Document pokedex cry screen

2 files changed, 215 insertions, 166 deletions

diff --git a/src/pokedex.c b/src/pokedex.c
index 7532f0c99..ba05969ae 100644
--- a/src/pokedex.c
+++ b/src/pokedex.c
@@ -3568,14 +3568,14 @@ static void Task_LoadCryScreen(u8 taskId)
         break;
     case 6:
         {
-            struct CryRelatedStruct sp4;
-
-            sp4.unk0 = 0x4020;
-            sp4.unk2 = 0x1F;
-            sp4.paletteNo = 8;
-            sp4.yPos = 0x1E;
-            sp4.xPos = 0xC;
-            if (LoadCryWaveformWindow(&sp4, 2))
+            struct CryScreenWindow waveformWindow;
+
+            waveformWindow.unk0 = 0x4020;
+            waveformWindow.unk2 = 31;
+            waveformWindow.paletteNo = 8;
+            waveformWindow.yPos = 30;
+            waveformWindow.xPos = 12;
+            if (LoadCryWaveformWindow(&waveformWindow, 2))
             {
                 gMain.state++;
                 gDexCryScreenState = 0;
@@ -3584,12 +3584,12 @@ static void Task_LoadCryScreen(u8 taskId)
         break;
     case 7:
         {
-            struct CryRelatedStruct spC;
+            struct CryScreenWindow cryMeter;
 
-            spC.paletteNo = 9;
-            spC.xPos = 0x12;
-            spC.yPos = 3;
-            if (LoadCryMeter(&spC, 3))
+            cryMeter.paletteNo = 9;
+            cryMeter.xPos = 18;
+            cryMeter.yPos = 3;
+            if (LoadCryMeter(&cryMeter, 3))
                 gMain.state++;
             CopyWindowToVram(WIN_VU_METER, 2);
             CopyWindowToVram(WIN_INFO, 3);
diff --git a/src/pokedex_cry_screen.c b/src/pokedex_cry_screen.c
index 02ce18d05..0a6f639ae 100644
--- a/src/pokedex_cry_screen.c
+++ b/src/pokedex_cry_screen.c
@@ -9,35 +9,53 @@
 #include "trig.h"
 #include "window.h"
 
-struct PokedexCryVolumeMeter {
-    s8 unk0;
-    s8 unk1;
-    u8 unk2;
-    u16 needleSpriteId;
+// Cry meter needle positions
+//
+//          0
+//    32   .  .  -32
+//      .        .
+// 64  .          . -64
+//     .          .
+//      .        .
+//    96   .  .  -96
+//         127
+//   
+#define MIN_NEEDLE_POS  32
+#define MAX_NEEDLE_POS -32
+
+#define NEEDLE_MOVE_INCREMENT  5
+
+#define WAVEFORM_WINDOW_HEIGHT 56
+
+struct PokedexCryMeterNeedle {
+    s8 rotation;
+    s8 targetRotation;
+    u8 moveIncrement;
+    u16 spriteId;
 };
 
 struct PokedexCryScreen
 {
-    u8 unk0[16];
-    u8 unk10;
-    u8 unk11;
-    u8 unk12;
-    u16 unk14;
-    u8 unk16;
+    u8 cryWaveformBuffer[16];
+    u8 cryState;
+    u8 playhead;
+    u8 waveformPreviousY;
+    u16 unk; // Never read
+    u8 playStartPos;
     u16 species;
-    u8 unk1A;
-    u8 unk1B;
+    u8 cryOverrideCountdown;
+    u8 cryRepeatDelay;
 };
 
 static void PlayCryScreenCry(u16);
-static void sub_81455A8(void);
+static void BufferCryWaveformSegment(void);
 static void DrawWaveformFlatline(void);
-static void sub_8145648(u8);
+static void AdvancePlayhead(u8);
 static void DrawWaveformSegment(u8, u8);
-static void sub_8145814(u8);
-static void sub_8145824(u8, s16, u8);
+static void DrawWaveformWindow(u8);
+static void ShiftWaveformOver(u8, s16, bool8);
 static void SpriteCB_CryMeterNeedle(struct Sprite *);
-static void sub_8145B24(s8);
+static void SetCryMeterNeedleTarget(s8);
 
