diff --git a/src/drivers/libretro/libretro.c b/src/drivers/libretro/libretro.c
index 52d2c93..00280fa 100644
--- a/src/drivers/libretro/libretro.c
+++ b/src/drivers/libretro/libretro.c
@@ -60,6 +60,8 @@ void linearFree(void* mem);
 RETRO_HW_RENDER_INTEFACE_GSKIT_PS2 *ps2 = NULL;
 #endif
 
+extern void FCEU_ZapperSetTolerance(int t);
+
 static retro_video_refresh_t video_cb = NULL;
 static retro_input_poll_t poll_cb = NULL;
 static retro_input_state_t input_cb = NULL;
@@ -1300,6 +1302,16 @@ static void check_variables(bool startup)
       else zappermode = RetroLightgun; /*default setting*/
    }
 
+   var.key = "fceumm_zapper_tolerance";
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+   {
+      FCEU_ZapperSetTolerance(atoi(var.value));
+   }
+
+   var.key = "fceumm_region";
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+
    var.key = "fceumm_show_crosshair";
 
    if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
diff --git a/src/drivers/libretro/libretro_core_options.h b/src/drivers/libretro/libretro_core_options.h
index 35ce4c9..16660f0 100644
--- a/src/drivers/libretro/libretro_core_options.h
+++ b/src/drivers/libretro/libretro_core_options.h
@@ -232,6 +232,48 @@ struct retro_core_option_definition option_defs_common[] = {
       },
       "enabled",
    },
+   {
+      "fceumm_zapper_tolerance",
+      "Zapper Tolerance",
+      "Sets how many pixels from target area is on target.",
+      {
+         { "0",  NULL },
+         { "1",  NULL },
+         { "2",  NULL },
+         { "3",  NULL },
+         { "4",  NULL },
+         { "5",  NULL },
+         { "6",  NULL },
+         { "7",  NULL },
+         { "8",  NULL },
+         { "9",  NULL },
+         { "10", NULL },
+         { "11", NULL },
+         { "12", NULL },
+         { "13", NULL },
+         { "14", NULL },
+         { "15", NULL },
+         { "16", NULL },
+         { "17", NULL },
+         { "18", NULL },
+         { "19", NULL },
+         { "20", NULL },
+         { "21", NULL },
+         { "22", NULL },
+         { "23", NULL },
+         { "24", NULL },
+         { "25", NULL },
+         { "26", NULL },
+         { "27", NULL },
+         { "28", NULL },
+         { "29", NULL },
+         { "30", NULL },
+         { "31", NULL },
+         { "32", NULL },
+         { NULL, NULL },
+      },
+      "6",
+   },
    {
       "fceumm_sndquality",
       "Sound Quality",
diff --git a/src/input/zapper.c b/src/input/zapper.c
index 07c6b4b..7656cd5 100644
--- a/src/input/zapper.c
+++ b/src/input/zapper.c
@@ -23,6 +23,13 @@
 
 #include        "share.h"
 
+#define ROUNDED_TARGET
+#ifdef ROUNDED_TARGET
+#define MAX_TOLERANCE 32
+static uint32 targetExpansion[MAX_TOLERANCE+1];
+#endif
+static int tolerance;
+
 typedef struct {
 	uint32 mzx, mzy, mzb;
 	int zap_readbit;
@@ -49,11 +56,19 @@ static void FP_FASTAPASS(3) ZapperFrapper(int w, uint8 * bg, uint8 * spr, uint32
 
 	if (xe > 256) xe = 256;
 
-	if (scanline >= (zy - 4) && scanline <= (zy + 4)) {
+	if (scanline >= (zy - tolerance) && scanline <= (zy + tolerance)) {
+#ifdef ROUNDED_TARGET
+		int dy = scanline - zy;
+		if (dy < 0)
+			dy = -dy;
+		int spread = targetExpansion[dy];
+#else
+		int spread = tolerance;
+#endif
 		while (xs < xe) {
 			uint8 a1, a2;
 			uint32 sum;
-			if (xs <= (zx + 4) && xs >= (zx - 4)) {
+			if (xs <= (zx + spread) && xs >= (zx - spread)) {
 				a1 = bg[xs];
 				if (spr) {
 					a2 = spr[xs];
@@ -140,6 +155,24 @@ static void FP_FASTAPASS(3) UpdateZapper(int w, void *data, int arg) {
 static INPUTC ZAPC = { ReadZapper, 0, 0, UpdateZapper, ZapperFrapper, DrawZapper };
 static INPUTC ZAPVSC = { ReadZapperVS, 0, StrobeZapperVS, UpdateZapper, ZapperFrapper, DrawZapper };
 
+#ifdef ROUNDED_TARGET
+static uint32 InefficientSqrt(uint32 z) {
+	uint32 i;
+	for (i = 0 ; i * i <= z ; i++) ;
+	return i-1;
+}
+#endif
+
+void FCEU_ZapperSetTolerance(int t) {
+#ifdef ROUNDED_TARGET
+	tolerance = t <= MAX_TOLERANCE ? t : MAX_TOLERANCE;
+	for (uint32 y = 0 ; y <= tolerance ; y++)
+		targetExpansion[y] = InefficientSqrt(tolerance*tolerance-y*y);
+#else
+	tolerance = t;
+#endif
+}
+
 INPUTC *FCEU_InitZapper(int w) {
 	memset(&ZD[w], 0, sizeof(ZAPPER));
 	if (GameInfo->type == GIT_VSUNI)
@@ -148,4 +181,3 @@ INPUTC *FCEU_InitZapper(int w) {
 		return(&ZAPC);
 }
 
-