diff --git a/Source/io/midi.c b/Source/io/midi.c
index 87f9b11..8ccdbec 100644
--- a/Source/io/midi.c
+++ b/Source/io/midi.c
@@ -23,23 +23,23 @@ void updateMidiBuffer(void) {
       return;
     }
     statusByte = byte;
-    capturedAddress = 0;
-    systemIdle = 0;
+    capturedAddress = false;
+    systemIdle = false;
     return;
   }
 
   // 2ND BYTE (note/CC control)
   if (!capturedAddress) {
-    capturedAddress = 1;
+    capturedAddress = true;
     addressByte = byte;
-    systemIdle = 0;
+    systemIdle = false;
     return;
   }
 
   // 3RD BYTE (velocity/value)
-  capturedAddress = 0;
+  capturedAddress = false;
   valueByte = byte;
-  systemIdle = 0;
+  systemIdle = false;
 
   switch ((statusByte >> 4) & 0x0F) {
   case MIDI_STATUS_PB:
diff --git a/Source/io/serial.c b/Source/io/serial.c
index 54c1df9..58c262e 100644
--- a/Source/io/serial.c
+++ b/Source/io/serial.c
@@ -16,7 +16,7 @@ void serial_isr(void) CRITICAL INTERRUPT {
   // the interrupt can happen over a vblank, and if so, no rendering should
   // happen otherwise we will get unsafe VRAM access.
   // also this prioritises updateMidiBuffer()
-  systemIdle = 0;
+  systemIdle = false;
 }
 
 ISR_VECTOR(VECTOR_SERIAL, serial_isr)
diff --git a/Source/mGB.c b/Source/mGB.c
index 75650d1..412aabd 100644
--- a/Source/mGB.c
+++ b/Source/mGB.c
@@ -73,7 +73,7 @@ void main(void) {
 inline void gameMain(void) {
   rSC = SIOF_XFER_START | SIOF_CLOCK_EXT;
   while (1) {
-    systemIdle = 1;
+    systemIdle = true;
 
     updateMidiBuffer();
 
diff --git a/Source/screen/main.c b/Source/screen/main.c
index ba60c98..e67ee40 100644
--- a/Source/screen/main.c
+++ b/Source/screen/main.c
@@ -9,7 +9,6 @@
 #include "../synth/wav.h"
 #include "screen.h"
 
-bool recallMode;
 // v 1.3.3
 const uint8_t versionnumber[10] = {32, 81, 2, 81, 4, 81, 4, 0, 0, 0};
 
@@ -261,9 +260,9 @@ void setCursor(void) {
       cursorColumn = LAST_COL;
     if (cursorColumn > LAST_COL)
       cursorColumn = 0;
-    cursorEnable[cursorColumn] = 1U;
+    cursorEnable[cursorColumn] = true;
     if (!shiftSelect) {
-      cursorEnable[cursorColumnLast] = 0U;
+      cursorEnable[cursorColumnLast] = false;
     }
 
     // cursorRow[cursorColumn] = cursorRowMain;
@@ -272,7 +271,7 @@ void setCursor(void) {
 
   for (j = 0; j != NUM_COLS; j++) {
     if (!shiftSelect && cursorColumn != j) {
-      cursorEnable[j] = 0;
+      cursorEnable[j] = false;
     }
     if (cursorEnable[j]) {
       if (cursorRow[j] > 0xF0U)
@@ -307,18 +306,18 @@ void setPlayMarker(void) {
 
 void clearParameterLocks(void) {
   for (j = 0; j != 24; j++)
-    parameterLock[j] = 0;
+    parameterLock[j] = false;
 }
 
 void setDataValue(void) {
-  bool increasing = 0;
+  bool increasing = false;
   uint8_t delta = 1;
-  systemIdle = 0;
+  systemIdle = false;
 
   j = 0;
   if (i & J_UP) {
     j = 1;
-    increasing = 1;
+    increasing = true;
     delta = 16;
   } else if (i & J_DOWN) {
     j = 1;
@@ -326,7 +325,7 @@ void setDataValue(void) {
   } else if (i & J_LEFT) {
     j = 1;
   } else if (i & J_RIGHT) {
-    increasing = 1;
+    increasing = true;
     j = 1;
   }
   if (j) {
@@ -369,7 +368,7 @@ void setDataValue(void) {
           // EMU_printf("setDataValue dataSet[%d]: %d\n", p, dataSet[p]);
         }
         if (p < NUM_PARAMS) {
-          parameterLock[p] = 1;
+          parameterLock[p] = true;
         }
         updateValueSynth(p);
       }
@@ -390,11 +389,10 @@ void getPadMainScreen(void) {
 
   if (joyState & J_B) {
     if (joyState & J_SELECT) {
-      recallMode = 0;
+      snapRecall(RECALL_SAVE);
     } else {
-      recallMode = 1;
+      snapRecall(RECALL_LOAD);
     }
-    snapRecall();
     return;
   }
 
