrElse(it) { 0 } }
     val centerDetected = (0..3).count { detected.getOrElse(it) { false } }
+    val ch0 = detected.getOrElse(0) { false }
+    val ch1 = detected.getOrElse(1) { false }
+    val ch2 = detected.getOrElse(2) { false }
+    val ch3 = detected.getOrElse(3) { false }
     val len0 = centerLens[0]; val len1 = centerLens[1]
     val len2 = centerLens[2]; val len3 = centerLens[3]
 
-    // ═══ 1단계: 상하 탐색 ═══
+    // ═══ 1단계: 상하 탐색 (치골→위로→CH0 안잡히면 아래로) ═══
     if (currentPhase == PlacementPhase.VERTICAL) {
-        // 조건: 3개 이상 center에서 low echo 검출
         if (centerDetected < 3) {
-            val ch0 = detected.getOrElse(0) { false }
-            val ch3 = detected.getOrElse(3) { false }
-            val hint = when {
-                ch3 && !ch0 -> "센서를 아래로 이동하세요 ↓"
-                !ch3 && ch0 -> "센서를 위로 이동하세요 ↑"
-                else -> "센서를 천천히 위아래로 이동하세요"
-            }
-            val icon = when {
-                ch3 && !ch0 -> "arrow.down"
-                !ch3 && ch0 -> "arrow.up"
-                else -> "arrow.up.arrow.down"
+            val hint: String
+            val icon: String
+            when {
+                // 위쪽만 잡힘 → 아래로 내리세요
+                (ch3 || ch2) && !ch0 && !ch1 -> {
+                    hint = "센서를 아래로 천천히 내리세요 ↓"
+                    icon = "arrow.down"
+                }
+                // 아래쪽만 잡힘 → 위로 올리세요
+                (ch0 || ch1) && !ch3 && !ch2 -> {
+                    hint = "센서를 위로 천천히 올리세요 ↑"
+                    icon = "arrow.up"
+                }
+                // 아무것도 또는 1개만 → 위로 올리세요 (치골에서 시작 기준)
+                else -> {
+                    hint = "센서를 위로 천천히 올리세요 ↑"
+                    icon = "arrow.up"
+                }
             }
             return PlacementGuideResult(hint, icon, centerDetected * 10,
                 phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.VERTICAL)
         }
 
-        // 3개 이상 검출 — 크기 패턴 확인 (3≥2≥1≥0 또는 유사)
+        // 3개 이상 검출 — CH0 유무 확인
+        if (!ch0 && ch3) {
+            return PlacementGuideResult("CH0이 약합니다. 센서를 아래로 조금 내리세요 ↓", "arrow.down", 25,
+                phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.VERTICAL)
+        }
+
+        // 크기 패턴 확인
         val validLens = (0..3).filter { detected.getOrElse(it) { false } }.map { centerLens[it] }
         val maxLen = validLens.maxOrNull() ?: 0
         val minLen = validLens.minOrNull() ?: 0
         val lenVariation = if (maxLen > 0) (maxLen - minLen).toDouble() / maxLen else 1.0
 
