diff --git a/Makefile.am b/Makefile.am
index ed0c658..c511bc6 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 src/string.c src/config_file.c $(top_srcdir)/include/glad/gl.h $(top_srcdir)/hashmap.c/hashmap.c
+forge_SOURCES = src/main.c src/args.c src/forge.c src/file.c src/window.c src/shaders.c src/timer.c src/string.c src/config_file.c src/rand.c $(top_srcdir)/include/glad/gl.h $(top_srcdir)/hashmap.c/hashmap.c
 forge_CFLAGS = -Ofast -march=native -flto -funroll-loops -fprefetch-loop-arrays -fno-exceptions -fopenmp -I$(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 src/string.h src/config_file.h $(top_srcdir)/include/glad/gl.h $(top_srcdir)/include/linmath.h $(top_srcdir)/include/hashmap.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/string.h src/config_file.h src/rand.h $(top_srcdir)/include/glad/gl.h $(top_srcdir)/include/linmath.h $(top_srcdir)/include/hashmap.h
\ No newline at end of file
diff --git a/Makefile.dev b/Makefile.dev
index 3bba818..59d5fe4 100644
--- a/Makefile.dev
+++ b/Makefile.dev
@@ -1,6 +1,6 @@
 TARGET ?= forge
 INSTALL_DIR ?= $(HOME)/.local/bin
-TEST_ARGS ?= --hot-reload --frag=./shaders --frag-config=./config/shaders.cfg
+TEST_ARGS ?= --hot-reload --frag=./shaders --frag-config=./config/shaders.cfg --demo
 SHELL := /bin/bash
 
 .PHONY: build
diff --git a/README.md b/README.md
index 8ad6061..4cb2210 100644
--- a/README.md
+++ b/README.md
@@ -112,6 +112,9 @@ make -f Makefile.dev release-arch
     - [x] uniform config
     - [x] fragment config
     - [x] subroutines config
+  - [x] demo mode
+  - [ ] random seed injected into shaders
+  - [ ] internal texture size for speed
   - [ ] Clean code and fix things
 - [ ] Midi
   - [ ] Read Midi events
diff --git a/shaders/frag0.glsl b/shaders/frag0.glsl
index 0f0e947..e75ef95 100644
--- a/shaders/frag0.glsl
+++ b/shaders/frag0.glsl
@@ -129,7 +129,7 @@ float divider(float k, int m)
 
 float modTime(float k, int m, float k2)
 {
-    return k * (m * 2  - 1) < 1 ? 0 : mod(divider(k, m) * iTime * iTempo * k2 / 120, 1);
+    return k * (m * 2  - 1) < 1 ? 0 : mod(divider(k, m) * iTime * iTempo * k2 / 240, 1);
 }
 
 float modTime(float k, int m)
@@ -1166,13 +1166,13 @@ subroutine(src_stage_sub) vec4 src_10(vec2 vUV, const float seed)
 
     // logic
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // SRC 11 : video in 2 + thru
 subroutine(src_stage_sub) vec4 src_11(vec2 vUV, const float seed)
 {
-    return src_thru(vUV, tex2, 938);
+    return src_thru(vUV, tex2, seed);
 }
 
 // TODO SRC 12
@@ -1188,7 +1188,7 @@ subroutine(src_stage_sub) vec4 src_12(vec2 vUV, const float seed)
 
     // logic
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // TODO SRC 13
@@ -1204,7 +1204,7 @@ subroutine(src_stage_sub) vec4 src_13(vec2 vUV, const float seed)
 
     // logic
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // TODO SRC 14
@@ -1220,7 +1220,7 @@ subroutine(src_stage_sub) vec4 src_14(vec2 vUV, const float seed)
 
     // logic
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // TODO SRC 15
@@ -1236,7 +1236,7 @@ subroutine(src_stage_sub) vec4 src_15(vec2 vUV, const float seed)
 
     // logic
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // SRC 16 : debug
@@ -1254,7 +1254,7 @@ subroutine(src_stage_sub) vec4 src_16(vec2 vUV, const float seed)
 
     // TODO tmp
     
-    return vec4(0.0);
+    return texture(tex0, vUV);
 }
 
 // 6. effects
@@ -1746,4 +1746,76 @@ subroutine(mix_stage_sub) vec4 mix_2(vec2 vUV, sampler2D ta, sampler2D tb, const
     float k = mean(color_a);
 
     return mix(color_b, color_a, step(mix_src, k));
+}
+
+// alternate mix 1 / 2 for random selection
+
+subroutine(mix_stage_sub) vec4 mix_3(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_4(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_5(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_6(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_7(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_8(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_9(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_10(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_11(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_12(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_13(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_14(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_15(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_1(vUV, ta, tb, seed);
+}
+
+subroutine(mix_stage_sub) vec4 mix_16(vec2 vUV, sampler2D ta, sampler2D tb, const float seed)
+{
+    return mix_2(vUV, ta, tb, seed);
 }
\ No newline at end of file
diff --git a/src/args.c b/src/args.c
index 491f552..29b9499 100644
--- a/src/args.c
+++ b/src/args.c
@@ -30,7 +30,7 @@ static void print_help(int status_code) {
        "  -s, --screen        output screen number (default: primary)\n"
        "  -f, --frag          fragment shaders directory (default: TODO)\n"
        "  -fc, --frag-config  fragment shaders config file (default: TODO)\n"
-       "  -t, --tempo         base tempo (default: 120)\n"
+       "  -t, --tempo         base tempo (default: 60)\n"
        "  --demo              demonstration mode\n");
   exit(status_code);
 }
@@ -84,7 +84,7 @@ Parameters args_parse(int argc, char **argv) {
   params.frag_path = 0;
   params.frag_config_path = 0;
   params.hot_reload = false;
-  params.base_tempo = 120.0f;
+  params.base_tempo = 60.0f;
   params.demo = false;
 
