Merge branch 'master' into jingwen

app/src/main/java/com/example/jnicpp/bowling/BowlingCameraActivity.kt

@@ -307,10 +307,17 @@ class BowlingCameraActivity : AppCompatActivity(), CameraXController.Callback {
                 // Combined with poseEnabled (rather than posePhase alone) so
                 // the label can tell "pose off" (hidden) apart from "pose on
                 // but not yet in the target posture" (amber prompt) -- both
-                // cases otherwise report a null phase.
+                // cases otherwise report a null phase. poseCorrection rides
+                // along the same collector (rather than its own, like
+                // poseMetrics below) since it directly changes what
+                // renderPosePhase puts in the label -- see that function.
                 launch {
-                    combine(viewModel.poseEnabled, viewModel.posePhase) { enabled, phase -> enabled to phase }
-                        .collect { (enabled, phase) -> renderPosePhase(enabled, phase) }
+                    combine(
+                        viewModel.poseEnabled,
+                        viewModel.posePhase,
+                        viewModel.poseCorrection,
+                    ) { enabled, phase, correction -> Triple(enabled, phase, correction) }
+                        .collect { (enabled, phase, correction) -> renderPosePhase(enabled, phase, correction) }
                 }
                 // Raw angle readout backing the label above -- its own
                 // collector since it's driven by a separate StateFlow
@@ -395,15 +402,24 @@ class BowlingCameraActivity : AppCompatActivity(), CameraXController.Callback {
      *
      * @param poseEnabled Whether pose detection is currently on at all.
      * @param phase The bowler's current delivery phase, or null if none currently validates.
+     * @param correction A specific "here's what to fix" instruction from
+     *        [PosePhaseDetector] when [phase] is null and the bowler is
+     *        being measured against one of the stationary phases (starting
+     *        stance, pushaway, slide & release) -- shown in place of the
+     *        generic "waiting" message when present, so the bowler knows
+     *        exactly what to adjust instead of just that they're not there yet.
      */
-    private fun renderPosePhase(poseEnabled: Boolean, phase: BowlingPhase?) {
+    private fun renderPosePhase(poseEnabled: Boolean, phase: BowlingPhase?, correction: String?) {
         if (!poseEnabled) {
             binding.textPoseFeedback.visibility = View.GONE
             return
         }
         binding.textPoseFeedback.visibility = View.VISIBLE
-        // Every other BowlingPhase falls back to the "waiting" message too --
-        // see PosePhaseDetector's class doc, only STARTING_STANCE is detected today.
+        // Every confirmed phase gets its own label/color below; an
+        // unconfirmed one falls back to a specific correction when
+        // PosePhaseDetector has one (see its class doc), otherwise the
+        // generic "waiting" message -- e.g. mid-approach, where per-frame
+        // correction isn't meaningful.
         when (phase) {
             BowlingPhase.STARTING_STANCE -> {
                 binding.textPoseFeedback.text = getString(R.string.pose_phase_starting_stance)
@@ -434,7 +450,7 @@ class BowlingCameraActivity : AppCompatActivity(), CameraXController.Callback {
                 binding.textPoseFeedback.setBackgroundColor(ContextCompat.getColor(this, R.color.Follow_through_ready))
             }
             else -> {
-                binding.textPoseFeedback.text = getString(R.string.pose_phase_waiting)
+                binding.textPoseFeedback.text = correction ?: getString(R.string.pose_phase_waiting)
                 binding.textPoseFeedback.setBackgroundColor(ContextCompat.getColor(this, R.color.Starting_stance_waiting))
             }
         }

app/src/main/java/com/example/jnicpp/bowling/CameraViewModel.kt

@@ -88,6 +88,13 @@ class CameraViewModel(application: Application) : AndroidViewModel(application)
     //This frame's torso/knee/elbow angle readings, or null if pose detection is off.
     val poseMetrics: StateFlow<PosePhaseDetector.Metrics?> = _poseMetrics.asStateFlow()
 
+    // Specific "here's what to fix" instruction while holding one of the
+    // stationary phases (starting stance, pushaway, slide & release) -- see
+    // PosePhaseDetector.correctionFor's doc for why only those three.
+    private val _poseCorrection = MutableStateFlow<String?>(null)
+    /** @brief Live corrective instruction for the current stationary phase, or null if nothing to correct. */
+    val poseCorrection: StateFlow<String?> = _poseCorrection.asStateFlow()
+
     /** @brief Steps detected so far in the current attempt, since the last reset. */
     val stepEvents: StateFlow<List<StepEvent>> get() = stepCountingSession.stepEvents
 
@@ -132,6 +139,7 @@ class CameraViewModel(application: Application) : AndroidViewModel(application)
             posePhaseDetector.reset()
             _posePhase.value = null
             _poseMetrics.value = null
+            _poseCorrection.value = null
         }
     }
 
