diff --git a/index.html b/index.html
index bacdc380..73070393 100644
--- a/index.html
+++ b/index.html
@@ -154,6 +154,7 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
                <li><a class="dropdown-item" href="?platform=coleco">ColecoVision</a></li>
                <li><a class="dropdown-item" href="?platform=sms-sg1000-libcv">Sega SG-1000</a></li>
                <li><a class="dropdown-item" href="?platform=sms-sms-libcv">Sega Master System</a></li>
+               <li><a class="dropdown-item" href="?platform=sms-gg-libcv">Sega Game Gear</a></li>
                <li><a class="dropdown-item" href="?platform=atari7800">Atari 7800</a></li>
                <!--
                <li><a class="dropdown-item" href="?platform=vectrex">Vectrex</a></li>
@@ -323,11 +324,17 @@ if (window.location.host.endsWith('8bitworkshop.com')) {
       <span class="control-def"><span class="control-key small">\</span> Select</span>
       <span class="control-def"><span class="control-key small">Enter</span> Start</span>
     </div>
-    <div class="emucontrols-msx emucontrols-coleco emucontrols-sms text-center small control-insns" style="display:none">
+    <div class="emucontrols-msx emucontrols-coleco text-center small control-insns" style="display:none">
       <span class="control-def"><span class="control-key">&#x2190;&#x2191;&#x2193;&#x2192;</span> Joypad</span>
       <span class="control-def"><span class="control-key small">Space</span> Button A</span>
       <span class="control-def"><span class="control-key small">Shift</span> Button B</span>
     </div>
+    <div class="emucontrols-sms text-center small control-insns" style="display:none">
+      <span class="control-def"><span class="control-key">&#x2190;&#x2191;&#x2193;&#x2192;</span> Joypad</span>
+      <span class="control-def"><span class="control-key small">Space</span> Button A</span>
+      <span class="control-def"><span class="control-key small">Shift</span> Button B</span>
+      <span class="control-def"><span class="control-key small">Enter</span> Start</span>
+    </div>
     <div class="emucontrols-vicdual emucontrols-galaxian emucontrols-vector text-center small control-insns" style="display:none">
       <span class="control-def"><span class="control-key">&#x2190;&#x2191;&#x2193;&#x2192;</span> Joystick</span>
       <span class="control-def"><span class="control-key small">Space</span> Button 1</span>
diff --git a/presets/sms-gg-libcv b/presets/sms-gg-libcv
new file mode 120000
index 00000000..3c624673
--- /dev/null
+++ b/presets/sms-gg-libcv
@@ -0,0 +1 @@
+sms-sms-libcv
\ No newline at end of file
diff --git a/presets/sms-sms-libcv/climber.c b/presets/sms-sms-libcv/climber.c
index cfa83cef..ccec9912 100644
--- a/presets/sms-sms-libcv/climber.c
+++ b/presets/sms-sms-libcv/climber.c
@@ -72,21 +72,23 @@ void music_play(byte index) {
 void music_stop() {
 }
 
-/*{pal:222,n:16}*/
-const char PALETTE0[16] = {
-  0x30, 0x38, 0x3E, 0x3F,
-  0x30, 0x38, 0x3E, 0x3F,
-  0x30, 0x38, 0x3E, 0x3F,
-  0x30, 0x38, 0x3E, 0x3F,
+#ifdef __PLATFORM_SMS_GG_LIBCV__
+/*{pal:444,n:32}*/
+const short PALETTE[32] = {
+  0xe00, 0xa60, 0xee3, 0xddd, 0xe00, 0xa60, 0xee3, 0xddd,
+  0xe00, 0xa60, 0xee3, 0xddd, 0xe00, 0xa60, 0xee3, 0xddd,
+  0xe00, 0x111, 0xddd, 0x43e, 0xaaaa, 0xcccc, 0xeeee, 0xffff,
+  0xe00, 0xa60, 0xee3, 0xddd, 0xe00, 0xa60, 0xee3, 0xddd,
 };
-
-/*{pal:222,n:16}*/
-const char PALETTE1[16] = {
-  0x30, 0x00, 0x3F, 0x03,
-  0x30, 0x38, 0x3E, 0x3F,
-  0x30, 0x38, 0x3E, 0x3F,
-  0x30, 0x38, 0x3E, 0x3F,
+#else
+/*{pal:222,n:32}*/
+const char PALETTE[32] = {
+  0x30, 0x38, 0x3E, 0x3F, 0x30, 0x38, 0x3E, 0x3F,
+  0x30, 0x38, 0x3E, 0x3F, 0x30, 0x38, 0x3E, 0x3F,
+  0x30, 0x00, 0x3F, 0x03, 0x30, 0x38, 0x3E, 0x3F,
+  0x30, 0x38, 0x3E, 0x3F, 0x30, 0x38, 0x3E, 0x3F
 };
+#endif
 
