isWithinLimit method
check whether user interaction on the panel within the letter positions limit or outside the area
Implementation
bool isWithinLimit(LetterOffset offset) {
return !(offset.getSmallerOffset.dx < 0 ||
offset.getSmallerOffset.dx > letters.length - 1 ||
offset.getSmallerOffset.dy < 0 ||
offset.getSmallerOffset.dy > letters.first.length - 1);
}