Motor sound: more presets, per-option preview, polish

- 9 new synth presets: Boxer 6, Inline-6 (silky), Tractor, Steam
  locomotive, Lightsaber, Jet turbine, UFO hover, F1 electric whine,
  Hover bike.
- 4 new sampled presets (CC0 from BigSoundBank): Helicopter, Tractor,
  Lawn mower, Steam locomotive.
- Per-option preview buttons on the Muffler and Gearbox rows. Tapping
  the inline play button triggers a 2.5s preview with that option
  applied without changing the current selection.
- previewProfile now takes optional volume / muffler / gearbox
  overrides, and SettingsViewModel snapshots current settings so the
  engine-type preview honors the Engine volume slider.
- Drop the cyan source-tag color in the engine combobox; use
  onSurfaceVariant so it sits behind the selected name.
- Rename "Virtual gearbox" to "Gearbox".
- Rewrite the engine-sound hint to focus on speed + load mapping; drop
  the audio-channel sentence.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: eried

app/src/main/java/com/eried/eucplanet/audio/EngineProfile.kt

@@ -176,6 +176,58 @@ data class EngineProfile(
                 decelPopProbability = 0.2f,
                 compressionTone = 0.45f
             ),
+            // --- Extra ICE flavors ---
+            EngineProfile(
+                key = "BOXER_6",
+                displayName = "Boxer 6",
+                kind = Kind.ICE,
+                idleRpm = 850, maxRpm = 7800,
+                cylinderCount = 6,
+                // Flat-6 firing pattern (Porsche-ish): even 120° steps in 720° cycle
+                firingAngles = floatArrayOf(0f, 120f, 240f, 360f, 480f, 600f),
+                harmonics = floatArrayOf(1f, 0.55f, 0.45f, 0.28f, 0.18f, 0.1f),
+                exhaustGrit = 0.18f,
+                decelPopProbability = 0.45f,
+                compressionTone = 0.5f
+            ),
+            EngineProfile(
+                key = "INLINE_6_SILKY",
+                displayName = "Inline-6 (silky)",
+                kind = Kind.ICE,
+                idleRpm = 700, maxRpm = 7000,
+                cylinderCount = 6,
+                firingAngles = floatArrayOf(0f, 120f, 240f, 360f, 480f, 600f),
+                harmonics = floatArrayOf(1f, 0.8f, 0.6f, 0.42f, 0.28f, 0.17f),
+                exhaustGrit = 0.08f,
+                decelPopProbability = 0.25f,
+                compressionTone = 0.4f
+            ),
+            EngineProfile(
+                key = "TRACTOR",
+                displayName = "Tractor",
+                kind = Kind.ICE, gearless = true,
+                idleRpm = 450, maxRpm = 2400,
+                cylinderCount = 1,
+                firingAngles = floatArrayOf(0f),
+                harmonics = floatArrayOf(1f, 0.9f, 0.75f, 0.55f, 0.35f, 0.2f),
+                exhaustGrit = 0.5f,
+                decelPopProbability = 0.55f,
+                compressionTone = 0.95f
+            ),
+            EngineProfile(
+                key = "STEAM_LOCO",
+                displayName = "Steam locomotive",
+                kind = Kind.ICE, gearless = true,
+                idleRpm = 180, maxRpm = 900,
+                cylinderCount = 2,
+                // Two cylinders firing 180° apart — that's the classic "chuff-chuff"
+                firingAngles = floatArrayOf(0f, 180f),
+                twoStroke = true,
+                harmonics = floatArrayOf(1f, 0.95f, 0.85f, 0.7f, 0.5f, 0.3f),
+                exhaustGrit = 0.7f,
+                decelPopProbability = 0.0f,
+                compressionTone = 0.9f
+            ),
             // --- Synth / futuristic (gearless) ---
             EngineProfile(
                 key = "TRON_WHINE",
@@ -199,6 +251,61 @@ data class EngineProfile(
                 exhaustGrit = 0.45f,
                 decelPopProbability = 0.0f
             ),
+            EngineProfile(
+                key = "LIGHTSABER",
+                displayName = "Lightsaber",
+                kind = Kind.SYNTH, gearless = true,
+                idleRpm = 300, maxRpm = 1800,
+                synthBaseHz = 55f, synthMaxHz = 220f,
+                synthShape = 0,           // sine — pure hum