 /// METASPRITES
 
@@ -750,7 +752,7 @@ void pal_bright(byte level) {
   byte or = PALBR_OR[level];
   byte and = PALBR_AND[level];
   for (i=0; i<16; i++) {
-    pal[i] = PALETTE0[i] & and | or;
+    pal[i] = PALETTE[i] & and | or;
   }
   cvu_memtocmemcpy(0xc000, pal, 16);
 }
@@ -799,8 +801,7 @@ void play_scene() {
 
 void setup_graphics() {
   cvu_memtovmemcpy(PATTERN, CHR_GENERIC, sizeof(CHR_GENERIC));
-  cvu_memtocmemcpy(0xc000, PALETTE0, 16);
-  cvu_memtocmemcpy(0xc010, PALETTE1, 16);
+  cvu_memtocmemcpy(0xc000, PALETTE, sizeof(PALETTE));
   flip_sprite_patterns(PATTERN+0x80*32, CHR_GENERIC+0xd0*32, 0x30*32);
   cv_set_left_column_blank(true);
 }
diff --git a/presets/sms-sms-libcv/mode4test.c b/presets/sms-sms-libcv/mode4test.c
index 28ec4fa1..1aadc7ad 100644
--- a/presets/sms-sms-libcv/mode4test.c
+++ b/presets/sms-sms-libcv/mode4test.c
@@ -21,17 +21,23 @@ extern uintptr_t font_bitmap_0[];
 #define SPRITE_PATTERNS 0x3800	// 32*32 = 1024 bytes
 #define SPRITES		0x3c00	// 4*32 = 128 bytes
 
-/*{pal:222,n:16}*/
-const char PALETTE0[16] = {
-  0x10, 0x03, 0x0B, 0x0F, 0x13, 0x17, 0x1B, 0x1F,
-  0x22, 0x28, 0x2A, 0x2E, 0x30, 0x37, 0x3B, 0x3F,
-};
-
-/*{pal:222,n:16}*/
-const char PALETTE1[16] = {
+#ifdef __PLATFORM_SMS_GG_LIBCV__
+/*{pal:444,n:32}*/
+const short PALETTE[32] = {
+  0x2221, 0x4441, 0x6661, 0x8888, 0xaaaa, 0xcccc, 0xeeee, 0xffff,
+  0x2222, 0x4444, 0x6666, 0x8888, 0xaaaa, 0xcccc, 0xeeee, 0xffff,
+  0x2222, 0x4444, 0x6666, 0x8888, 0xaaaa, 0xcccc, 0xeeee, 0xffff,
+  0x2222, 0x4444, 0x6666, 0x8888, 0xaaaa, 0xcccc, 0xeeee, 0xffff,
+};
+#else
+/*{pal:222,n:32}*/
+const char PALETTE[32] = {
+  0x10, 0x03, 0x0B, 0x0F, 0x13, 0x17, 0x1B, 0x1F,
+  0x22, 0x28, 0x2A, 0x2E, 0x30, 0x37, 0x3B, 0x3F,
   0x10, 0x03, 0x0B, 0x0F, 0x13, 0x17, 0x1B, 0x1F,
   0x22, 0x28, 0x2A, 0x2E, 0x30, 0x37, 0x3B, 0x3F,
 };
+#endif
 
 /*{w:8,h:8,bpp:1,count:2,brev:1,np:4,pofs:1,sl:4}*/
 const char PATTERNS[64] = {
@@ -79,8 +85,7 @@ void setup_graphics() {
   // copy sprites to pattern table VRAM
   cvu_memtovmemcpy(PATTERN+32, PATTERNS, sizeof(PATTERNS));
   // copy palettes to VRAM
-  cvu_memtocmemcpy(0xc000, PALETTE0, 16);
-  cvu_memtocmemcpy(0xc010, PALETTE1, 16);
+  cvu_memtocmemcpy(0xc000, PALETTE, sizeof(PALETTE));
 }
 
