diff --git a/Makefile.am b/Makefile.am
index 4c8566b..5625cb9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,6 +1,6 @@
 AUTOMAKE_OPTIONS = foreign subdir-objects -Wall
 bin_PROGRAMS = forge
-forge_SOURCES = src/main.c src/args.c src/forge.c src/file.c src/window.c src/shaders.c src/timer.c $(top_srcdir)/include/glad/gl.h
+forge_SOURCES = src/main.c src/args.c src/forge.c src/file.c src/window.c src/shaders.c src/timer.c src/strings.c $(top_srcdir)/include/glad/gl.h
 forge_CFLAGS = -Ofast -march=native -flto -funroll-loops -fprefetch-loop-arrays -fno-exceptions -fopenmp -I$(top_srcdir)/include -DGLFW_INCLUDE_NONE
 forge_LDADD = -lm -lGL -lglfw
-include_HEADERS = src/main.h src/args.h src/config.h src/types.h src/forge.h src/file.h src/constants.h src/window.h src/shaders.h src/logs.h src/timer.h $(top_srcdir)/include/glad/gl.h $(top_srcdir)/include/linmath.h
\ No newline at end of file
+include_HEADERS = src/main.h src/args.h src/config.h src/types.h src/forge.h src/file.h src/constants.h src/window.h src/shaders.h src/logs.h src/timer.h src/strings.h $(top_srcdir)/include/glad/gl.h $(top_srcdir)/include/linmath.h
\ No newline at end of file
diff --git a/Makefile.dev b/Makefile.dev
index 5c92869..7862151 100644
--- a/Makefile.dev
+++ b/Makefile.dev
@@ -1,6 +1,6 @@
 TARGET ?= forge
 INSTALL_DIR ?= $(HOME)/.local/bin
-TEST_ARGS ?=
+TEST_ARGS ?= --hot-reload --frag=./shaders
 SHELL := /bin/bash
 
 .PHONY: build
@@ -18,7 +18,7 @@ build:
 		-o build/$(TARGET)
 
 run: build
-	./build/forge --hot-reload --frag=./shaders
+	./build/$(TARGET) $(TEST_ARGS)
 
 .PHONY: install
 install: build
@@ -26,7 +26,12 @@ install: build
 
 .PHONY: valgrind
 valgrind: build
-	valgrind --leak-check=full -s ./build/$(TARGET) $(TEST_ARGS)
+	valgrind \
+		--leak-check=full \
+		--track-fds=all \
+		--show-realloc-size-zero=no \
+		--undef-value-errors=no \
+		./build/$(TARGET) $(TEST_ARGS)
 
 .PHONY: release
 release: clean
diff --git a/README.md b/README.md
index 48aef30..7f4510a 100644
--- a/README.md
+++ b/README.md
@@ -102,7 +102,7 @@ make -f Makefile.dev release-arch
 - [ ] Multi-stage shaders
   - [x] Test 2 stages with render to texture
   - [x] 2 in 2 fx 1 mix 1 fx layout
-  - [ ] Include fragments with special directive
+  - [x] Include common code
   - [ ] 16 input + 16 fx definition and selection (with param)
   - [x] Feedback texture
   - [ ] Free opengl memory
diff --git a/shaders/frag0.glsl b/shaders/frag0.glsl
new file mode 100644
index 0000000..5f21221
--- /dev/null
+++ b/shaders/frag0.glsl
@@ -0,0 +1,19 @@
+#version 460
+
+// COMMON DEFINITIONS AND FUNCTIONS
+
+uniform float iTime;
+uniform vec2 iResolution;
+
+uniform sampler2D frame0;
+uniform sampler2D frame1;
+uniform sampler2D frame2;
+uniform sampler2D frame3;
+uniform sampler2D frame4;
+uniform sampler2D frame5;
+uniform sampler2D frame6;
+uniform sampler2D frame7;
+
+in vec2 vUV;
+
+// TODO things
\ No newline at end of file
diff --git a/shaders/frag1.glsl b/shaders/frag1.glsl
index 8a7b979..7c2af2a 100644
--- a/shaders/frag1.glsl
+++ b/shaders/frag1.glsl
@@ -1,20 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame0;
-uniform sampler2D frame1;
-
-in vec2 vUV;
-layout(location = 3) out vec3 fragColor;
-
-
 // SRC A
 // ---------
 // IN: 0 / 1
 // OUT: 3
 
+layout(location = 3) out vec3 fragColor;
+
 void main() {
     vec2 uv0 = vUV.st;
     float ratio = iResolution.x / iResolution.y;
diff --git a/shaders/frag2.glsl b/shaders/frag2.glsl
index abfe8f7..1bcefb0 100644
--- a/shaders/frag2.glsl
+++ b/shaders/frag2.glsl
@@ -1,19 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame0;
-uniform sampler2D frame2;
-
-in vec2 vUV;
-layout(location = 4) out vec3 fragColor;
-
 // SRC B
 // ---------
 // IN: 0 / 2
 // OUT: 4
 