@@ -441,11 +439,11 @@ void printbyte(uint8_t v1, uint8_t v2, uint8_t v3) {
   set_bkg_tiles(1, 16, 10, 1, bkg);
 }
 
-void snapRecall(void) {
+void snapRecall(RecallMode mode) {
   if (cursorRowMain == LAST_ROW) {
     for (l = 0; l < NUM_COLS; l++) {
       if (cursorEnable[l]) {
-        if (!recallMode) {
+        if (mode == RECALL_SAVE) {
           saveDataSet(l);
         } else {
           loadDataSet(l);
@@ -454,7 +452,7 @@ void snapRecall(void) {
       }
     }
   } else {
-    if (!recallMode) {
+    if (mode == RECALL_SAVE) {
       for (j = 0; j != 24; j++)
         dataSetSnap[j] = dataSet[j];
     } else {
diff --git a/Source/screen/main.h b/Source/screen/main.h
index 27751d4..788a2ad 100644
--- a/Source/screen/main.h
+++ b/Source/screen/main.h
@@ -3,7 +3,10 @@
 #include <gbdk/platform.h>
 #include <stdbool.h>
 
-extern bool recallMode;
+typedef enum RecallMode {
+  RECALL_SAVE = 0,
+  RECALL_LOAD = 1,
+} RecallMode;
 
 // v 1.3.3
 extern const uint8_t versionnumber[10];
@@ -54,7 +57,7 @@ void updateDisplay(void);
 void updateDisplaySynth(void);
 void showCursor(void);
 void setPlayMarker(void);
-void snapRecall(void);
+void snapRecall(RecallMode mode);
 void updateSynth(uint8_t synth);
 void showMainScreen(void);
 void renderMainScreen(void);
diff --git a/Source/synth/common.c b/Source/synth/common.c
index 8c17bc4..53eb41d 100644
--- a/Source/synth/common.c
+++ b/Source/synth/common.c
@@ -41,7 +41,7 @@ uint8_t outputSwitchValue[4] = {3, 3, 3, 3};
 void setPitchBendFrequencyOffset(uint8_t synth) {
   uint16_t freqRange;
   uint16_t f = freq[noteStatus[synth].note];
-  systemIdle = 0;
+  systemIdle = false;
   if (pbWheelIn[synth] & PBWHEEL_CENTER) {
     freqRange = freq[pbNoteRange[synth].high];
     currentFreq = (uint16_t)(pbWheelIn[synth] - 0x7F);
diff --git a/Source/synth/noi.c b/Source/synth/noi.c
index 7eb0c85..cc11f2e 100644
--- a/Source/synth/noi.c
+++ b/Source/synth/noi.c
@@ -51,7 +51,7 @@ void playNoteNoi(void) {
   if (valueByte == 0) {
     // Note off
     if (noteStatus[NOI].note == noteIndex) {
-      noteStatus[NOI].active = 0;
+      noteStatus[NOI].active = false;
 
       if (!noiSus) {
         rAUD4ENV = 0x00;
@@ -85,7 +85,7 @@ void playNoteNoi(void) {
 }
 
 void setPitchBendFrequencyOffsetNoise(void) {
-  systemIdle = 0;
+  systemIdle = false;
   if (pbWheelIn[NOI] & PBWHEEL_CENTER) {
     // noteStatus[NOI].note = noteStatus[NOI].note;
     currentFreq = noiFreq[noteStatus[NOI].note +
diff --git a/Source/synth/wav.c b/Source/synth/wav.c
index 6f8d453..92d99d5 100644
--- a/Source/synth/wav.c
+++ b/Source/synth/wav.c
@@ -166,7 +166,7 @@ void playNoteWav(void) {
   pbNoteRange[WAV].high = noteIndex + pbRange[WAV];
 
   noteStatus[WAV].active = true;
-  cueWavSweep = 1;
+  cueWavSweep = true;
   wavNoteOffTrigger = false;
 }
 
@@ -179,7 +179,7 @@ void updateWavSweep(void) {
         wavCurrentFreq = currentFreqData[WAV] - (counterWav << wavSweepSpeed);
         if (!(wavSweepSpeed >> 3U) && (wavCurrentFreq > 0x898U)) {
           wavCurrentFreq = 0U;
-          cueWavSweep = 0U;
+          cueWavSweep = false;
         }
         rAUD3HIGH = wavCurrentFreq >> 8U;
         rAUD3LOW = wavCurrentFreq;
@@ -211,5 +211,5 @@ void loadWav(uint8_t offset) {
   rAUD3LOW = wavCurrentFreq;
   rAUD3HIGH = (wavCurrentFreq >> 8U) | AUDHIGH_RESTART;
 
-  systemIdle = 0;
+  systemIdle = false;
 }