 // image table has two bytes per cell (name + attribute)
diff --git a/src/common/video/tms9918a.ts b/src/common/video/tms9918a.ts
index 9bee12c4..966d7ca7 100644
--- a/src/common/video/tms9918a.ts
+++ b/src/common/video/tms9918a.ts
@@ -1013,3 +1013,30 @@ export class SMSVDP extends TMS9918A {
     }
 };
 
+export class GameGearVDP extends SMSVDP {
+    cram = new Uint8Array(64); // color RAM
+    cram_latch = 0;
+
+    writeData(value: number) {
+        if (this.writeToCRAM) {
+            //console.log(hex(this.addressRegister), hex(value), hex(this.cram_latch));
+            if (this.addressRegister & 1) { // odd address?
+                let rgb4 = this.cram_latch + (value << 8);
+                let rgba = RGBA((rgb4&15)*17, ((rgb4>>4)&15)*17, ((rgb4>>8)&15)*17);
+                let palindex = this.addressRegister & (this.cram.length-1);
+                this.cram[palindex-1] = this.cram_latch;
+                this.cram[palindex] = value;
+                this.cpalette[palindex >> 1] = rgba;
+                this.prefetchByte = value;
+                this.addressRegister &= this.ramMask;
+                this.redrawRequired = true;
+            } else {
+                this.cram_latch = value; // even address
+            }
+            this.addressRegister++;
+        } else {
+            super.writeData(value);
+        }
+        this.latch = false;
+    }
+}
diff --git a/src/machine/sms.ts b/src/machine/sms.ts
index 9b119816..503a80c7 100644
--- a/src/machine/sms.ts
+++ b/src/machine/sms.ts
@@ -1,11 +1,9 @@
 
-import { Z80, Z80State } from "../common/cpu/ZilogZ80";
-import { BasicScanlineMachine } from "../common/devices";
 import { BaseZ80VDPBasedMachine } from "./vdp_z80";
-import { KeyFlags, newAddressDecoder, padBytes, Keys, makeKeycodeMap, newKeyboardHandler } from "../common/emu";
-import { hex, lzgmini, stringToByteArray } from "../common/util";
-import { TssChannelAdapter, MasterAudio, SN76489_Audio } from "../common/audio";
-import { TMS9918A, SMSVDP } from "../common/video/tms9918a";
+import { newAddressDecoder, padBytes, Keys, makeKeycodeMap } from "../common/emu";
+import { hex } from "../common/util";
+import { MasterAudio, SN76489_Audio } from "../common/audio";
+import { SMSVDP, GameGearVDP } from "../common/video/tms9918a";
 
 // http://www.smspower.org/Development/Index
 // http://www.smspower.org/uploads/Development/sg1000.txt
@@ -28,6 +26,7 @@ var SG1000_KEYCODE_MAP = makeKeycodeMap([
   [Keys.P2_A,     1, 0x4],
   [Keys.P2_B,     1, 0x8],
   [Keys.VK_BACK_SLASH,    1, 0x10], // reset
+  [Keys.VK_ENTER,    1, 0x80], // start/pause
 ]);
 
 export class SG1000 extends BaseZ80VDPBasedMachine {
@@ -61,33 +60,41 @@ export class SG1000 extends BaseZ80VDPBasedMachine {
   setMemoryControl(v:number) { }
   setIOPortControl(v:number) { }
 