+                synthFmDepth = 0.75f,     // heavy modulation gives the wobble
+                exhaustGrit = 0.02f,
+                decelPopProbability = 0.0f
+            ),
+            EngineProfile(
+                key = "JET_TURBINE",
+                displayName = "Jet turbine",
+                kind = Kind.SYNTH, gearless = true,
+                idleRpm = 1500, maxRpm = 18000,
+                synthBaseHz = 180f, synthMaxHz = 3800f,
+                synthShape = 2,           // square — bright whine
+                synthFmDepth = 0.08f,     // tight, only a touch of warble
+                exhaustGrit = 0.55f,      // turbine air hiss
+                decelPopProbability = 0.0f
+            ),
+            EngineProfile(
+                key = "UFO_HOVER",
+                displayName = "UFO hover",
+                kind = Kind.SYNTH, gearless = true,
+                idleRpm = 700, maxRpm = 3200,
+                synthBaseHz = 95f, synthMaxHz = 460f,
+                synthShape = 0,           // sine
+                synthFmDepth = 1.0f,      // huge wobble — the cliche flying-saucer warble
+                exhaustGrit = 0.1f,
+                decelPopProbability = 0.0f
+            ),
+            EngineProfile(
+                key = "F1_ELECTRIC",
+                displayName = "F1 electric whine",
+                kind = Kind.SYNTH, gearless = true,
+                idleRpm = 800, maxRpm = 20000,
+                synthBaseHz = 220f, synthMaxHz = 5200f,
+                synthShape = 1,           // saw — rich harmonic content
+                synthFmDepth = 0.04f,
+                exhaustGrit = 0.0f,
+                decelPopProbability = 0.0f
+            ),
+            EngineProfile(
+                key = "HOVER_BIKE",
+                displayName = "Hover bike",
+                kind = Kind.SYNTH, gearless = true,
+                idleRpm = 500, maxRpm = 7000,
+                synthBaseHz = 90f, synthMaxHz = 1400f,
+                synthShape = 1,           // saw + sine FM = thick mid
+                synthFmDepth = 0.35f,
+                exhaustGrit = 0.25f,
+                decelPopProbability = 0.0f
+            ),
             // --- Sampled (real recordings, all CC0 from BigSoundBank — see Credits) ---
             // For sampled engines the procedural [kind] flags below are unused; the SampledEnginePlayer
             // handles render. Idle/max RPM still drive the playback-speed mapping.
@@ -236,6 +343,35 @@ data class EngineProfile(
                 kind = Kind.ICE, gearless = true,
                 idleRpm = 850, maxRpm = 6000,
                 sampleAssetBase = "engine_citycar_saxo"
+            ),
+            EngineProfile(
+                key = "SAMPLED_HELICOPTER",
+                displayName = "Helicopter (sampled)",
+                kind = Kind.ICE, gearless = true,
+                // Helicopter rotor "RPM" is metaphorical here — drives playback speed mapping
+                idleRpm = 250, maxRpm = 1100,
+                sampleAssetBase = "engine_helicopter"
+            ),
+            EngineProfile(
+                key = "SAMPLED_TRACTOR",
+                displayName = "Tractor (sampled)",
+                kind = Kind.ICE, gearless = true,
+                idleRpm = 600, maxRpm = 2600,
+                sampleAssetBase = "engine_tractor"
+            ),
+            EngineProfile(
+                key = "SAMPLED_LAWNMOWER",
+                displayName = "Lawn mower (sampled)",
+                kind = Kind.ICE, gearless = true,
+                idleRpm = 1800, maxRpm = 3600,
+                sampleAssetBase = "engine_lawnmower"
+            ),
+            EngineProfile(
+                key = "SAMPLED_STEAM_LOCO",
+                displayName = "Steam locomotive (sampled)",
+                kind = Kind.ICE, gearless = true,
+                idleRpm = 200, maxRpm = 900,
+                sampleAssetBase = "engine_steam_loco"
             )
         )
 

app/src/main/java/com/eried/eucplanet/audio/EngineSoundEngine.kt

@@ -122,10 +122,28 @@ class EngineSoundEngine @Inject constructor(
         voiceActive = active
     }
 