@@ -153,6 +161,7 @@ class CameraViewModel(application: Application) : AndroidViewModel(application)
         val phaseResult = posePhaseDetector.update(landmarks, angles)
         _posePhase.value = phaseResult.phase
         _poseMetrics.value = phaseResult.metrics
+        _poseCorrection.value = phaseResult.correction
 
         // Check if the current pose matches the Starting Stance (pure posture query)
         val isStartingStance = (phaseResult.phase == BowlingPhase.STARTING_STANCE)

app/src/main/java/com/example/jnicpp/bowling/PosePhaseDetector.kt

@@ -22,8 +22,7 @@ enum class BowlingPhase {
     PUSHAWAY,
     BACK_SWING,
     POWER_STEP,
-    SLIDE_AND_RELEASE,
-    FOLLOW_THROUGH
+    SLIDE_AND_RELEASE
 }
 
 /**
@@ -39,22 +38,57 @@ enum class BowlingPhase {
  *
  * [update] is fed one frame's landmarks/angles at a time, in recording (or
  * live-preview) order. A posture only "counts" once a decaying progress
- * counter (see [validFrameProgress]) climbs to [REQUIRED_CONSECUTIVE_FRAMES]
+ * counter (see [validFrameProgress]) climbs to [requiredConsecutiveFrames]
  * -- this filters out a momentary, correct-looking pose caught mid-transition
  * (e.g. a fleeting instant during the approach where the knee angle briefly
  * passes through the starting-stance range) while still tolerating the
  * occasional single-frame jitter a held stance sees in practice (see
  * [update]'s doc for why this decays rather than resets outright). Once
  * confirmed, it keeps reporting that phase through any invalid streak
- * shorter than [REQUIRED_INVALID_FRAMES_TO_EXIT], reverting to null only once
+ * shorter than [requiredInvalidFramesToExit], reverting to null only once
  * that streak runs longer.
+ *
+ * @param torsoTiltMinDegrees Minimum forward torso lean from vertical
+ *        (shoulder-midpoint-to-hip-midpoint vector vs. vertical) still
+ *        considered a starting-stance lean, in degrees.
+ * @param torsoTiltMaxDegrees Maximum forward torso lean from vertical still
+ *        considered a starting-stance lean, in degrees.
+ * @param kneeAngleMinDegrees Minimum hip-knee-ankle angle still considered
+ *        a near-straight standing leg, in degrees.
+ * @param kneeAngleMaxDegrees Maximum hip-knee-ankle angle still considered
+ *        a near-straight standing leg, in degrees.
+ * @param elbowAngleMinDegrees Minimum shoulder-elbow-wrist angle still
+ *        considered "holding the ball in front", in degrees.
+ * @param elbowAngleMaxDegrees Maximum shoulder-elbow-wrist angle still
+ *        considered "holding the ball in front", in degrees.
+ * @param requiredConsecutiveFrames Target value for [validFrameProgress]
+ *        (which increments by 1 on a valid frame, decrements by 1 -- not
+ *        reset to 0 -- on an invalid one) before [update] starts reporting
+ *        [BowlingPhase.STARTING_STANCE]. Despite the name, this is no
+ *        longer a strict run of consecutive valid frames; see [update]'s doc.
+ * @param requiredInvalidFramesToExit How many consecutive frames the
+ *        posture must fail to validate before [update] stops reporting
+ *        [BowlingPhase.STARTING_STANCE] once it's already been confirmed.
+ *        Deliberately separate from [requiredConsecutiveFrames] -- angle
+ *        readings jitter a couple of degrees frame-to-frame even when the
+ *        bowler is genuinely holding still, so reverting to null on the very
+ *        first out-of-range frame (as opposed to requiring several in a
+ *        row, same as confirming the stance in the first place) makes the
+ *        label flicker between "confirmed" and "waiting" on that jitter
+ *        alone rather than on an actual change of posture.
  */
-class PosePhaseDetector {
-    // Timing constants for stability -- see update() for how they are used.
-    companion object {
-        private const val REQUIRED_CONSECUTIVE_FRAMES = 8
-        private const val REQUIRED_INVALID_FRAMES_TO_EXIT = 5
-    }
+class PosePhaseDetector(
+    private val torsoTiltMinDegrees: Float = 1f,
+    private val torsoTiltMaxDegrees: Float = 15f,
+    private val kneeAngleMinDegrees: Float = 150f,
+    private val kneeAngleMaxDegrees: Float = 180f,
+    private val elbowAngleMinDegrees: Float = 70f,
+    private val elbowAngleMaxDegrees: Float = 125f,
+    private val requiredConsecutiveFrames: Int = 8,
+    private val requiredInvalidFramesToExit: Int = 5,
+) {
+    // Shared parameters for all phases (consecutive frames, etc) could be
+    // split out, but for now they're reused from the constructor.
 