+layout(location = 4) out vec3 fragColor;
+
 void main() {
     fragColor = vec3(vUV, 0.0) * step(0.3, vUV.x) * step(-0.4, -vUV.x);
 }
\ No newline at end of file
diff --git a/shaders/frag3.glsl b/shaders/frag3.glsl
index 1234a95..bdaee33 100644
--- a/shaders/frag3.glsl
+++ b/shaders/frag3.glsl
@@ -1,19 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame3;
-uniform sampler2D frame5;
-
-in vec2 vUV;
-layout(location = 5) out vec3 fragColor;
-
 // FX A
 // ---------
 // IN: 3 / 5
 // OUT: 5
 
+layout(location = 5) out vec3 fragColor;
+
 void main() {
     fragColor = texture(frame3, vUV).xyz;
 }
\ No newline at end of file
diff --git a/shaders/frag4.glsl b/shaders/frag4.glsl
index a92774c..8d31466 100644
--- a/shaders/frag4.glsl
+++ b/shaders/frag4.glsl
@@ -1,19 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame4;
-uniform sampler2D frame6;
-
-in vec2 vUV;
-layout(location = 6) out vec3 fragColor;
-
 // FX B
 // ---------
 // IN: 4 / 6
 // OUT: 6
 
+layout(location = 6) out vec3 fragColor;
+
 void main() {
     fragColor = texture(frame4, vUV).xyz;
 }
\ No newline at end of file
diff --git a/shaders/frag5.glsl b/shaders/frag5.glsl
index 4a37d53..11270e1 100644
--- a/shaders/frag5.glsl
+++ b/shaders/frag5.glsl
@@ -1,19 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame5;
-uniform sampler2D frame6;
-
-in vec2 vUV;
-layout(location = 7) out vec3 fragColor;
-
 // A+B
 // ---------
 // IN: 5 / 6
 // OUT: 7
 
+layout(location = 7) out vec3 fragColor;
+
 void main() {
     fragColor = texture(frame5, vUV).xyz + texture(frame6, vUV).xyz;
 }
\ No newline at end of file
diff --git a/shaders/frag6.glsl b/shaders/frag6.glsl
index 7f89091..f2a039d 100644
--- a/shaders/frag6.glsl
+++ b/shaders/frag6.glsl
@@ -1,19 +1,12 @@
 #version 460
 
-uniform float iTime;
-uniform vec2 iResolution;
-
-uniform sampler2D frame7;
-uniform sampler2D frame0;
-
-in vec2 vUV;
-layout(location = 0) out vec3 fragColor;
-
 // MFX
 // ---------
 // IN: 7 / 0
 // OUT: 0
 
+layout(location = 0) out vec3 fragColor;
+
 void main() {
     fragColor = texture(frame7, vUV).xyz;
 }
\ No newline at end of file
diff --git a/src/file.c b/src/file.c
index 16b9d06..9cf0542 100644
--- a/src/file.c
+++ b/src/file.c
@@ -5,6 +5,7 @@
 #include <sys/types.h>
 
 #include "logs.h"
+#include "strings.h"
 #include "types.h"
 
 time_t get_file_time(File file) {
@@ -64,4 +65,13 @@ File read_file(char *path) {
   return file;
 }
 
-void free_file(File *file) { free(file->content); }
\ No newline at end of file
+void prepend_file(File *src, File extra) {
+  char *old_src_content = src->content;
+  src->content = concat(extra.content, src->content);
+  free(old_src_content);
+}
+
+void free_file(File *file) {
+  free(file->content);
+  free(file->path);
+}
\ No newline at end of file
diff --git a/src/file.h b/src/file.h
index 3f43eae..be5170b 100644
--- a/src/file.h
+++ b/src/file.h
@@ -11,4 +11,6 @@ void update_file(File *file);
 
 void free_file(File *file);
 
+void prepend_file(File *src, File extra);
+
 #endif
\ No newline at end of file
diff --git a/src/forge.c b/src/forge.c
index 2aae68f..fa704e3 100644
--- a/src/forge.c
+++ b/src/forge.c
@@ -36,21 +36,33 @@ void compute_fps(Window *window, Timer *timer) {
   }
 }
 
-void loop(Window *window, ShaderProgram program, bool hot_reload,
-          File *fragment_shaders, Timer *timer) {
-  Context context;
+void hot_reload(ShaderProgram program, File *common_shader_code,
+                File *fragment_shaders) {
   int i;
+  bool force_update = false;
+
+  if (should_update_file(*common_shader_code)) {
+    update_file(common_shader_code);
+    force_update = true;
+  }
+
+  for (i = 0; i < FRAG_COUNT; i++) {
+    if (force_update || should_update_file(fragment_shaders[i])) {
+      update_file(&fragment_shaders[i]);
+      prepend_file(&fragment_shaders[i], *common_shader_code);
+      update_program(program, fragment_shaders, i);
+    }
+  }
+}
+
+void loop(Window *window, ShaderProgram program, bool hr,
+          File *common_shader_code, File *fragment_shaders, Timer *timer) {
+  Context context;
 
   compute_fps(window, timer);
 
