diff --git a/src/input.c b/src/input.c
index 9e04a80..fc4a176 100644
--- a/src/input.c
+++ b/src/input.c
@@ -198,8 +198,12 @@ void input_set_layer_button_state(input_layer_t layer, button_t button, float st
 }
 
 void input_set_button_state(button_t button, float state) {
-	error_if(button < 0 || button >= INPUT_BUTTON_MAX, "Invalid input button %d", button);
 
+	if (sbs > 0)
+		// do not process buttons twice per frame
+		return;
+
+	error_if(button < 0 || button >= INPUT_BUTTON_MAX, "Invalid input button %d", button);
 	input_set_layer_button_state(INPUT_LAYER_SYSTEM, button, state);
 	input_set_layer_button_state(INPUT_LAYER_USER, button, state);
 
diff --git a/src/render.h b/src/render.h
index 74d96cc..c7affa6 100644
--- a/src/render.h
+++ b/src/render.h
@@ -38,7 +38,7 @@ vec2i_t render_size(void);
 void render_frame_prepare(void);
 void render_frame_end(void);
 
-void render_set_view(vec3_t pos, vec3_t angles);
+void render_set_view(vec3_t pos, vec3_t angles, float lrdist);
 void render_set_view_2d(void);
 void render_set_model_mat(mat4_t *m);
 void render_set_depth_write(bool enabled);
diff --git a/src/render_gl.c b/src/render_gl.c
index f09b49b..0b781e6 100644
--- a/src/render_gl.c
+++ b/src/render_gl.c
@@ -21,7 +21,7 @@
 	#include <GL/gl.h>
 #endif
 
-
+int sbs = 0; // -1:left +1:rigth 0:no-sbs
 
 #include <stb_image_write.h>
 
@@ -437,7 +437,7 @@ void render_init(vec2i_t screen_size) {
 	prg_game = shader_game_init();
 	use_program(prg_game);
 
-	render_set_view(vec3(0, 0, 0), vec3(0, 0, 0));
+	render_set_view(vec3(0, 0, 0), vec3(0, 0, 0), 0/*lrdist*/);
 	render_set_model_mat(&mat4_identity());
 
 	glEnable(GL_CULL_FACE);
@@ -575,15 +575,19 @@ vec2i_t render_size(void) {
 void render_frame_prepare(void) {
 	use_program(prg_game);
 	glBindFramebuffer(GL_FRAMEBUFFER, backbuffer);
-	glViewport(0, 0, backbuffer_size.x, backbuffer_size.y);
+	glViewport(sbs? (sbs + 1) * backbuffer_size.x / 4: 0, 0, backbuffer_size.x / (!!sbs + 1), backbuffer_size.y);
 
 	glBindTexture(GL_TEXTURE_2D, atlas_texture);
 	glUniform2f(prg_game->uniform.screen, 0, 0);
 	glEnable(GL_DEPTH_TEST);
 	glDepthMask(true);
 	glDisable(GL_POLYGON_OFFSET_FILL);
-	glClearColor(0, 0, 0, 1);
-	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+	if (sbs <= 0)
+	{
+		// only when rendering total of left
+		glClearColor(0, 0, 0, 1);
+		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+	}
 	glEnable(GL_DEPTH_TEST); 
 }
 
@@ -599,8 +603,12 @@ void render_frame_end(void) {
 	glUniform1f(prg_post->uniform.time, system_cycle_time());
 	glUniform2f(prg_post->uniform.screen_size, screen_size.x, screen_size.y);
 
-	glClearColor(0, 0, 0, 1);
-	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+	if (sbs <= 0)
+	{
+		// only when rendering total of left
+		glClearColor(0, 0, 0, 1);
+		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+	}
 
 	rgba_t white = rgba(128,128,128,255);
 	tris_buffer[tris_len++] = (tris_t){
@@ -638,13 +646,14 @@ void render_flush(void) {
 }
 