     // Decaying progress toward confirming a phase -- see update()'s
     // doc for why this decays by one on an invalid frame rather than
@@ -64,9 +98,13 @@ class PosePhaseDetector {
     private var currentPhase: BowlingPhase? = null
 
     /**
-     * The actual angles we calculate from the camera for one frame, so can show stuff like "Torso 12°".
+     * @brief The raw angle readings [update] computed for one frame, for
+     *        callers that want to show the bowler the actual numbers (e.g.
+     *        "Torso 12°") rather than just a pass/fail phase.
      *
-     * Each field is null if the camera isn't sure where that body part is.
+     * Each field is null exactly when the landmarks it depends on weren't
+     * confidently detected that frame (see [reliable]) -- same meaning as a
+     * null field elsewhere in this codebase (e.g. [PoseAngles]).
      *
      * @param torsoTiltDegrees See [torsoTiltDegrees].
      * @param leftKneeAngleDegrees Left hip-knee-ankle angle, or null.
@@ -79,22 +117,35 @@ class PosePhaseDetector {
         val leftKneeAngleDegrees: Float?,
         val rightKneeAngleDegrees: Float?,
         val leftElbowAngleDegrees: Float?,
-        val rightElbowAngleDegrees: Float?
+        val rightElbowAngleDegrees: Float?,
     )
 
     /**
-     * get back after checking a frame: the phase and the angles.
+     * @brief One [update] call's outcome: the classified phase plus the raw angles it was based on.
      * @param phase See [update]'s return doc.
      * @param metrics This frame's raw angle readings, for display regardless of whether [phase] validated.
+     * @param correction A specific corrective instruction (e.g. "Straighten
+     *        your legs") when the bowler is being measured against one of
+     *        [STATIONARY_PHASES] but doesn't currently match it, or null
+     *        when there's nothing to correct -- either because the current
+     *        posture already validates, the target phase is one of the
+     *        moving phases this detector doesn't give live corrections for
+     *        (see [correctionFor]'s doc), or a needed angle wasn't
+     *        confidently read this frame.
      */
-    data class Result(val phase: BowlingPhase?, val metrics: Metrics)
+    data class Result(val phase: BowlingPhase?, val metrics: Metrics, val correction: String? = null)
 
     /**
-     * Check one frame from the camera to see what the bowler is doing.
+     * @brief Feeds one frame's landmarks/angles into the detector.
      *
-     * @param landmarks The x,y points of all body parts (already smoothed).
-     * @param angles The joint angles we already calculated for this frame.
-     * @return The updated phase and the raw metrics for this frame.
+     * @param landmarks Smoothed landmarks for this frame, keyed by ML Kit's `PoseLandmark` type constant.
+     * @param angles Joint angles computed for this same frame (see
+     *        [PoseAngleCalculator]) -- elbow angles are reused from here
+     *        rather than recomputed, so this detector doesn't duplicate that math.
+     * @return This frame's [Metrics] alongside [BowlingPhase.STARTING_STANCE]
+     *         once [validFrameProgress] has climbed to [requiredConsecutiveFrames],
+     *         continuing to report it through brief invalid streaks shorter
+     *         than [requiredInvalidFramesToExit], otherwise alongside a null phase.
      */
     fun update(landmarks: Map<Int, SmoothedLandmark>, angles: PoseAngles): Result {
         val metrics = Metrics(
@@ -105,53 +156,39 @@ class PosePhaseDetector {
             rightElbowAngleDegrees = angles.rightElbow
         )
 
-        // Identify the next phase we are looking for in the sequence.
-        val targetPhase = when (currentPhase) {
+        // If the posture matches starting stance, target starting stance even if currently in another phase
+        val isStartingValid = isStartingStanceValid(metrics)
+        val targetPhase = if ((isStartingValid && currentPhase != BowlingPhase.STARTING_STANCE)) {
+            BowlingPhase.STARTING_STANCE
+        } else {
+            when (currentPhase) {
                 null -> BowlingPhase.STARTING_STANCE
                 BowlingPhase.STARTING_STANCE -> BowlingPhase.APPROACH
                 BowlingPhase.APPROACH -> BowlingPhase.PUSHAWAY
-            BowlingPhase.PUSHAWAY -> BowlingPhase.SLIDE_AND_RELEASE
-            BowlingPhase.SLIDE_AND_RELEASE -> BowlingPhase.FOLLOW_THROUGH
-            else -> currentPhase
+                BowlingPhase.PUSHAWAY -> BowlingPhase.BACK_SWING
+                BowlingPhase.BACK_SWING -> BowlingPhase.POWER_STEP
+                BowlingPhase.POWER_STEP -> BowlingPhase.SLIDE_AND_RELEASE
+                // The only BowlingPhase not already matched above -- every
+                // other case (including null) is explicit, so reaching here
+                // means currentPhase is SLIDE_AND_RELEASE, there's no phase
+                // after it to advance to.
+                else -> BowlingPhase.SLIDE_AND_RELEASE
+            }
         }
 
