diff --git a/fw/Core/Hitcon/App/DinoApp.cc b/fw/Core/Hitcon/App/DinoApp.cc
index 0ca672a..ecfccfa 100644
--- a/fw/Core/Hitcon/App/DinoApp.cc
+++ b/fw/Core/Hitcon/App/DinoApp.cc
@@ -8,6 +8,7 @@
 #include <Logic/RandomPool.h>
 #include <Service/Sched/Scheduler.h>
 #include <Util/uint_to_str.h>
+#include <Secret/secret.h>
 
 #include <cmath>
 
@@ -17,6 +18,8 @@ namespace hitcon {
 namespace app {
 namespace dino {
 
+int combo_button_ctr = 0;
+
 DinoApp dino_app;
 
 DinoApp::DinoApp()
@@ -41,6 +44,17 @@ void DinoApp::OnEntry() {
 void DinoApp::OnExit() { scheduler.DisablePeriodic(&_routine_task); }
 
 void DinoApp::OnButton(button_t button) {
+  if (button == COMBO_BUTTON_DINO[combo_button_ctr]) {
+    combo_button_ctr++;
+  } else {
+    combo_button_ctr = (button == COMBO_BUTTON_DINO[0]) ? 1 : 0;
+  }
+  if (combo_button_ctr == COMBO_BUTTON_DINO_LEN) {
+    // surprise
+    combo_button_ctr = (button == COMBO_BUTTON_DINO[0]) ? 1 : 0;
+    _no_big_cactus = true;
+  }
+
   switch (button & BUTTON_VALUE_MASK) {
     case BUTTON_BACK:
       badge_controller.change_app(&main_menu);
@@ -84,27 +98,27 @@ void DinoApp::Routine(void* unused) {
   if (_obstacle_interval > DINO_OBS_LEAST_DISTANCE) {
     if ((_obstacle_interval > DISPLAY_WIDTH * 2) ||
         (g_fast_random_pool.GetRandom() % _generate_obs_rate == 0)) {
-      switch (g_fast_random_pool.GetRandom() % 4) {
+      switch (g_fast_random_pool.GetRandom() % (_no_big_cactus ? 3 : 4)) {
         case 0:  // bird
           writeObsByte(DISPLAY_WIDTH, bird_bitmap[0]);
           writeObsByte(DISPLAY_WIDTH + 1, bird_bitmap[1]);
           writeObsByte(DISPLAY_WIDTH + 2, bird_bitmap[2]);
           _obstacle_interval = -6;
           break;
-        case 1:  // big cactus
-          writeObsByte(DISPLAY_WIDTH, big_cactus_bitmap[0]);
-          writeObsByte(DISPLAY_WIDTH + 1, big_cactus_bitmap[1]);
-          writeObsByte(DISPLAY_WIDTH + 2, big_cactus_bitmap[2]);
-          _obstacle_interval = -5;
-          break;
-        case 2:  // small tall cactus
+        case 1:  // small tall cactus
           writeObsByte(DISPLAY_WIDTH, small_tall_cactus_bitmap[0]);
           _obstacle_interval = -3;
           break;
-        case 3:  // small short cactus
+        case 2:  // small short cactus
           writeObsByte(DISPLAY_WIDTH, small_short_cactus_bitmap[0]);
           _obstacle_interval = -3;
           break;
+        case 3:  // big cactus
+          writeObsByte(DISPLAY_WIDTH, big_cactus_bitmap[0]);
+          writeObsByte(DISPLAY_WIDTH + 1, big_cactus_bitmap[1]);
+          writeObsByte(DISPLAY_WIDTH + 2, big_cactus_bitmap[2]);
+          _obstacle_interval = -5;
+          break;
         default:
           my_assert(false);
       }
diff --git a/fw/Core/Hitcon/App/DinoApp.h b/fw/Core/Hitcon/App/DinoApp.h
index b971a66..2edba30 100644
--- a/fw/Core/Hitcon/App/DinoApp.h
+++ b/fw/Core/Hitcon/App/DinoApp.h
@@ -34,6 +34,7 @@ class DinoApp : public App {
   uint8_t _game_over : 1;
   uint8_t _dino_ani_frame : 1;
   int8_t _dino_jump_vel : 3;
+  bool _no_big_cactus = false;
   enum dino_actions { DINO_RUN, DINO_JUMP, DINO_CRUNCH } _dino_state;
   void Routine(void* unused);
   bool dinoDied();
diff --git a/fw/Core/Hitcon/Secret/secret.h b/fw/Core/Hitcon/Secret/secret.h
index 25ab34d..5d0bf76 100644
--- a/fw/Core/Hitcon/Secret/secret.h
+++ b/fw/Core/Hitcon/Secret/secret.h
@@ -8,7 +8,11 @@ constexpr button_t COMBO_BUTTON[] = {
     BUTTON_UP,    BUTTON_UP,   BUTTON_DOWN,  BUTTON_DOWN,       BUTTON_LEFT,
     BUTTON_RIGHT, BUTTON_LEFT, BUTTON_RIGHT, BUTTON_BRIGHTNESS, BUTTON_MODE,
 };
+constexpr button_t COMBO_BUTTON_DINO[] = {
+    BUTTON_DOWN, BUTTON_DOWN, BUTTON_RIGHT, BUTTON_RIGHT, BUTTON_OK
+};
 constexpr size_t COMBO_BUTTON_LEN = sizeof(COMBO_BUTTON) / sizeof(button_t);
+constexpr size_t COMBO_BUTTON_DINO_LEN = sizeof(COMBO_BUTTON_DINO) / sizeof(button_t);
 extern int combo_button_ctr;
 
 constexpr uint8_t kGameAchievementData[] = {