 // IWRAM common
 u8 gDexCryScreenState;
@@ -45,7 +63,7 @@ u8 gDexCryScreenState;
 // EWRAM vars
 static EWRAM_DATA struct PokedexCryScreen *sDexCryScreen = NULL;
 static EWRAM_DATA u8 *sCryWaveformWindowTiledata = NULL;
-static EWRAM_DATA struct PokedexCryVolumeMeter *sCryVolumeMeter = NULL;
+static EWRAM_DATA struct PokedexCryMeterNeedle *sCryMeterNeedle = NULL;
 
 static const u16 sCryMeterNeedle_Pal[] = INCBIN_U16("graphics/pokedex/cry_meter_needle.gbapal");
 static const u8 sCryMeterNeedle_Gfx[] = INCBIN_U8("graphics/pokedex/cry_meter_needle.4bpp");
@@ -54,7 +72,7 @@ static const u16 sCryMeter_Tilemap[] = INCBIN_U16("graphics/pokedex/cry_meter_ma
 static const u16 sCryMeter_Pal[] = INCBIN_U16("graphics/pokedex/cry_meter.gbapal");
 static const u8 sCryMeter_Gfx[] = INCBIN_U8("graphics/pokedex/cry_meter.4bpp.lz");
 
-const u16 gUnknown_085B8770[][72] =
+static const u16 sWaveformOffsets[][72] =
 {
     {
         0x0000, 0x0004, 0x0008, 0x000C, 0x0010, 0x0014, 0x0018, 0x001C,
@@ -139,18 +157,21 @@ const u16 gUnknown_085B8770[][72] =
     }
 };
 
-static const u16 sCryScreenBg_Pal[] = INCBIN_U16("graphics/pokedex/85B8C10.gbapal");
-static const u8 sCryScreenBg_Gfx[] = INCBIN_U8("graphics/pokedex/85B8C10.4bpp");
+static const u16 sCryScreenBg_Pal[] = INCBIN_U16("graphics/pokedex/cry_screen_bg.gbapal");
+static const u8 sCryScreenBg_Gfx[] = INCBIN_U8("graphics/pokedex/cry_screen_bg.4bpp");
 
-const u8 gUnknown_085B8C30[] = {0xF0, 0x0F};
-const u8 gUnknown_085B8C32[][16] =
+static const u8 sWaveformTileDataNybbleMasks[] = {0xF0, 0x0F};
+
+// Waveform is blue in the middle (8) grading to white at peaks (15)
+// Split into two arrays for the two vertical slice halves
+static const u8 sWaveformColor[][16] =
 {
     {
-        0x0F, 0x0E, 0x0D, 0x0C, 0x0B, 0x0A, 0x09, 0x08,
-        0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
+        15,      14,      13,      12,      11,      10,       9,       8,
+         8,       9,      10,      11,      12,      13,      14,      15,
     }, {
-        0xF0, 0xE0, 0xD0, 0xC0, 0xB0, 0xA0, 0x90, 0x80,
-        0x80, 0x90, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0
+        15 << 4, 14 << 4, 13 << 4, 12 << 4, 11 << 4, 10 << 4,  9 << 4,  8 << 4,
+         8 << 4,  9 << 4, 10 << 4, 11 << 4, 12 << 4, 13 << 4, 14 << 4, 15 << 4,
     }
 };
 
@@ -202,7 +223,7 @@ static const struct SpritePalette sCryMeterNeedleSpritePalettes[] =
     {}
 };
 
-bool8 LoadCryWaveformWindow(struct CryRelatedStruct *arg0, u8 windowId)
+bool8 LoadCryWaveformWindow(struct CryScreenWindow *window, u8 windowId)
 {
     u8 i;
     u8 finished = FALSE;
@@ -216,28 +237,28 @@ bool8 LoadCryWaveformWindow(struct CryRelatedStruct *arg0, u8 windowId)
             sCryWaveformWindowTiledata = (u8*)GetWindowAttribute(windowId, WINDOW_TILE_DATA);
         }
 