   for (i = 1; i < argc; i++) {
diff --git a/src/forge.c b/src/forge.c
index 04bc07a..de67b1b 100644
--- a/src/forge.c
+++ b/src/forge.c
@@ -8,6 +8,7 @@
 #include "file.h"
 #include "forge.h"
 #include "logs.h"
+#include "rand.h"
 #include "shaders.h"
 #include "timer.h"
 #include "types.h"
@@ -44,19 +45,20 @@ static unsigned int compute_fps(Window *window, Timer *timer) {
 static void init_context(ShaderProgram program, Context *context,
                          Parameters params) {
   int size;
+  int i;
+
   context->tempo = params.base_tempo;
   context->demo = params.demo;
 
-  // TODO temporary state
-  size = program.frag_count * program.sub_type_count * sizeof(unsigned int);
-  context->sub_state = malloc(size);
-  memset(context->sub_state, 0, size);
-  context->sub_state[program.sub_type_count * 0 + 0] = 1;
-  context->sub_state[program.sub_type_count * 1 + 0] = 1;
-  context->sub_state[program.sub_type_count * 2 + 1] = 1;
-  context->sub_state[program.sub_type_count * 3 + 1] = 3;
-  context->sub_state[program.sub_type_count * 5 + 1] = 6;
-  // TODO fix here ??
+  size = program.frag_count * program.sub_type_count;
+  context->sub_state = malloc(size * sizeof(unsigned int));
+  memset(context->sub_state, 0, sizeof(&context->sub_state));
+
+  if (params.demo) {
+    for (i = 0; i < size; i++) {
+      context->sub_state[i] = rand_uint(program.sub_variant_count);
+    }
+  }
 }
 
 static void hot_reload(ShaderProgram program, File *common_shader_code,
@@ -162,10 +164,10 @@ void forge_run(Parameters params) {
 
   window_get_context(window, &context);
 
-  init_context(program, &context, params);
-
   program = shaders_init(fragment_shaders, shader_config, context);
 
+  init_context(program, &context, params);
+
   if (program.error) {
     window_close(window, true);
     exit(EXIT_FAILURE);
diff --git a/src/main.c b/src/main.c
index 4758046..8ea8c45 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,11 +1,13 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <time.h>
 
 #include "args.h"
 #include "config.h"
 #include "forge.h"
 #include "main.h"
+#include "rand.h"
 
 int main(int argc, char **argv) {
   Parameters params;
@@ -14,6 +16,8 @@ int main(int argc, char **argv) {
 
   puts(PACKAGE " " VERSION);
 
+  set_seed((unsigned long)time(NULL));
+
   forge_run(params);
 
   return EXIT_SUCCESS;
diff --git a/src/rand.c b/src/rand.c
new file mode 100644
index 0000000..e386c16
--- /dev/null
+++ b/src/rand.c
@@ -0,0 +1,31 @@
+#include "rand.h"
+
+static unsigned long long mcg_state = 0xcafef00dd15ea5e5u; // Must be odd
+static unsigned long long const multiplier = 6364136223846793005u;
+
+// https://en.wikipedia.org/wiki/Permuted_congruential_generator
+static unsigned long rand(void) {
+  unsigned long long x = mcg_state;
+  unsigned count = (unsigned)(x >> 61);
+
+  mcg_state = x * multiplier;
+  x ^= x >> 22;
+  return (unsigned long)(x >> (22 + count));
+}
+
+void set_seed(unsigned long long seed) {
+  mcg_state = 2 * seed + 1;
+  (void)rand();
+}
+
+unsigned char rand_uchar(const unsigned int max) {
+  return max == 0 ? 0 : (unsigned char)(rand() % max);
+}
+
+unsigned short rand_ushort(const unsigned int max) {
+  return max == 0 ? 0 : (unsigned short)(rand() % max);
+}
+
+unsigned int rand_uint(const unsigned int max) {
+  return max == 0 ? 0 : (unsigned int)(rand() % max);
+}
\ No newline at end of file
diff --git a/src/rand.h b/src/rand.h
new file mode 100644
index 0000000..8de4d70
--- /dev/null
+++ b/src/rand.h
@@ -0,0 +1,9 @@
+#ifndef RAND_H
+#define RAND_H
+
+void set_seed(unsigned long long seed);
+unsigned char rand_uchar(unsigned int max);
+unsigned short rand_ushort(unsigned int max);
+unsigned int rand_uint(unsigned int max);
+
+#endif
\ No newline at end of file
diff --git a/src/shaders.c b/src/shaders.c
index 89f2e3c..0e6bebb 100644
--- a/src/shaders.c
+++ b/src/shaders.c
@@ -345,5 +345,5 @@ void shaders_apply(ShaderProgram program, Context context) {
     }
   }
 
-  use_program(program, program.frag_monitor_index, true, context);
+  use_program(program, program.frag_output_index, true, context);
 }