-    /** Live preview while user is on the settings page (no telemetry yet). */
-    fun previewProfile(key: String, durationMs: Long = 2500L) {
-        val saved = profile
+    /**
+     * Live preview while user is on the settings page (no telemetry yet).
+     *
+     * Optional overrides let the caller A/B-test a specific knob (volume slider,
+     * muffler/gearbox option) without committing the change first. When null,
+     * the engine's current state (last [applySettings]) is used.
+     */
+    fun previewProfile(
+        key: String,
+        durationMs: Long = 2500L,
+        volume: Float? = null,
+        muffler: String? = null,
+        gearbox: String? = null
+    ) {
+        val savedProfile = profile
+        val savedVolume = masterVolume
+        val savedMuffler = mufflerKey
+        val savedGearbox = gearboxKey
         profile = EngineProfile.byKey(key)
+        if (volume != null) masterVolume = volume.coerceIn(0f, 1f)
+        if (muffler != null) mufflerKey = muffler
+        if (gearbox != null) gearboxKey = gearbox
         // Synthesize a small acceleration sweep: idle → mid → idle
         Thread {
             try {
@@ -145,7 +163,10 @@ class EngineSoundEngine @Inject constructor(
                 Thread.sleep(250)
                 stop()
             } finally {
-                profile = saved
+                profile = savedProfile
+                masterVolume = savedVolume
+                mufflerKey = savedMuffler
+                gearboxKey = savedGearbox
             }
         }.start()
     }

app/src/main/java/com/eried/eucplanet/ui/settings/SettingsScreen.kt

@@ -1951,7 +1951,8 @@ private fun EngineSoundSection(
                 "MUFFLED" to stringResource(R.string.engine_muffler_muffled)
             ),
             current = settings.engineMuffler,
-            onChange = { viewModel.updateEngineMuffler(it) }
+            onChange = { viewModel.updateEngineMuffler(it) },
+            onPreview = { viewModel.previewMufflerOption(it) }
         )
 
         SegmentedChoice(
@@ -1962,7 +1963,8 @@ private fun EngineSoundSection(
                 "SIX" to stringResource(R.string.engine_gearbox_six)
             ),
             current = settings.engineGearbox,
-            onChange = { viewModel.updateEngineGearbox(it) }
+            onChange = { viewModel.updateEngineGearbox(it) },
+            onPreview = { viewModel.previewGearboxOption(it) }
         )
 
         SegmentedChoice(
@@ -2087,7 +2089,7 @@ private fun EngineTypePicker(
                     Text(
                         sourceLabel,
                         style = MaterialTheme.typography.labelSmall,
-                        color = MaterialTheme.colorScheme.primary
+                        color = MaterialTheme.colorScheme.onSurfaceVariant
                     )
                 },
                 trailingIcon = { ExposedDropdownMenuDefaults.TrailingIcon(expanded = expanded) },
@@ -2212,7 +2214,8 @@ private fun SegmentedChoice(
     label: String,
     options: List<Pair<String, String>>,
     current: String,
-    onChange: (String) -> Unit
+    onChange: (String) -> Unit,
+    onPreview: ((String) -> Unit)? = null
 ) {
     Column(modifier = Modifier.padding(vertical = 4.dp)) {
         Text(
@@ -2232,7 +2235,13 @@ private fun SegmentedChoice(
                     selected = current == key,
                     onClick = { onChange(key) },
                     shape = SegmentedButtonDefaults.itemShape(index = index, count = options.size),
-                    icon = {},
+                    // When onPreview is wired, the leading icon slot becomes a per-option ▶ button.
+                    // IconButton consumes the click, so the SegmentedButton onChange doesn't fire.
+                    icon = {
+                        if (onPreview != null) {
+                            PlayButton(onClick = { onPreview(key) })
+                        }
+                    },
                     label = {
                         Text(
                             optLabel,

app/src/main/java/com/eried/eucplanet/ui/settings/SettingsViewModel.kt

@@ -131,7 +131,41 @@ class SettingsViewModel @Inject constructor(
     fun markEngineSafetyShown() = update { copy(engineSafetyShown = true) }
 