         // 1. Check if the user is in the NEXT phase.
-        var isTargetValid = when (targetPhase) {
-            BowlingPhase.STARTING_STANCE -> isStartingStanceValid(metrics)
+        val isTargetValid = when (targetPhase) {
+            BowlingPhase.STARTING_STANCE -> isStartingValid
             BowlingPhase.APPROACH -> isApproachValid(metrics)
             BowlingPhase.PUSHAWAY -> isPushawayValid(metrics)
-            BowlingPhase.SLIDE_AND_RELEASE -> isSlideReleaseValid(metrics, landmarks)
-            BowlingPhase.FOLLOW_THROUGH -> isFollowThroughValid(metrics, landmarks)
-            else -> false
-        }
-
-        //  SKIP-AHEAD: Check if the user jumped to a LATER phase in the sequence.
-        val allPhases = BowlingPhase.entries
-        val currentIdx = currentPhase?.ordinal ?: -1
-
-        // Look through all future phases.
-        for (i in (currentIdx + 2) until allPhases.size) {
-            val p = allPhases[i]
-
-            val isThisValid = when (p) {
-                BowlingPhase.APPROACH -> isApproachValid(metrics)
-                BowlingPhase.PUSHAWAY -> isPushawayValid(metrics)
-                BowlingPhase.SLIDE_AND_RELEASE -> isSlideReleaseValid(metrics, landmarks)
-                BowlingPhase.FOLLOW_THROUGH -> isFollowThroughValid(metrics, landmarks)
-                else -> false
-            }
-            if (isThisValid) {
-                currentPhase = p
-                validFrameProgress = REQUIRED_CONSECUTIVE_FRAMES
-                consecutiveInvalidFrames = 0
-                isTargetValid = true
-                break
-            }
+            BowlingPhase.BACK_SWING -> isBackSwingValid(metrics)
+            BowlingPhase.POWER_STEP -> isPowerStepValid(metrics)
+            BowlingPhase.SLIDE_AND_RELEASE -> isSlideAndReleaseValid(metrics)
         }
 
         if (isTargetValid) {
-            validFrameProgress = (validFrameProgress + 1).coerceAtMost(REQUIRED_CONSECUTIVE_FRAMES)
-            if (validFrameProgress >= REQUIRED_CONSECUTIVE_FRAMES) {
+            validFrameProgress = (validFrameProgress + 1).coerceAtMost(requiredConsecutiveFrames)
+            if (validFrameProgress >= requiredConsecutiveFrames) {
                 currentPhase = targetPhase
                 validFrameProgress = 0
                 consecutiveInvalidFrames = 0
@@ -161,16 +198,14 @@ class PosePhaseDetector {
         }
 
         // 2. Check if the user has broken their CURRENT confirmed phase.
-        // If they are neither in the target phase nor the current phase, count an invalid frame.
         val isCurrentStillValid = when (currentPhase) {
             BowlingPhase.STARTING_STANCE -> isStartingStanceValid(metrics)
             BowlingPhase.APPROACH -> isApproachValid(metrics)
             BowlingPhase.PUSHAWAY -> isPushawayValid(metrics)
-            BowlingPhase.BACK_SWING -> false
-            BowlingPhase.POWER_STEP -> false
-            BowlingPhase.SLIDE_AND_RELEASE -> isSlideReleaseValid(metrics, landmarks)
-            BowlingPhase.FOLLOW_THROUGH -> isFollowThroughValid(metrics, landmarks)
-            else -> true // If null, only care about progress toward STARTING_STANCE
+            BowlingPhase.BACK_SWING -> isBackSwingValid(metrics)
+            BowlingPhase.POWER_STEP -> isPowerStepValid(metrics)
+            BowlingPhase.SLIDE_AND_RELEASE -> isSlideAndReleaseValid(metrics)
+            else -> true
         }
 
         if (isCurrentStillValid || isTargetValid) {
@@ -180,13 +215,19 @@ class PosePhaseDetector {
         }
 
         // 3. Handle resets: If we lose the current posture for too long, reset to null.
-        if (consecutiveInvalidFrames >= REQUIRED_INVALID_FRAMES_TO_EXIT) {
+        if (consecutiveInvalidFrames >= requiredInvalidFramesToExit) {
             currentPhase = null
             validFrameProgress = 0
             consecutiveInvalidFrames = 0
         }
 
-        return Result(currentPhase, metrics)
+        val correction = if (!isTargetValid && targetPhase in STATIONARY_PHASES) {
+            correctionFor(targetPhase, metrics)
+        } else {
+            null
+        }
+
+        return Result(currentPhase, metrics, correction)
     }
 
     /** @brief Clears all detection state. Call at the start of a new session/attempt. */
@@ -206,22 +247,17 @@ class PosePhaseDetector {
      * actually see.
      *
      * @param metrics This frame's raw angle readings.
-     * @return true if torso lean, knees, and elbows are all in the right spot.
+     * @return true if torso tilt, both visible knee angles, and both visible elbow angles all fall within range.
      */
     fun isStartingStanceValid(metrics: Metrics): Boolean {
-        // Check if the body is mostly upright (tilt between 1 and 20 degrees).
         val torsoTilt = metrics.torsoTiltDegrees ?: return false
-        if (torsoTilt !in 1f..20f) return false
+        if (torsoTilt !in torsoTiltMinDegrees..torsoTiltMaxDegrees) return false
 
