diff --git a/papers/format.md b/papers/format.md
index 97e22a4e..26395502 100644
--- a/papers/format.md
+++ b/papers/format.md
@@ -32,6 +32,8 @@ these fields are 0 in format versions prior to 100 (0.6pre1).
 
 the format versions are:
 
+- 105: Furance dev105
+- 104: Furnace dev104
 - 103: Furnace dev103
 - 102: Furnace 0.6pre1 (dev102)
 - 101: Furnace 0.6pre1 (dev101)
@@ -813,6 +815,37 @@ size | description
  --- | **Sound Unit data** (>=104)
   1  | use sample
   1  | switch roles of phase reset timer and frequency
+ --- | **Game Boy envelope sequence** (>=105)
+  1  | length
+ ??? | hardware sequence data
+     | size is length*3:
+     | 1 byte: command
+     | - 0: set envelope
+     | - 1: set sweep
+     | - 2: wait
+     | - 3: wait for release
+     | - 4: loop
+     | - 5: loop until release
+     | 2 bytes: data
+     | - for set envelope:
+     |   - 1 byte: parameter
+     |     - bit 4-7: volume
+     |     - bit 3: direction
+     |     - bit 0-2: length
+     |   - 1 byte: sound length
+     | - for set sweep:
+     |   - 1 byte: parameter
+     |     - bit 4-6: length
+     |     - bit 3: direction
+     |     - bit 0-2: shift
+     |   - 1 byte: nothing
+     | - for wait:
+     |   - 1 byte: length (in ticks)
+     |   - 1 byte: nothing
+     | - for wait for release:
+     |   - 2 bytes: nothing
+     | - for loop/loop until release:
+     |   - 2 bytes: position
 ```
 
 # wavetable
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 256b0c96..f5422423 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -45,8 +45,8 @@
 #define BUSY_BEGIN_SOFT softLocked=true; isBusy.lock();
 #define BUSY_END isBusy.unlock(); softLocked=false;
 
-#define DIV_VERSION "dev104"
-#define DIV_ENGINE_VERSION 104
+#define DIV_VERSION "dev105"
+#define DIV_ENGINE_VERSION 105
 
 // for imports
 #define DIV_VERSION_MOD 0xff01
diff --git a/src/engine/instrument.cpp b/src/engine/instrument.cpp
index 4d274e18..37c6a9b2 100644
--- a/src/engine/instrument.cpp
+++ b/src/engine/instrument.cpp
@@ -532,6 +532,13 @@ void DivInstrument::putInsData(SafeWriter* w) {
   w->writeC(su.useSample);
   w->writeC(su.switchRoles);
 
+  // GB hardware sequence
+  w->writeC(gb.hwSeqLen);
+  for (int i=0; gb.hwSeqLen; i++) {
+    w->writeC(gb.hwSeq[i].cmd);
+    w->writeS(gb.hwSeq[i].data);
+  }
+
   blockEndSeek=w->tell();
   w->seek(blockStartSeek,SEEK_SET);
   w->writeI(blockEndSeek-blockStartSeek-4);
@@ -1085,6 +1092,15 @@ DivDataErrors DivInstrument::readInsData(SafeReader& reader, short version) {
     su.switchRoles=reader.readC();
   }
 
+  // GB hardware sequence
+  if (version>=105) {
+    gb.hwSeqLen=reader.readC();
+    for (int i=0; i<gb.hwSeqLen; i++) {
+      gb.hwSeq[i].cmd=reader.readC();
+      gb.hwSeq[i].data=reader.readS();
+    }
+  }
+
   return DIV_DATA_SUCCESS;
 }
 
diff --git a/src/engine/instrument.h b/src/engine/instrument.h
index 1c25988e..33e2856b 100644
--- a/src/engine/instrument.h
+++ b/src/engine/instrument.h
@@ -261,12 +261,19 @@ struct DivInstrumentSTD {
 };
 
 struct DivInstrumentGB {
-  unsigned char envVol, envDir, envLen, soundLen;
+  unsigned char envVol, envDir, envLen, soundLen, hwSeqLen;
+  struct HWSeqCommand {
+    unsigned char cmd;
+    unsigned short data;
+  } hwSeq[256];
   DivInstrumentGB():
     envVol(15),
     envDir(0),
     envLen(2),
-    soundLen(64) {}
+    soundLen(64),
+    hwSeqLen(0) {
+    memset(hwSeq,0,256*sizeof(int));
+  }
 };
 
 struct DivInstrumentC64 {
diff --git a/src/engine/platform/gb.h b/src/engine/platform/gb.h
index b00458c2..d4f6ca53 100644
--- a/src/engine/platform/gb.h
+++ b/src/engine/platform/gb.h
@@ -31,6 +31,7 @@ class DivPlatformGB: public DivDispatch {
     unsigned char duty, sweep;
     bool active, insChanged, freqChanged, sweepChanged, keyOn, keyOff, inPorta;
     signed char vol, outVol, wave;
+    unsigned char envVol, envDir, envLen, soundLen;
     DivMacroInt std;
     void macroInit(DivInstrument* which) {
       std.init(which);
@@ -54,7 +55,11 @@ class DivPlatformGB: public DivDispatch {
       inPorta(false),
       vol(15),
       outVol(15),
-      wave(-1) {}
+      wave(-1),
+      envVol(0),
+      envDir(0),
+      envLen(0),
+      soundLen(0) {}
   };
   Channel chan[4];
   DivDispatchOscBuffer* oscBuf[4];