-        // 크기가 유사(변동 < 50%) 또는 3≥2≥1≥0 패턴
-        val isOrdered = len3 >= len2 - 5 && len2 >= len1 - 5 && (len0 == 0 || len1 >= len0 - 5)
-        val isSimilar = lenVariation < 0.5
-
-        if (isSimilar || isOrdered) {
-            // 상하 PASS → 2단계 좌우로
+        if (lenVariation < 0.5) {
+            val l4 = urineLens.getOrElse(4) { 0 }
+            val l5 = urineLens.getOrElse(5) { 0 }
+            val lrHint = when {
+                l4 > 0 && l5 > 0 && l4 > l5 -> "오른쪽으로 이동하세요 →"
+                l4 > 0 && l5 > 0 && l5 > l4 -> "왼쪽으로 이동하세요 ←"
+                else -> "좌우로 천천히 이동하세요 ↔"
+            }
+            val lrIcon = when {
+                l4 > 0 && l5 > 0 && l4 > l5 -> "arrow.right"
+                l4 > 0 && l5 > 0 && l5 > l4 -> "arrow.left"
+                else -> "arrow.left.arrow.right"
+            }
             return PlacementGuideResult(
-                "상하 위치 OK! 좌우로 천천히 이동하세요 ↔",
-                "arrow.left.arrow.right", 40,
+                "상하 위치 OK! $lrHint",
+                lrIcon, 40,
                 phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.LATERAL)
         } else {
-            // 크기 편차 큼 → 상하 더 조절
             return if (len3 > len0 * 2) {
-                PlacementGuideResult("센서를 아래로 더 이동하세요 ↓ (CH0 약함)", "arrow.down", 25,
+                PlacementGuideResult("센서를 아래로 조금 내리세요 ↓", "arrow.down", 25,
                     phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.VERTICAL)
             } else {
-                PlacementGuideResult("센서를 위로 더 이동하세요 ↑ (CH3 약함)", "arrow.up", 25,
+                PlacementGuideResult("센서를 위로 조금 올리세요 ↑", "arrow.up", 25,
                     phase = PlacementPhase.VERTICAL, nextPhase = PlacementPhase.VERTICAL)
             }
         }
     }
 
-    // ═══ 2단계: 좌우 탐색 ═══
+    // ═══ 2단계: 좌우 대칭 맞추기 ═══
     if (currentPhase == PlacementPhase.LATERAL) {
         val len4 = urineLens.getOrElse(4) { 0 }
         val len5 = urineLens.getOrElse(5) { 0 }
         val ch4 = detected.getOrElse(4) { false }
         val ch5 = detected.getOrElse(5) { false }
 
-        // 먼저 상하가 여전히 유효한지 확인
         if (centerDetected < 3) {
-            return PlacementGuideResult("상하 위치 벗어남 — 다시 위아래 조절", "arrow.up.arrow.down", 20,
+            return PlacementGuideResult("상하 위치 벗어남 — 위아래 다시 조절", "arrow.up.arrow.down", 20,
                 phase = PlacementPhase.LATERAL, nextPhase = PlacementPhase.VERTICAL)
         }
 
         if (!ch4 && !ch5) {
-            return PlacementGuideResult("좌우로 천천히 이동하세요 ↔", "arrow.left.arrow.right", 40,
+            return PlacementGuideResult("좌우 센서가 감지되지 않습니다. 좌우로 이동하세요 ↔", "arrow.left.arrow.right", 40,
                 phase = PlacementPhase.LATERAL, nextPhase = PlacementPhase.LATERAL)
         }
 
-        // 좌우 대칭성 판정
         val lrMax = maxOf(len4, len5, 1)
         val lrSymmetry = 1.0 - kotlin.math.abs(len4 - len5).toDouble() / lrMax
 
         if (lrSymmetry >= 0.7 || (ch4 && ch5)) {
-            // 좌우 PASS → 3단계 CV 확인
             return PlacementGuideResult(
                 "좌우 대칭 OK! 최종 확인 중...",
                 "checkmark.circle", 60,
                 phase = PlacementPhase.LATERAL, nextPhase = PlacementPhase.GREEN)
         } else {
-            val hint = if (len4 > len5) "센서를 오른쪽으로 이동 → (CH4 더 김)" else "센서를 왼쪽으로 이동 ← (CH5 더 김)"
+            val hint = if (len4 > len5) "센서를 오른쪽으로 이동 →" else "센서를 왼쪽으로 이동 ←"
             val icon = if (len4 > len5) "arrow.right" else "arrow.left"
             return PlacementGuideResult(hint, icon, 45,
                 phase = PlacementPhase.LATERAL, nextPhase = PlacementPhase.LATERAL)
@@ -926,7 +1070,7 @@ private fun computePlacementGuide(
     val std = kotlin.math.sqrt(depths.map { (it - mean) * (it - mean) }.average())
     val cv = if (mean > 0) std / mean else Double.MAX_VALUE
 
-    val relaxStep = (repeatCount / 5).coerceAtMost(3)
+    val relaxStep = (repeatCount / 8).coerceAtMost(2)
     val cvThr = DEFAULT_CV_THR + relaxStep * 0.05
 
     // LR deviation