-        // Check if both knees are fairly straight (angle above 150 degrees).
         val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
-        if (kneeAngles.isEmpty() || kneeAngles.any { it !in 150f..180f }) return false
+        if (kneeAngles.isEmpty() || kneeAngles.any { it !in kneeAngleMinDegrees..kneeAngleMaxDegrees }) return false
 
-        // Check if elbows are folded (angle between 70 and 125 degrees) while holding the ball.
         val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
-        if (elbowAngles.isEmpty() || elbowAngles.any { it !in 70f..125f }) return false
-
-        return true
+        return elbowAngles.isNotEmpty() && elbowAngles.all { it in elbowAngleMinDegrees..elbowAngleMaxDegrees }
     }
 
     /**
@@ -235,133 +271,192 @@ class PosePhaseDetector {
      * @param metrics This frame's raw angle readings.
      * @return true if torso tilt, knee angles, and elbow angles fall within range.
      */
-    fun isApproachValid(metrics: Metrics): Boolean {
-        // Check if they have a slight forward lean (5 to 30 degrees).
+    private fun isApproachValid(metrics: Metrics): Boolean {
         val torsoTilt = metrics.torsoTiltDegrees ?: return false
-        if (torsoTilt !in 5f..30f) return false
+        if (torsoTilt !in 5f..20f) return false
 
-        // Check if legs are still mostly straight during the walk.
         val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
         if (kneeAngles.isEmpty() || kneeAngles.any { it !in 145f..180f }) return false
 
-        // Check if arm is still close to the body (angle between 60 and 140 degrees).
         val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
-        if (elbowAngles.isEmpty() || elbowAngles.any { it !in 60f..140f }) return false
-
-        return true
+        return elbowAngles.isNotEmpty() && elbowAngles.all { it in 60f..130f }
     }
 
     /**
      * @brief Checks whether this single frame's [Metrics] match the pushaway phase.
      *
      * Pushaway is characterized by:
-     * - Torso Tilt: 5-25 degrees (leaning more)
+     * - Torso Tilt: 5-25 degrees (more lean than stance)
      * - Knee Angle: 145-180 degrees (legs still mostly straight)
      * - Elbow Angle: 130-180 degrees (bowling arm extending forward)
      *
      * @param metrics This frame's raw angle readings.
      * @return true if torso tilt, knee angles, and at least one elbow angle fall within range.
      */
-    fun isPushawayValid(metrics: Metrics): Boolean {
-        // Check if torso lean is between 5 and 25 degrees.
+    private fun isPushawayValid(metrics: Metrics): Boolean {
         val torsoTilt = metrics.torsoTiltDegrees ?: return false
         if (torsoTilt !in 5f..25f) return false
 
         val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
         if (kneeAngles.isEmpty() || kneeAngles.any { it !in 145f..180f }) return false
 
-        // Check if at least one arm is extending forward (angle between 130 and 180 degrees).
+        // For Pushaway, the bowling arm extends. We look for *at least one*
+        // elbow to be extended (130-180), since we don't know the bowler's handedness.
         val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
-        if (elbowAngles.isEmpty() || elbowAngles.none { it in 130f..180f }) return false
-
-        return true
+        return elbowAngles.isNotEmpty() && elbowAngles.any { it in 130f..180f }
     }
 
+    /** @brief Placeholder validation for Backswing phase (Step 3). */
+    @Suppress("UNUSED_PARAMETER")
+    private fun isBackSwingValid(metrics: Metrics): Boolean = true
+
+    /** @brief Placeholder validation for Power Step phase (Step 4). */
+    @Suppress("UNUSED_PARAMETER")
+    private fun isPowerStepValid(metrics: Metrics): Boolean = true
+
     /**
-     * @brief Checks whether this single frame's [Metrics] match the slide and release phase.
+     * @brief Checks whether this single frame's [Metrics] match the slide &
+     *        release phase (finishing position, step 5).
      *
-     * Slide & Release is characterized by:
-     * - Torso Tilt: 15-45 degrees
-     * - Knee Angle: 90-150 degrees (sliding knee)
-     * - Elbow Angle: 150-180 degrees
-     * - Hand Position: Below shoulder (so we know it's not the backswing)
+     * Slide & release is characterized by:
+     * - Torso Tilt: 15-45 degrees (the deepest forward lean of any phase --
+     *   the bowler is bent into the slide)
+     * - Knee Angle: at least one knee bent to 90-150 degrees (the
+     *   sliding/front leg lowers the body through the release; requiring
+     *   only one, not both, since we don't know which leg is forward)
+     * - Elbow Angle: at least one elbow extended to 150-180 degrees (the
+     *   swing arm straightens through the release -- same release cue
+     *   [PoseStageAdvisor] already uses for its own final-step check)
      *
      * @param metrics This frame's raw angle readings.
-     * @param landmarks Current frame's raw landmarks.
-     * @return true if they are actually releasing the ball.
+     * @return true if torso tilt, at least one bent knee, and at least one extended elbow all fall within range.
      */
-    fun isSlideReleaseValid(metrics: Metrics, landmarks: Map<Int, SmoothedLandmark>): Boolean {
-        // Check for a deeper forward lean (15 to 45 degrees).
+    private fun isSlideAndReleaseValid(metrics: Metrics): Boolean {
         val torsoTilt = metrics.torsoTiltDegrees ?: return false
         if (torsoTilt !in 15f..45f) return false
 