-        sDexCryScreen->unk14 = arg0->unk0;
-        sDexCryScreen->unk16 = arg0->yPos;
-        sDexCryScreen->unk1A = 0;
-        sDexCryScreen->unk1B = 0;
-        sDexCryScreen->unk10 = 0;
-        sDexCryScreen->unk12 = 28;
-        sDexCryScreen->unk11 = 0;
-        sub_8145824(windowId, -8 * arg0->xPos, 1);
+        sDexCryScreen->unk = window->unk0;
+        sDexCryScreen->playStartPos = window->yPos;
+        sDexCryScreen->cryOverrideCountdown = 0;
+        sDexCryScreen->cryRepeatDelay = 0;
+        sDexCryScreen->cryState = 0;
+        sDexCryScreen->waveformPreviousY = WAVEFORM_WINDOW_HEIGHT / 2;
+        sDexCryScreen->playhead = 0;
+        ShiftWaveformOver(windowId, -8 * window->xPos, TRUE); // Does nothing
         for (i = 0; i < 224; i++)
             CopyToWindowPixelBuffer(windowId, sCryScreenBg_Gfx, TILE_SIZE_4BPP, i);
 
         gDexCryScreenState++;
         break;
     case 1:
-        for (i = 0; i < sDexCryScreen->unk16 * 8; i++)
+        for (i = 0; i < sDexCryScreen->playStartPos * 8; i++)
             DrawWaveformSegment(i, 0);
         
         gDexCryScreenState++;
         break;
     case 2:
-        sub_8145814(windowId);
-        LoadPalette(sCryScreenBg_Pal, arg0->paletteNo * 16, 32);
+        DrawWaveformWindow(windowId);
+        LoadPalette(sCryScreenBg_Pal, window->paletteNo * 16, 32);
         finished = TRUE;
         break;
     }
@@ -247,17 +268,20 @@ bool8 LoadCryWaveformWindow(struct CryRelatedStruct *arg0, u8 windowId)
 
 void UpdateCryWaveformWindow(u8 windowId)
 {
-    u8 var0;
+    u8 waveformIdx;
+
+    DrawWaveformWindow(windowId);
+    AdvancePlayhead(windowId);
 
-    sub_8145814(windowId);
-    sub_8145648(windowId);
-    if (sDexCryScreen->unk1B)
-        sDexCryScreen->unk1B--;
+    // Cry cant be replayed until this counter is done
+    if (sDexCryScreen->cryRepeatDelay)
+        sDexCryScreen->cryRepeatDelay--;
 
-    if (sDexCryScreen->unk1A)
+    // Once a cry replay has started, it waits for this countdown before playing
+    if (sDexCryScreen->cryOverrideCountdown)
     {
-        sDexCryScreen->unk1A--;
-        if (!sDexCryScreen->unk1A)
+        sDexCryScreen->cryOverrideCountdown--;
+        if (!sDexCryScreen->cryOverrideCountdown)
         {
             PlayCryScreenCry(sDexCryScreen->species);
             DrawWaveformFlatline();
@@ -265,47 +289,51 @@ void UpdateCryWaveformWindow(u8 windowId)
         }
     }
 
-    if (sDexCryScreen->unk10 == 0)
+    // No cry playing
+    if (sDexCryScreen->cryState == 0)
     {
         DrawWaveformFlatline();
         return;
     }
     
-    if (sDexCryScreen->unk10 == 1)
+    // Cry playing, buffer waveform
+    if (sDexCryScreen->cryState == 1)
     {
-        sub_81455A8();
+        BufferCryWaveformSegment();
     }
-    else if (sDexCryScreen->unk10 > 8)
+    else if (sDexCryScreen->cryState > 8)
     {
+        // Buffered waveform exhausted, end or buffer more
         if (!IsCryPlaying())
         {
             DrawWaveformFlatline();
-            sDexCryScreen->unk10 = 0;
+            sDexCryScreen->cryState = 0;
             return;
         }
 
-        sub_81455A8();
-        sDexCryScreen->unk10 = 1;
+        BufferCryWaveformSegment();
+        sDexCryScreen->cryState = 1;
     }
 
-    var0 = 2 * (sDexCryScreen->unk10 - 1);
-    DrawWaveformSegment(sDexCryScreen->unk16 * 8 + sDexCryScreen->unk11 - 2, sDexCryScreen->unk0[var0]);
-    DrawWaveformSegment(sDexCryScreen->unk16 * 8 + sDexCryScreen->unk11 - 1, sDexCryScreen->unk0[var0 + 1]);
-    sDexCryScreen->unk10++;
+    // Draw cry
+    waveformIdx = 2 * (sDexCryScreen->cryState - 1);
+    DrawWaveformSegment(sDexCryScreen->playStartPos * 8 + sDexCryScreen->playhead - 2, sDexCryScreen->cryWaveformBuffer[waveformIdx]);
+    DrawWaveformSegment(sDexCryScreen->playStartPos * 8 + sDexCryScreen->playhead - 1, sDexCryScreen->cryWaveformBuffer[waveformIdx + 1]);
+    sDexCryScreen->cryState++;
 }
 
