diff --git a/game-ctrl/game.c b/game-ctrl/game.c
index 756f202..cc3d209 100644
--- a/game-ctrl/game.c
+++ b/game-ctrl/game.c
@@ -69,24 +69,26 @@ void gameExec(void *handle) {
       proceedDelay--;
       if (proceedDelay == 0) {
         rowIndex = 0;
-        state = e_ClearRows;
+        state = e_Down;
       }
       break;
 
-    case e_ClearRows:
-      state = e_Down;
-      break;
-      
     case e_Down:
       if (! stoneMoveDown()) {
         soundCtrl(SOUND_LOCK);
-        state = e_NewStone;
+        stoneLock();
+        state = e_ClearRows;
       } else {
         proceedDelay = delayFactor(level);
         state = e_DownDelay;
       }
       break;
 
+    case e_ClearRows:
+      // clear filled lines
+      state = e_NewStone;
+      break;
+
 // --- phase: game over ---------------------------------------------------
     case e_GameOver:
       soundCtrl(SOUND_GAMEOVER);
diff --git a/game-ctrl/shapes.c b/game-ctrl/shapes.c
index a9ffb7a..9be8844 100644
--- a/game-ctrl/shapes.c
+++ b/game-ctrl/shapes.c
@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <stddef.h>
 #include <stdlib.h>
+#include <stdbool.h>
 
 #include "shapes.h"
 #include "myrand.h"
@@ -19,6 +20,7 @@ typedef struct {
   orientation_t orientation;
   uint8_t x; // column
   uint8_t y; // row
+  bool locked;
 } stone_t;
 
 typedef struct {
@@ -363,6 +365,11 @@ void stoneCreate() {
   stone.orientation = e_0;
   stone.x = 4;
   stone.y = 0;
+  stone.locked = false;
+}
+
+void stoneLock() {
+  stone.locked = true;
 }
 
 uint8_t stoneIsValid() {
@@ -376,6 +383,12 @@ static uint8_t move(direction_t direction) {
   if (motions[stone.shape].nullRotation && (direction == e_RotateLeft || direction == e_RotateRight)) {
     return 1;
   }
+
+  // if the stone is already locked, do nothing
+  if (stone.locked) {
+    return 0;
+  }
+
   // check whether the pixels to move to are free
   if (canvasIsPixelFree(stone.x + motions[stone.shape].motion[direction][stone.orientation].set[0].x, 
                         stone.y + motions[stone.shape].motion[direction][stone.orientation].set[0].y) &&
diff --git a/game-ctrl/shapes.h b/game-ctrl/shapes.h
index 0950917..a34e1cb 100644
--- a/game-ctrl/shapes.h
+++ b/game-ctrl/shapes.h
@@ -5,6 +5,7 @@
 
 void shapesInit();
 void stoneCreate();
+void stoneLock();
 uint8_t stoneIsValid();
 uint8_t stoneDraw();
 uint8_t stoneMoveDown();