+  readIO(addr:number) {
+    switch (addr & 0xc1) {
+      case 0x40: return this.getVCounter();
+      case 0x41: return this.getHCounter();
+      case 0x80: return this.vdp.readData();
+      case 0x81: return this.vdp.readStatus();
+      case 0xc0: return this.inputs[0] ^ 0xff;
+      case 0xc1: return this.inputs[1] ^ 0xff;
+    }
+    return 0;
+  }
+
+  writeIO(addr:number, val:number) {
+    switch (addr & 0xc1) {
+      case 0x00: return this.setMemoryControl(val);
+      case 0x01: return this.setIOPortControl(val);
+      case 0x40:
+      case 0x41: return this.psg.setData(val);
+      case 0x80: return this.vdp.writeData(val);
+      case 0x81: return this.vdp.writeAddress(val);
+    }
+  }
+
   newIOBus() {
     return {
       read: (addr:number) => {
         addr &= 0xff;
         //console.log('IO read', hex(addr,4));
-        switch (addr & 0xc1) {
-          case 0x40: return this.getVCounter();
-          case 0x41: return this.getHCounter();
-          case 0x80: return this.vdp.readData();
-          case 0x81: return this.vdp.readStatus();
-          case 0xc0: return this.inputs[0] ^ 0xff;
-          case 0xc1: return this.inputs[1] ^ 0xff;
-        }
-        return 0;
+        return this.readIO(addr);
       },
       write: (addr:number, val:number) => {
         addr &= 0xff;
         val &= 0xff;
         //console.log('IO write', hex(addr,4), hex(val,2));
-        switch (addr & 0xc1) {
-          case 0x00: return this.setMemoryControl(val);
-          case 0x01: return this.setIOPortControl(val);
-          case 0x40:
-          case 0x41: return this.psg.setData(val);
-          case 0x80: return this.vdp.writeData(val);
-          case 0x81: return this.vdp.writeAddress(val);
-        }
+        this.writeIO(addr, val);
       }
     };
   }
@@ -223,3 +230,17 @@ export class SMS extends SG1000 {
   }
 }
 
+// https://segaretro.org/images/1/16/Sega_Game_Gear_Hardware_Reference_Manual.pdf
+export class GameGear extends SMS {
+  newVDP(frameData, cru, flicker) {
+    return new GameGearVDP(frameData, cru, flicker);
+  }
+  readIO(addr:number) {
+    switch (addr & 0xc1) {
+      case 0x00: return (~this.inputs[1] & 0x80) | 0x40;
+      case 0xdc: return this.inputs[0] ^ 0xff;
+      case 0xdd: return this.inputs[1] ^ 0xff;
+    }
+    return super.readIO(addr);
+  }
+}
diff --git a/src/platform/sms.ts b/src/platform/sms.ts
index 5248346c..5dcf5b27 100644
--- a/src/platform/sms.ts
+++ b/src/platform/sms.ts
@@ -1,5 +1,5 @@
 
-import { SG1000, SMS } from "../machine/sms";
+import { GameGear, SG1000, SMS } from "../machine/sms";
 import { Platform, BaseZ80MachinePlatform } from "../common/baseplatform";
 import { PLATFORMS } from "../common/emu";
 
@@ -46,7 +46,17 @@ class SMSPlatform extends BaseZ80MachinePlatform<SMS> implements Platform {
   readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
 }
 
+class GameGearPlatform extends BaseZ80MachinePlatform<GameGear> implements Platform {
+
+  newMachine()          { return new GameGear(); }
+  getPresets()          { return SMS_PRESETS; }
+  getDefaultExtension() { return ".c"; };
+  readAddress(a)        { return this.machine.read(a); }
+  readVRAMAddress(a)    { return this.machine.readVRAMAddress(a); }
+}
+
 ///
 
 PLATFORMS['sms-sg1000-libcv'] = SG1000Platform;
 PLATFORMS['sms-sms-libcv'] = SMSPlatform;
+PLATFORMS['sms-gg-libcv'] = GameGearPlatform;
diff --git a/src/worker/workermain.ts b/src/worker/workermain.ts
index 1639b165..5fcd63b3 100644
--- a/src/worker/workermain.ts
+++ b/src/worker/workermain.ts
@@ -388,6 +388,7 @@ var PLATFORM_PARAMS = {
 };
 
 PLATFORM_PARAMS['sms-sms-libcv'] = PLATFORM_PARAMS['sms-sg1000-libcv'];
+PLATFORM_PARAMS['sms-gg-libcv'] = PLATFORM_PARAMS['sms-sms-libcv'];
 
 var _t1;
 export function starttime() { _t1 = new Date(); }
@@ -1060,6 +1061,8 @@ export function preprocessMCPP(step:BuildStep, filesys:string) {
   if (step.mainfile) {
     args.unshift.apply(args, ["-D", "__MAIN__"]);
   }
+  let platform_def = (platform.toUpperCase() as any).replaceAll(/[^a-zA-Z0-9]/g,'_');
+  args.unshift.apply(args, ["-D", `__PLATFORM_${platform_def}__`]);
   if (params.extra_preproc_args) {
     args.push.apply(args, params.extra_preproc_args);
   }