 void CryScreenPlayButton(u16 species)
 {
-    if (gMPlayInfo_BGM.status & MUSICPLAYER_STATUS_PAUSE && !sDexCryScreen->unk1A)
+    if (gMPlayInfo_BGM.status & MUSICPLAYER_STATUS_PAUSE && !sDexCryScreen->cryOverrideCountdown)
     {
-        if (!sDexCryScreen->unk1B)
+        if (!sDexCryScreen->cryRepeatDelay)
         {
-            sDexCryScreen->unk1B = 4;
+            sDexCryScreen->cryRepeatDelay = 4;
             if (IsCryPlaying() == TRUE)
             {
                 StopCry();
                 sDexCryScreen->species = species;
-                sDexCryScreen->unk1A = 2;
+                sDexCryScreen->cryOverrideCountdown = 2;
             }
             else
             {
@@ -317,11 +345,11 @@ void CryScreenPlayButton(u16 species)
 
 static void PlayCryScreenCry(u16 species)
 {
-    PlayCry2(species, 0, 0x7d, 10);
-    sDexCryScreen->unk10 = 1;
+    PlayCry2(species, 0, 125, 10);
+    sDexCryScreen->cryState = 1;
 }
 
-static void sub_81455A8(void)
+static void BufferCryWaveformSegment(void)
 {
     u8 i;
     s8 *baseBuffer;
@@ -333,102 +361,113 @@ static void sub_81455A8(void)
         baseBuffer = gSoundInfo.pcmBuffer + (gSoundInfo.pcmDmaPeriod + 1 - gPcmDmaCounter) * gSoundInfo.pcmSamplesPerVBlank;
 
     buffer = baseBuffer + 0x630;
-    for (i = 0; i < ARRAY_COUNT(sDexCryScreen->unk0); i++)
-        sDexCryScreen->unk0[i] = buffer[i * 2] * 2;
+    for (i = 0; i < ARRAY_COUNT(sDexCryScreen->cryWaveformBuffer); i++)
+        sDexCryScreen->cryWaveformBuffer[i] = buffer[i * 2] * 2;
 }
 
 static void DrawWaveformFlatline(void)
 {
-    DrawWaveformSegment(sDexCryScreen->unk16 * 8 + sDexCryScreen->unk11 - 2, 0);
-    DrawWaveformSegment(sDexCryScreen->unk16 * 8 + sDexCryScreen->unk11 - 1, 0);
+    DrawWaveformSegment(sDexCryScreen->playStartPos * 8 + sDexCryScreen->playhead - 2, 0);
+    DrawWaveformSegment(sDexCryScreen->playStartPos * 8 + sDexCryScreen->playhead - 1, 0);
 }
 
-static void sub_8145648(u8 windowId)
+static void AdvancePlayhead(u8 windowId)
 {
     u8 i;
     u16 offset;
 
-    sub_8145824(windowId, sDexCryScreen->unk11, 0);
-    sDexCryScreen->unk11 += 2;
-    offset = (sDexCryScreen->unk11 / 8 + sDexCryScreen->unk16 + 1) % 32;
+    ShiftWaveformOver(windowId, sDexCryScreen->playhead, FALSE);
+    sDexCryScreen->playhead += 2;
+    offset = (sDexCryScreen->playhead / 8 + sDexCryScreen->playStartPos + 1) % 32;
     for (i = 0; i < 7; i++)
         CopyToWindowPixelBuffer(windowId, sCryScreenBg_Gfx, TILE_SIZE_4BPP, offset + (i * TILE_SIZE_4BPP));
 }
 
-static void DrawWaveformSegment(u8 a0, u8 a1)
+// Waveform segments are drawn in alternate vertical slices
+// Note that the waveform isnt put on screen until DrawWaveformWindow
+static void DrawWaveformSegment(u8 position, u8 amplitude)
 {
-    u8 sp0;
-    u8 r6;
-    u8 r8;
-    u16 offset;
-    u16 r1;
-    u8 i;
+    // Position is a bitfield containing the play start pos, the playhead pos, and which vertical slice half to draw
+    #define PLAY_START_POS (position >> 3)
+    #define PLAYHEAD_POS   (position & ((1 << 3) - 1))
+    #define VERT_SLICE     (position & 1)
 
