diff --git a/demo1.cpp b/demo1.cpp
index 9659c10..11181e9 100644
--- a/demo1.cpp
+++ b/demo1.cpp
@@ -638,11 +638,10 @@ inline void pixelFunc(PixelInfo pixel)
           rgbToIndex(intensity/2,intensity,intensity/3) :
           rgbToIndex(intensity,intensity/2,0);
 
-
   uint8_t *buf = pokitto.display.screenbuffer;
 
   buf += pixel.position.x * SUBSAMPLE;
-  buf += pixel.position.y * pokitto.display.width;
+  buf += pixel.position.y * SCREEN_WIDTH;
 
   for (uint8_t i = 0; i < SUBSAMPLE - 1; ++i)
     *buf++ = c;
@@ -699,8 +698,7 @@ bool runReleased = false;
 
 int main()
 {
-  pokitto.begin();
-  initPalette();
+  initGeneral();
 
   player.setPositionSquare(4,5);
 
@@ -708,10 +706,6 @@ int main()
   sprites[1] = Sprite(sprite1,14,5,1,100);
   sprites[2] = Sprite(sprite2,15,19,1,200);
 
-  pokitto.display.persistence = 1;
-  pokitto.setFrameRate(FPS);
-  pokitto.display.setFont(fontTiny);
-
   uint32_t previousTime = 0;
   uint32_t dt;
 
diff --git a/general.hpp b/general.hpp
index 43d62c0..2aed030 100644
--- a/general.hpp
+++ b/general.hpp
@@ -223,4 +223,17 @@ public:
   Unit mPixelSize;
 };
 
+void initGeneral()
+{
+  pokitto.begin(); 
+  pokitto.setFrameRate(FPS);
+  pokitto.display.setFont(fontTiny);
+  pokitto.display.persistence = 1;
+
+  initPalette(); 
+
+  for (uint8_t i = 0; i < SUBSAMPLED_WIDTH; ++i)
+    zBuffer[i] = 0;  
+}
+
 #endif