anchor.diff:    final ptr = Pointer<Uint8>.fromAddress(bitmapMemory.address);
     var rowOffset = 0;
   
  -  for (var y = 0; y < bitmapHeight; ++y) {
  +  for (var y = 0; y < bitmapHeight; y++) {
       var pixelOffset = rowOffset;
   
  -    for (var x = 0; x < bitmapWidth; ++x) {
  +    for (var x = 0; x < bitmapWidth; x++) {
         if ((x >= rectX && y >= rectY) &&
             (x <= (rectX + width) && y <= (rectY + height))) {
           ptr.elementAt(pixelOffset).value = blue;
  
positive.code:       if (direction.x == 1) {
          // right
          snakePoints[i].x += 1;
          if (snakePoints[i].x >= (bitmapWidth / 10)) {
            snakePoints[i].x = 0;
          }
        } else if (direction.x == -1) {
  
negative.code:   // init other variables here
    blocksPerWidth = (width / 10).floor();
    blocksPerHeight = (height / 10).floor();
    data = List.filled(blocksPerHeight, List.filled(blocksPerWidth, 0));
  
    resetGame();
  }
  