-        // Sliding knee deepest bend: 90-150.
         val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
         if (kneeAngles.isEmpty() || kneeAngles.none { it in 90f..150f }) return false
 
-        // Arm near straight: 150-180.
         val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
-        if (elbowAngles.isEmpty() || elbowAngles.none { it in 150f..180f }) return false
-
-        // Check if at least one wrist is below the shoulder (avoids backswing mis-detection)
-        val shoulderY = midpoint(landmarks, PoseLandmark.LEFT_SHOULDER, PoseLandmark.RIGHT_SHOULDER)?.second ?: return false
-        val leftWristY = reliable(landmarks, PoseLandmark.LEFT_WRIST)?.y
-        val rightWristY = reliable(landmarks, PoseLandmark.RIGHT_WRIST)?.y
-        val anyWristBelowShoulder = (leftWristY != null && leftWristY > shoulderY) || (rightWristY != null && rightWristY > shoulderY)
-        if (!anyWristBelowShoulder) return false
-
-        return true
+        return elbowAngles.isNotEmpty() && elbowAngles.any { it in 150f..180f }
     }
 
     /**
-     * @brief Checks whether this single frame's [Metrics] match the follow through phase.
+     * @brief Produces a specific corrective instruction for why [metrics]
+     *        doesn't currently match [targetPhase].
      *
-     * Follow Through is characterized by:
-     * - Torso Tilt: 10-40 degrees
-     * - Knee Angle: 100-165 degrees (sliding knee)
-     * - Elbow Angle: 140-180 degrees
-     * - Hand Position: Above shoulder AND in front of the body
+     * Only covers [STATIONARY_PHASES] -- the three phases a bowler actually
+     * holds still in long enough for frame-by-frame angle feedback to be
+     * meaningful. The remaining phases (approach, backswing, power step) are
+     * mid-motion by nature, so a per-frame "here's what's wrong" cue would
+     * either be stale by the time it's read or just describe normal
+     * transitional movement as an error; those are left to [update]'s
+     * existing pass/fail phase label instead.
      *
-     * @param metrics The angles for this frame.
-     * @param landmarks The points of the body (to check hand position).
-     * @return True if arm is extended high in front of the body.
+     * Checks each phase's conditions in the same order as its `isXValid`
+     * counterpart and returns on the first one that fails, so the bowler
+     * gets one actionable instruction at a time rather than a list.
+     *
+     * @param targetPhase Which stationary phase to check [metrics] against. Must be one of [STATIONARY_PHASES].
+     * @param metrics This frame's raw angle readings.
+     * @return A short corrective instruction, or null if [metrics] already
+     *         validates for [targetPhase] (nothing to correct) or a needed
+     *         angle wasn't confidently read this frame (nothing useful to say yet).
      */
-    fun isFollowThroughValid(metrics: Metrics, landmarks: Map<Int, SmoothedLandmark>): Boolean {
-        val torsoTilt = metrics.torsoTiltDegrees ?: return false
-        if (torsoTilt !in 10f..40f) return false
-
-        // Sliding knee: 100-165.
+    private fun correctionFor(targetPhase: BowlingPhase, metrics: Metrics): String? = when (targetPhase) {
+        BowlingPhase.STARTING_STANCE -> {
+            val torsoTilt = metrics.torsoTiltDegrees
             val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
-        if (kneeAngles.isEmpty() || kneeAngles.none { it in 100f..165f }) return false
-
-        // Arm extended upward: 140-180.
             val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
-        if (elbowAngles.isEmpty() || elbowAngles.none { it in 140f..180f }) return false
-
-        // For follow-through, the arm should be high again (wrist above shoulder)
-        val shoulderPos = midpoint(landmarks, PoseLandmark.LEFT_SHOULDER, PoseLandmark.RIGHT_SHOULDER) ?: return false
-        val shoulderY = shoulderPos.second
-        val shoulderX = shoulderPos.first
-
-        val hipPos = midpoint(landmarks, PoseLandmark.LEFT_HIP, PoseLandmark.RIGHT_HIP) ?: return false
-        val hipX = hipPos.first
-
-        // Determine facing direction: if shoulder is to the right of hip, facing right (+x)
-        val facingRight = shoulderX > hipX
-
-        val leftWrist = reliable(landmarks, PoseLandmark.LEFT_WRIST)
-        val rightWrist = reliable(landmarks, PoseLandmark.RIGHT_WRIST)
-
-        // Find a wrist that is BOTH high AND in front of the shoulders
-        val validWristFound = listOfNotNull(leftWrist, rightWrist).any { wrist ->
-            val isHigh = wrist.y < shoulderY
-            val isInFront = if (facingRight) wrist.x > shoulderX else wrist.x < shoulderX
-            isHigh && isInFront
+            when {
+                torsoTilt == null -> null
+                torsoTilt > torsoTiltMaxDegrees -> "Stand up straighter"
+                torsoTilt < torsoTiltMinDegrees -> "Relax your stance slightly"
+                kneeAngles.isEmpty() -> null
+                kneeAngles.any { it < kneeAngleMinDegrees } -> "Straighten your legs"
+                elbowAngles.isEmpty() -> null
+                elbowAngles.any { it > elbowAngleMaxDegrees } -> "Bring the ball in closer to your body"
+                elbowAngles.any { it < elbowAngleMinDegrees } -> "Relax your arms a little"
+                else -> null
+            }
+        }
+        BowlingPhase.PUSHAWAY -> {
+            val torsoTilt = metrics.torsoTiltDegrees
+            val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
+            val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
+            when {
+                torsoTilt == null -> null
+                torsoTilt < 5f -> "Lean forward slightly as you push away"
+                torsoTilt > 25f -> "Don't lean too far forward yet"
+                kneeAngles.isEmpty() -> null
+                kneeAngles.any { it < 145f } -> "Keep your legs mostly straight here"
+                elbowAngles.isEmpty() -> null
+                elbowAngles.none { it in 130f..180f } -> "Push the ball further out"
+                else -> null
+            }
+        }
+        BowlingPhase.SLIDE_AND_RELEASE -> {
+            val torsoTilt = metrics.torsoTiltDegrees
+            val kneeAngles = listOfNotNull(metrics.leftKneeAngleDegrees, metrics.rightKneeAngleDegrees)
+            val elbowAngles = listOfNotNull(metrics.leftElbowAngleDegrees, metrics.rightElbowAngleDegrees)
+            when {
+                torsoTilt == null -> null
+                torsoTilt < 15f -> "Bend forward more into the slide"
+                torsoTilt > 45f -> "Don't lean in too far"
+                kneeAngles.isEmpty() -> null
+                kneeAngles.none { it in 90f..150f } -> "Bend your sliding knee more"
+                elbowAngles.isEmpty() -> null
+                elbowAngles.none { it in 150f..180f } -> "Extend your swing arm fully"
+                else -> null
+            }
+        }
+        else -> null
     }
 
