//generic story image swapping
function setImage(imageControl, newImageFile) {
  imageControl.src = newImageFile;
}

function sprintf() {
  var numArgs = arguments.length;
  var rsltStr = arguments[0];
  for (var i = 1; i < numArgs; i++) {
    var pattern = "\\{" + (i-1) + "\\}";
    var reg = new RegExp(pattern, "g");
    rsltStr = rsltStr.replace(reg, arguments[i]);
  }
  return rsltStr;
}