-    r1 = (a1 + 127) * 256;
-    i = r1 / 1152.0;
-    if (i > 55)
-        i = 55;
-    sp0 = i;
-    r6 = a0 & 1;
-    if (i > sDexCryScreen->unk12)
+    u8 currentPointY;
+    u8 nybble;
+    u16 offset;
+    u16 temp;
+    u8 y;
+
+    temp = (amplitude + 127) * 256;
+    y = temp / 1152.0;
+    if (y > WAVEFORM_WINDOW_HEIGHT - 1)
+        y = WAVEFORM_WINDOW_HEIGHT - 1;
+    currentPointY = y;
+    nybble = VERT_SLICE;
+    if (y > sDexCryScreen->waveformPreviousY)
     {
+        // Current point lower than previous point, draw point and draw line up to previous
         do
         {
-            offset = gUnknown_085B8770[a0 & 0x7][i] + (a0 / 8) * TILE_SIZE_4BPP;
-            sCryWaveformWindowTiledata[offset] &= gUnknown_085B8C30[r6];
-            sCryWaveformWindowTiledata[offset] |= gUnknown_085B8C32[r6][((i / 3) - 1) & 0x0F];
-            i--;
-        } while (i > sDexCryScreen->unk12);
+            offset = sWaveformOffsets[PLAYHEAD_POS][y] + PLAY_START_POS * TILE_SIZE_4BPP;
+            sCryWaveformWindowTiledata[offset] &= sWaveformTileDataNybbleMasks[nybble];
+            sCryWaveformWindowTiledata[offset] |= sWaveformColor[nybble][((y / 3) - 1) & 0x0F];
+            y--;
+        } while (y > sDexCryScreen->waveformPreviousY);
     }
     else
     {
+        // Current point higher than previous point, draw point and draw line down to previous
         do
         {
-            offset = gUnknown_085B8770[a0 & 0x7][i] + (a0 / 8) * TILE_SIZE_4BPP;
-            sCryWaveformWindowTiledata[offset] &= gUnknown_085B8C30[r6];
-            sCryWaveformWindowTiledata[offset] |= gUnknown_085B8C32[r6][((i / 3) - 1) & 0x0F];
-            i++;
-        } while (i < sDexCryScreen->unk12);
+            offset = sWaveformOffsets[PLAYHEAD_POS][y] + PLAY_START_POS * TILE_SIZE_4BPP;
+            sCryWaveformWindowTiledata[offset] &= sWaveformTileDataNybbleMasks[nybble];
+            sCryWaveformWindowTiledata[offset] |= sWaveformColor[nybble][((y / 3) - 1) & 0x0F];
+            y++;
+        } while (y < sDexCryScreen->waveformPreviousY);
     }
 
-    sDexCryScreen->unk12 = sp0;
+    sDexCryScreen->waveformPreviousY = currentPointY;
 }
 
-static void sub_8145814(u8 windowId)
+static void DrawWaveformWindow(u8 windowId)
 {
     CopyWindowToVram(windowId, 2);
 }
 
-static void sub_8145824(u8 windowId, s16 arg1, u8 arg2)
+// rsVertical is leftover from a very different version of this function in RS
+// In RS, when TRUE it would use VOFS and when FALSE it would use HOFS (only FALSE was used)
+// Here when TRUE it does nothing
+static void ShiftWaveformOver(u8 windowId, s16 offset, bool8 rsVertical)
 {
-    if (!arg2)
+    if (!rsVertical)
     {
         u8 bg = GetWindowAttribute(windowId, WINDOW_BG);
-        ChangeBgX(bg, arg1 << 8, 0);
+        ChangeBgX(bg, offset << 8, 0);
     }
 }
 
-bool8 LoadCryMeter(struct CryRelatedStruct *arg0, u8 windowId)
+bool8 LoadCryMeter(struct CryScreenWindow *window, u8 windowId)
 {
     bool8 finished = FALSE;
 
     switch (gDexCryScreenState)
     {
     case 0:
-        if (!sCryVolumeMeter)
-            sCryVolumeMeter = AllocZeroed(sizeof(*sCryVolumeMeter));
+        if (!sCryMeterNeedle)
+            sCryMeterNeedle = AllocZeroed(sizeof(*sCryMeterNeedle));
 