-        if (!validWristFound) return false
+    companion object {
+        /**
+         * @brief The phases a bowler holds still in long enough for
+         *        frame-by-frame angle correction to be meaningful -- see
+         *        [correctionFor]'s doc for why the rest are excluded.
+         */
+        private val STATIONARY_PHASES = setOf(
+            BowlingPhase.STARTING_STANCE,
+            BowlingPhase.PUSHAWAY,
+            BowlingPhase.SLIDE_AND_RELEASE,
+        )
 
-        return true
+        /**
+         * @brief Maps a 5-step approach step count (0..5) to its corresponding [BowlingPhase].
+         *
+         * step 0 -> STARTING_STANCE
+         * step 1 -> APPROACH
+         * step 2 -> PUSHAWAY
+         * step 3 -> BACK_SWING
+         * step 4 -> POWER_STEP
+         * step 5 -> SLIDE_AND_RELEASE
+         */
+        fun phaseForStep(stepCount: Int): BowlingPhase = when {
+            stepCount <= 0 -> BowlingPhase.STARTING_STANCE
+            stepCount == 1 -> BowlingPhase.APPROACH
+            stepCount == 2 -> BowlingPhase.PUSHAWAY
+            stepCount == 3 -> BowlingPhase.BACK_SWING
+            stepCount == 4 -> BowlingPhase.POWER_STEP
+            else -> BowlingPhase.SLIDE_AND_RELEASE
+        }
+
+        /**
+         * @brief Maps a [BowlingPhase] to its corresponding 5-step approach step count.
+         */
+        @Suppress("unused")
+        fun stepForPhase(phase: BowlingPhase): Int = when (phase) {
+            BowlingPhase.STARTING_STANCE -> 0
+            BowlingPhase.APPROACH -> 1
+            BowlingPhase.PUSHAWAY -> 2
+            BowlingPhase.BACK_SWING -> 3
+            BowlingPhase.POWER_STEP -> 4
+            BowlingPhase.SLIDE_AND_RELEASE -> 5
+        }
     }
 