 
-void render_set_view(vec3_t pos, vec3_t angles) {
+void render_set_view(vec3_t pos, vec3_t angles, float lrdist) {
 	render_flush();
 	render_set_depth_write(true);
 	render_set_depth_test(true);
 
 	view_mat = mat4_identity();
-	mat4_set_translation(&view_mat, vec3(0, 0, 0));
+	mat4_set_translation(&view_mat, vec3(-lrdist, 0, 0));
+
 	mat4_set_roll_pitch_yaw(&view_mat, vec3(angles.x, -angles.y + M_PI, angles.z + M_PI));
 	mat4_translate(&view_mat, vec3_inv(pos));
 	mat4_set_yaw_pitch_roll(&sprite_mat, vec3(-angles.x, angles.y - M_PI, 0));
diff --git a/src/system.c b/src/system.c
index 7440ba5..4d3918a 100644
--- a/src/system.c
+++ b/src/system.c
@@ -43,11 +43,23 @@ void system_update(void) {
 		cycle_time -= 3600 * M_PI;
 	}
 	
+	// render total (sbs==0) or left (sbs==-1)
+
 	render_frame_prepare();
 	
 	game_update();
 
 	render_frame_end();
+
+	if (sbs)
+	{
+		sbs = 1; // now render right
+		render_frame_prepare();
+		game_update();
+		render_frame_end();
+		sbs = -1;
+	}
+
 	input_clear();
 	mem_temp_check();
 }
diff --git a/src/utils.h b/src/utils.h
index dcebb31..bb9fe7b 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -4,6 +4,8 @@
 #include <string.h>
 #include "types.h"
 
+extern int sbs; // side by side -1:left 0:no-sbs +1:right
+
 #ifdef WIN32
 	#undef min
 	#undef max
diff --git a/src/wipeout/game.c b/src/wipeout/game.c
index f2c16bc..8bd139c 100755
--- a/src/wipeout/game.c
+++ b/src/wipeout/game.c
@@ -417,6 +417,9 @@ save_t save = {
 		[A_THRUST] = {INPUT_KEY_X, INPUT_GAMEPAD_A},
 		[A_FIRE] = {INPUT_KEY_Z, INPUT_GAMEPAD_X},
 		[A_CHANGE_VIEW] = {INPUT_KEY_A, INPUT_GAMEPAD_Y},
+		[A_TOGGLE_SBS] = {INPUT_KEY_I, INPUT_INVALID},
+		[A_SBS_MORE] = {INPUT_KEY_P, INPUT_INVALID},
+		[A_SBS_LESS] = {INPUT_KEY_O, INPUT_INVALID},
 	},
 	.analog_response = 2, // Exponent for stick turn input
 
diff --git a/src/wipeout/game.h b/src/wipeout/game.h
index 98e789c..2dd46ae 100755
--- a/src/wipeout/game.h
+++ b/src/wipeout/game.h
@@ -29,6 +29,9 @@ typedef enum {
 	A_THRUST,
 	A_FIRE,
 	A_CHANGE_VIEW,
+	A_TOGGLE_SBS,
+	A_SBS_MORE,
+	A_SBS_LESS,
 	NUM_GAME_ACTIONS,
 
 	A_MENU_UP,
diff --git a/src/wipeout/main_menu.c b/src/wipeout/main_menu.c
index 7dd0b3f..b54cb0c 100755
--- a/src/wipeout/main_menu.c
+++ b/src/wipeout/main_menu.c
@@ -37,7 +37,7 @@ static struct {
 } models;
 
 static void draw_model(Object *model, vec2_t offset, vec3_t pos, float rotation) {
-	render_set_view(vec3(0,0,0), vec3(0, -M_PI, -M_PI));
+	render_set_view(vec3(0,0,0), vec3(0, -M_PI, -M_PI), 0/*lrdist*/);
 	render_set_screen_position(offset);
 	mat4_t mat = mat4_identity();
 	mat4_set_translation(&mat, pos);
@@ -263,7 +263,9 @@ static void page_options_controls_init(menu_t *menu) {
 	menu_page_add_button(page, A_THRUST, "THRUST", page_options_controls_set_init);
 	menu_page_add_button(page, A_FIRE, "FIRE", page_options_controls_set_init);
 	menu_page_add_button(page, A_CHANGE_VIEW, "VIEW", page_options_controls_set_init);
-
+	menu_page_add_button(page, A_TOGGLE_SBS, "3D SBS", page_options_controls_set_init);
+	menu_page_add_button(page, A_SBS_MORE, "SBS MORE", page_options_controls_set_init);
+	menu_page_add_button(page, A_SBS_LESS, "SBS LESS", page_options_controls_set_init);
 	menu_page_add_toggle(page, save.analog_response - 1, "ANALOG RESPONSE", analog_response, len(analog_response), toggle_analog_response);
 }
 