     fun previewEngine(key: String) {
-        engineSoundEngine.previewProfile(key)
+        viewModelScope.launch {
+            val s = settingsRepository.get()
+            engineSoundEngine.previewProfile(
+                key = key,
+                volume = s.engineVolume,
+                muffler = s.engineMuffler,
+                gearbox = s.engineGearbox
+            )
+        }
+    }
+
+    /** Preview the currently selected engine with [mufflerOverride] applied — for the per-option ▶ buttons. */
+    fun previewMufflerOption(mufflerOverride: String) {
+        viewModelScope.launch {
+            val s = settingsRepository.get()
+            engineSoundEngine.previewProfile(
+                key = s.engineType,
+                volume = s.engineVolume,
+                muffler = mufflerOverride,
+                gearbox = s.engineGearbox
+            )
+        }
+    }
+
+    /** Preview the currently selected engine with [gearboxOverride] applied — for the per-option ▶ buttons. */
+    fun previewGearboxOption(gearboxOverride: String) {
+        viewModelScope.launch {
+            val s = settingsRepository.get()
+            engineSoundEngine.previewProfile(
+                key = s.engineType,
+                volume = s.engineVolume,
+                muffler = s.engineMuffler,
+                gearbox = gearboxOverride
+            )
+        }
     }
     fun updateAutoRecord(v: Boolean) = update { copy(autoRecord = v) }
     fun updateAutoRecordStartInMotion(v: Boolean) = update { copy(autoRecordStartInMotion = v) }

app/src/main/res/raw/engine_helicopter.ogg

@@ -242,7 +242,7 @@
     <!-- Motor sound generator -->
     <string name="section_engine_sound">Motor sound</string>
     <string name="engine_sound_enabled">Engine sound</string>
-    <string name="engine_sound_enabled_hint">Synthesised engine driven by your wheel\'s speed and load. Plays through the media channel so it mixes with music.</string>
+    <string name="engine_sound_enabled_hint">Drives engine RPM in real time from your wheel\'s speed and motor load. Higher load pushes the revs up, coasting and regen pull them back.</string>
     <string name="engine_safety_title">Heads up</string>
     <string name="engine_safety_message">Engine sound can mask traffic noise. Use lower volumes in city riding, and consider a single-ear headphone so you stay aware of your surroundings.</string>
     <string name="engine_safety_ok">Got it</string>
@@ -255,7 +255,7 @@
     <string name="engine_muffler_open">Open</string>
     <string name="engine_muffler_half">Half</string>
     <string name="engine_muffler_muffled">Muffled</string>
-    <string name="engine_gearbox_label">Virtual gearbox</string>
+    <string name="engine_gearbox_label">Gearbox</string>
     <string name="engine_gearbox_off">Off</string>
     <string name="engine_gearbox_four">4-speed</string>
     <string name="engine_gearbox_six">6-speed</string>
@@ -286,13 +286,26 @@
     <string name="engine_preset_v8_muscle">V8 muscle</string>
     <string name="engine_preset_v12_italian">V12 Italian</string>
     <string name="engine_preset_v16_luxury">V16 luxury</string>
+    <string name="engine_preset_boxer_6">Boxer 6</string>
+    <string name="engine_preset_inline_6_silky">Inline-6 (silky)</string>
+    <string name="engine_preset_tractor">Tractor</string>
+    <string name="engine_preset_steam_loco">Steam locomotive</string>
     <string name="engine_preset_tron_whine">Tron whine</string>
     <string name="engine_preset_pod_racer">Pod racer</string>
+    <string name="engine_preset_lightsaber">Lightsaber</string>
+    <string name="engine_preset_jet_turbine">Jet turbine</string>
+    <string name="engine_preset_ufo_hover">UFO hover</string>
+    <string name="engine_preset_f1_electric">F1 electric whine</string>
+    <string name="engine_preset_hover_bike">Hover bike</string>
     <string name="engine_preset_sampled_v8_cobra">V8 Cobra</string>
     <string name="engine_preset_sampled_vtwin_ducati">V-twin Ducati</string>
     <string name="engine_preset_sampled_diesel_iveco">Diesel truck</string>
     <string name="engine_preset_sampled_motorcycle">Motorcycle</string>
     <string name="engine_preset_sampled_city_car">City car</string>
+    <string name="engine_preset_sampled_helicopter">Helicopter</string>
+    <string name="engine_preset_sampled_tractor">Tractor</string>
+    <string name="engine_preset_sampled_lawnmower">Lawn mower</string>
+    <string name="engine_preset_sampled_steam_loco">Steam locomotive</string>
 
     <string name="col_periodic">Periodic</string>
     <string name="col_trigger">Trigger</string>