public void markOnlyField() {
// We may assume that we are active - otherwise, the function couldn't be called
if (gameData != null) {
Group group = quadMap.getActiveGroup();
if (group.getFields().contains(position)) {
UnmarkField unmarkField = new UnmarkField(group, position);
unmarkField.execute();
} else {
MarkField markField = new MarkField(group, position);
markField.execute();
}
} else {