         CopyToWindowPixelBuffer(windowId, sCryMeter_Gfx, 0, 0);
-        LoadPalette(sCryMeter_Pal, arg0->paletteNo * 16, 32);
+        LoadPalette(sCryMeter_Pal, window->paletteNo * 16, 32);
         gDexCryScreenState++;
         break;
     case 1:
         LoadSpriteSheets(sCryMeterNeedleSpriteSheets);
         LoadSpritePalettes(sCryMeterNeedleSpritePalettes);
-        sCryVolumeMeter->needleSpriteId = CreateSprite(&sCryMeterNeedleSpriteTemplate, 40 + arg0->xPos * 8, 56 + arg0->yPos * 8, 1);
-        sCryVolumeMeter->unk0 = 32;
-        sCryVolumeMeter->unk1 = 32;
-        sCryVolumeMeter->unk2 = 0;
+        sCryMeterNeedle->spriteId = CreateSprite(&sCryMeterNeedleSpriteTemplate, 40 + window->xPos * 8, 56 + window->yPos * 8, 1);
+        sCryMeterNeedle->rotation = MIN_NEEDLE_POS;
+        sCryMeterNeedle->targetRotation = MIN_NEEDLE_POS;
+        sCryMeterNeedle->moveIncrement = 0;
         finished = TRUE;
         break;
     }
@@ -438,92 +477,102 @@ bool8 LoadCryMeter(struct CryRelatedStruct *arg0, u8 windowId)
 
 void FreeCryScreen(void)
 {
-    FreeSpritePaletteByTag(GetSpritePaletteTagByPaletteNum(gSprites[sCryVolumeMeter->needleSpriteId].oam.paletteNum));
-    DestroySprite(gSprites + sCryVolumeMeter->needleSpriteId);
+    FreeSpritePaletteByTag(GetSpritePaletteTagByPaletteNum(gSprites[sCryMeterNeedle->spriteId].oam.paletteNum));
+    DestroySprite(gSprites + sCryMeterNeedle->spriteId);
     FREE_AND_SET_NULL(sDexCryScreen);
-    FREE_AND_SET_NULL(sCryVolumeMeter);
+    FREE_AND_SET_NULL(sCryMeterNeedle);
 }
 
 static void SpriteCB_CryMeterNeedle(struct Sprite *sprite)
 {
     u16 i;
-    s8 r3;
+    s8 peakAmplitude;
     s16 x;
     s16 y;
     struct ObjAffineSrcData affine;
     struct OamMatrix matrix;
-    u8 *var0;
+    u8 amplitude;
 
-    gSprites[sCryVolumeMeter->needleSpriteId].oam.affineMode = ST_OAM_AFFINE_NORMAL;
-    gSprites[sCryVolumeMeter->needleSpriteId].oam.affineParam = 0;
-    switch (sDexCryScreen->unk10)
+    gSprites[sCryMeterNeedle->spriteId].oam.affineMode = ST_OAM_AFFINE_NORMAL;
+    gSprites[sCryMeterNeedle->spriteId].oam.affineParam = 0;
+
+    // While no cry is playing, cryState is 0
+    // While cry is playing, cryState loops 1-8
+    switch (sDexCryScreen->cryState)
     {
     case 0:
-        sCryVolumeMeter->unk1 = 32;
-        if (sCryVolumeMeter->unk0 > 0)
+        sCryMeterNeedle->targetRotation = MIN_NEEDLE_POS;
+        if (sCryMeterNeedle->rotation > 0)
         {
-            if (sCryVolumeMeter->unk2 != 1)
-                sCryVolumeMeter->unk2--;
+            if (sCryMeterNeedle->moveIncrement != 1)
+                sCryMeterNeedle->moveIncrement--;
         }
         else
-            sCryVolumeMeter->unk2 = 5;
+        {
+            sCryMeterNeedle->moveIncrement = NEEDLE_MOVE_INCREMENT;
+        }
         break;
     case 2:
-        r3 = 0;
-        for (i = 0; i < ARRAY_COUNT(sDexCryScreen->unk0); i++)
+        peakAmplitude = 0;
+        for (i = 0; i < ARRAY_COUNT(sDexCryScreen->cryWaveformBuffer); i++)
         {
-            if (r3 < sDexCryScreen->unk0[i])
-                r3 = sDexCryScreen->unk0[i];
+            if (peakAmplitude < sDexCryScreen->cryWaveformBuffer[i])
+                peakAmplitude = sDexCryScreen->cryWaveformBuffer[i];
         }
-        sub_8145B24(r3 * 0xd0 / 0x100);
+        SetCryMeterNeedleTarget(peakAmplitude * 208 / 256);
         break;
     case 6:
-        var0 = &sDexCryScreen->unk0[10];
-        sub_8145B24(*var0 * 0xd0 / 0x100);
+        // To introduce some randomness, needle jumps to set pos in waveform rather than peak
+        amplitude = sDexCryScreen->cryWaveformBuffer[10];
+        SetCryMeterNeedleTarget(amplitude * 208 / 256);
         break;
     }
 