diff --git a/src/wipeout/menu.c b/src/wipeout/menu.c
index 4cd005a..818a373 100644
--- a/src/wipeout/menu.c
+++ b/src/wipeout/menu.c
@@ -84,6 +84,8 @@ void menu_update(menu_t *menu) {
 	// Handle menu entry selecting
 	int last_index = page->index;
 	int selected_data = 0;
+  if (sbs <= 0)
+  {
 	if (page->entries_len > 0) {
 		if (flags_is(page->layout_flags, MENU_HORIZONTAL)) {
 			if (input_pressed(A_MENU_LEFT)) {
@@ -114,7 +116,7 @@ void menu_update(menu_t *menu) {
 		}
 		selected_data = page->entries[page->index].data;
 	}
-
+  }
 	if (page->draw_func) {
 		page->draw_func(menu, selected_data);
 	}
@@ -193,6 +195,8 @@ void menu_update(menu_t *menu) {
 		}
 	}
 
+  if (sbs <= 0)
+  {
 	// Handle back buttons
 	if (input_pressed(A_MENU_BACK) || input_pressed(A_MENU_QUIT)) {
 		if (menu->index != 0) {
@@ -201,6 +205,7 @@ void menu_update(menu_t *menu) {
 		}
 		return;
 	}
+  }
 
 	if (page->entries_len == 0) {
 		return;
@@ -210,6 +215,8 @@ void menu_update(menu_t *menu) {
 	// Handle toggle entries
 	menu_entry_t *entry = &page->entries[page->index];
 
+  if (sbs <= 0)
+  {
 	if (entry->type == MENU_ENTRY_TOGGLE) {
 		if (input_pressed(A_MENU_LEFT)) {
 			sfx_play(SFX_MENU_SELECT);
@@ -242,4 +249,5 @@ void menu_update(menu_t *menu) {
 			}
 		}
 	}
+  }
 }
diff --git a/src/wipeout/race.c b/src/wipeout/race.c
index 85ed783..131dafd 100755
--- a/src/wipeout/race.c
+++ b/src/wipeout/race.c
@@ -29,6 +29,7 @@ static bool menu_is_scroll_text = false;
 static bool has_show_credits = false;
 static float attract_start_time;
 static menu_t *active_menu = NULL;
+static float lrdist = 150;
 
 void race_init(void) {
 	ingame_menus_load();
@@ -68,6 +69,8 @@ void race_init(void) {
 }
 
 void race_update(void) {
+  if (sbs <= 0)
+  {
 	if (is_paused) {
 		if (!active_menu) {
 			active_menu = pause_menu_init();
@@ -101,9 +104,22 @@ void race_update(void) {
 		}
 	}
 
+    if (input_pressed(A_TOGGLE_SBS)) {
+        sbs = sbs? 0: -1;
+    }
+    if (input_pressed(A_SBS_MORE)) {
+        lrdist += 10;
+        printf("+sbs = %g\n", lrdist);
+    }
+    if (input_pressed(A_SBS_LESS)) {
+        lrdist -= 10;
+        printf("-sbs = %g\n", lrdist);
+    }
+  }
+
 
 	// Draw 3D
-	render_set_view(g.camera.position, g.camera.angle);
+	render_set_view(g.camera.position, g.camera.angle, lrdist * sbs);
 	render_set_screen_position(g.camera.shake);
 
 	render_set_cull_backface(false);