-  if (hot_reload) {
-    // TODO extract to function
-    for (i = 0; i < FRAG_COUNT; i++) {
-      if (should_update_file(fragment_shaders[i])) {
-        update_file(&fragment_shaders[i]);
-        update_program(program, fragment_shaders, i);
-      }
-    }
+  if (hr) {
+    hot_reload(program, common_shader_code, fragment_shaders);
   }
 
   context = get_window_context(window);
@@ -60,23 +72,53 @@ void loop(Window *window, ShaderProgram program, bool hot_reload,
   refresh_window(window);
 }
 
+File read_fragment_shader_file(char *frag_path, int i) {
+  File fragment_shader;
+  char *file_path = malloc(sizeof(char) * 1024);
+
+  sprintf(file_path, "%s/frag%d.glsl", frag_path, i);
+  fragment_shader = read_file(file_path);
+  if (fragment_shader.error) {
+    exit(EXIT_FAILURE);
+  }
+
+  return fragment_shader;
+}
+
+void init_files(char *frag_path, File *common_shader_code,
+                File *fragment_shaders) {
+  int i;
+
+  for (i = 0; i < FRAG_COUNT + 1; i++) {
+    if (i == 0) {
+      (*common_shader_code) = read_fragment_shader_file(frag_path, i);
+    } else {
+      fragment_shaders[i - 1] = read_fragment_shader_file(frag_path, i);
+
+      prepend_file(&fragment_shaders[i - 1], *common_shader_code);
+    }
+  }
+}
+
+void free_files(File *common_shader_code, File *fragment_shaders) {
+  int i;
+
+  for (i = 0; i < FRAG_COUNT; i++) {
+    free_file(&fragment_shaders[i]);
+  }
+
+  free_file(common_shader_code);
+}
+
 void forge_run(Parameters params) {
   File fragment_shaders[FRAG_COUNT];
+  File common_shader_code;
   ShaderProgram program;
   Window *window;
   Timer timer;
   Context context;
-  int i;
-  char file_path[FRAG_COUNT][1024];
 
-  // TODO extract to function
-  for (i = 0; i < FRAG_COUNT; i++) {
-    sprintf(file_path[i], "%s/frag%d.glsl", params.frag_path, i + 1);
-    fragment_shaders[i] = read_file(file_path[i]);
-    if (fragment_shaders[i].error) {
-      exit(EXIT_FAILURE);
-    }
-  }
+  init_files(params.frag_path, &common_shader_code, fragment_shaders);
 
   window = init_window(PACKAGE " " VERSION, params.screen, error_callback,
                        key_callback);
@@ -93,13 +135,11 @@ void forge_run(Parameters params) {
   timer = create_timer(60);
 
   while (!window_should_close(window)) {
-    loop(window, program, params.hot_reload, fragment_shaders, &timer);
+    loop(window, program, params.hot_reload, &common_shader_code,
+         fragment_shaders, &timer);
   }
 
   close_window(window, true);
 
-  // TODO extract to function
-  for (i = 0; i < FRAG_COUNT; i++) {
-    free_file(&fragment_shaders[i]);
-  }
+  free_files(&common_shader_code, fragment_shaders);
 }
\ No newline at end of file
diff --git a/src/shaders.c b/src/shaders.c
index 447bb60..159c414 100644
--- a/src/shaders.c
+++ b/src/shaders.c
@@ -256,6 +256,4 @@ void apply_program(ShaderProgram program, Context context) {
     // draw output
     glDrawArrays(GL_TRIANGLES, 0, 6);
   }
-}
-
-// TODO clean buffers from opengl memories
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/src/strings.c b/src/strings.c
new file mode 100644
index 0000000..6f7dd49
--- /dev/null
+++ b/src/strings.c
@@ -0,0 +1,11 @@
+#include <stdlib.h>
+#include <string.h>
+
+char *concat(const char *s1, const char *s2) {
+  char *result =
+      malloc(strlen(s1) + strlen(s2) + 1); // +1 for the null-terminator
+  // in real code you would check for errors in malloc here
+  strcpy(result, s1);
+  strcat(result, s2);
+  return result;
+}
\ No newline at end of file
diff --git a/src/strings.h b/src/strings.h
new file mode 100644
index 0000000..c7e907a
--- /dev/null
+++ b/src/strings.h
@@ -0,0 +1,6 @@
+#ifndef STRINGS_H
+#define STRINGS_H
+
+char *concat(const char *s1, const char *s2);
+
+#endif
\ No newline at end of file