-    if (sCryVolumeMeter->unk0 == sCryVolumeMeter->unk1)
+    if (sCryMeterNeedle->rotation == sCryMeterNeedle->targetRotation)
     {
-        // empty block
+        // Empty, needle has reached target
     }
-    else if (sCryVolumeMeter->unk0 < sCryVolumeMeter->unk1)
+    else if (sCryMeterNeedle->rotation < sCryMeterNeedle->targetRotation)
     {
-        sCryVolumeMeter->unk0 += sCryVolumeMeter->unk2;
-        if (sCryVolumeMeter->unk0 > sCryVolumeMeter->unk1)
+        // Rotate needle left
+        sCryMeterNeedle->rotation += sCryMeterNeedle->moveIncrement;
+        if (sCryMeterNeedle->rotation > sCryMeterNeedle->targetRotation)
         {
-            sCryVolumeMeter->unk0 = sCryVolumeMeter->unk1;
-            sCryVolumeMeter->unk1 = 0;
+            sCryMeterNeedle->rotation = sCryMeterNeedle->targetRotation;
+            sCryMeterNeedle->targetRotation = 0;
         }
     }
     else
     {
-        sCryVolumeMeter->unk0 -= sCryVolumeMeter->unk2;
-        if (sCryVolumeMeter->unk0 < sCryVolumeMeter->unk1)
+        // Rotate needle right
+        sCryMeterNeedle->rotation -= sCryMeterNeedle->moveIncrement;
+        if (sCryMeterNeedle->rotation < sCryMeterNeedle->targetRotation)
         {
-            sCryVolumeMeter->unk0 = sCryVolumeMeter->unk1;
-            sCryVolumeMeter->unk1 = 0;
+            sCryMeterNeedle->rotation = sCryMeterNeedle->targetRotation;
+            sCryMeterNeedle->targetRotation = 0;
         }
     }
 
-    affine.xScale = 0x100;
-    affine.yScale = 0x100;
-    affine.rotation = sCryVolumeMeter->unk0 * 256;
+    affine.xScale = 256;
+    affine.yScale = 256;
+    affine.rotation = sCryMeterNeedle->rotation * 256;
     ObjAffineSet(&affine, &matrix, 1, 2);
     SetOamMatrix(0, matrix.a, matrix.b, matrix.c, matrix.d);
-    x = gSineTable[((sCryVolumeMeter->unk0 + 0x7F) & 0xFF)];
-    y = gSineTable[((sCryVolumeMeter->unk0 + 0x7F) & 0xFF) + 64];
+    x = gSineTable[((sCryMeterNeedle->rotation + 0x7F) & 0xFF)];
+    y = gSineTable[((sCryMeterNeedle->rotation + 0x7F) & 0xFF) + 64];
     sprite->pos2.x = x * 24 / 256;
     sprite->pos2.y = y * 24 / 256;
 }
 
-static void sub_8145B24(s8 a0)
+static void SetCryMeterNeedleTarget(s8 offset)
 {
-    u16 r2 = (0x20 - a0) & 0xff;
-    if (r2 > 0x20 && r2 < 0xe0)
-        r2 = 0xe0;
+    u16 rotation = (MIN_NEEDLE_POS - offset) & 0xFF;
+
+    // Min is positive, max is negative. Make sure needle hasnt moved out of bounds
+    if (rotation > MIN_NEEDLE_POS && rotation < (u8)MAX_NEEDLE_POS)
+        rotation = (u8)MAX_NEEDLE_POS;
 
-    sCryVolumeMeter->unk1 = r2;
-    sCryVolumeMeter->unk2 = 5;
+    sCryMeterNeedle->targetRotation = rotation;
+    sCryMeterNeedle->moveIncrement = NEEDLE_MOVE_INCREMENT;
 }