     /**
@@ -369,10 +464,10 @@ class PosePhaseDetector {
      *        shoulder-midpoint-to-hip-midpoint vector.
      *
      * @param landmarks Smoothed landmarks for this frame.
-     * @return The tilt in degrees, or null if we can't see the shoulders or hips.
+     * @return The tilt in degrees (always >= 0, direction-agnostic), or
+     *         null if neither shoulder or neither hip is reliably detected.
      */
     private fun torsoTiltDegrees(landmarks: Map<Int, SmoothedLandmark>): Float? {
-        // Find the middle of the shoulders and the middle of the hips.
         val shoulderMid = midpoint(landmarks, PoseLandmark.LEFT_SHOULDER, PoseLandmark.RIGHT_SHOULDER) ?: return null
         val hipMid = midpoint(landmarks, PoseLandmark.LEFT_HIP, PoseLandmark.RIGHT_HIP) ?: return null
         val dx = shoulderMid.first - hipMid.first
@@ -384,36 +479,33 @@ class PosePhaseDetector {
     }
 
     /**
-     * // Calculate the angle of a knee.
-     * @param landmarks The smoothed points of the body.
-     * @param hipType Which hip to look at.
-     * @param kneeType Which knee to look at.
-     * @param ankleType Which ankle to look at.
-     * @return The angle in degrees, or null if the camera missed a part.
+     * @brief Hip-knee-ankle angle for one leg, gated by confidence.
+     * @param landmarks Smoothed landmarks for this frame.
+     * @param hipType Landmark type constant for that leg's hip.
+     * @param kneeType Landmark type constant for that leg's knee.
+     * @param ankleType Landmark type constant for that leg's ankle.
+     * @return The angle in degrees, or null if any of the three landmarks isn't reliably detected.
      */
     private fun kneeAngle(landmarks: Map<Int, SmoothedLandmark>, hipType: Int, kneeType: Int, ankleType: Int): Float? {
-        // Try to get the hip, knee, and ankle from the camera data.
         val hip = reliable(landmarks, hipType) ?: return null
         val knee = reliable(landmarks, kneeType) ?: return null
         val ankle = reliable(landmarks, ankleType) ?: return null
-        // Calculate the angle between those three points.
         return PoseAngleCalculator.calculateAngle(hip, knee, ankle)
     }
 
     /**
-     * @brief Find the middle point between two body parts.
+     * @brief Midpoint of two landmarks, gated by confidence, falling back to
+     *        whichever single one is reliable if only one is.
      * @param landmarks Smoothed landmarks for this frame.
      * @param firstType Landmark type constant for the first side.
      * @param secondType Landmark type constant for the second side.
-     * @return The middle (x, y), or null if the camera missed both.
+     * @return The midpoint as (x, y), or null if neither landmark is reliable.
      */
     private fun midpoint(landmarks: Map<Int, SmoothedLandmark>, firstType: Int, secondType: Int): Pair<Float, Float>? {
         val first = reliable(landmarks, firstType)
         val second = reliable(landmarks, secondType)
         return when {
-            // If we have both parts, find the average.
             first != null && second != null -> (first.x + second.x) / 2f to (first.y + second.y) / 2f
-            // If we only have one, just use that one.
             first != null -> first.x to first.y
             second != null -> second.x to second.y
             else -> null
@@ -424,11 +516,10 @@ class PosePhaseDetector {
      * @brief Looks up one landmark, gated by [PoseSkeletonRenderer.MIN_LIKELIHOOD].
      * @param landmarks Smoothed landmarks for this frame.
      * @param type Landmark type constant to look up.
-     * @return The landmark, or null if it's missing or blurry.
+     * @return The landmark, or null if missing or below the confidence bar.
      */
     private fun reliable(landmarks: Map<Int, SmoothedLandmark>, type: Int): SmoothedLandmark? {
         val landmark = landmarks[type] ?: return null
-        // Only return if the camera is sure enough about where the part is.
         return landmark.takeIf { it.inFrameLikelihood >= PoseSkeletonRenderer.MIN_LIKELIHOOD }
     }
 }

docs/proposal.md

@@ -5,11 +5,30 @@
 ## Suggested sections to include
 
 - Problem statement / motivation
+Provide an app for users to improve their bowling by learning hwo to get into the correct positions.
 - Target users
+Anyone who is able to bowl
 - Proposed solution and key features
+Able to see their mistakes
+Able to see instructions on how to correct their mistakes
+Able to hear instructions on how to correct their mistakes
+Able to see the ideal form 
 - Scope (in-scope vs. out-of-scope for this project)
+Five step bowling only
+Right handed bowling only
+Starting position correction and finishing position only
 - Success criteria
+User is able to get into the correct position with help from the app
 - Team members and roles
+Lu Yong Wei (Product Owner)
+Gabriel Low (Programmer/ Version control manager)
+Harine S/O Sumen (Tech Lead)			
+Liu Jingwen	(Programmer/ Serialization manager)
+Auvik Kumar Biswas (Programmer/ Feedback manager)			
+Chan Qi Ying (Programmer/ UI lead)
+Low Yu Sheng Javier (Product Manager)	
+Khalil Belabadia (Programmer/ Audio Lead) 		
+
 
 ## Working summary (placeholder, derived from the current codebase — replace with the real proposal)