Yes, there are many great 'crowpaw and feathertail fanfics' out there. You can start by looking on popular fanfic websites like Archive of Our Own. Just search for 'crowpaw and feathertail' and you'll likely find a variety of stories written by different authors, each with their own take on the relationship between these two characters.
The unique relationship between them can make it interesting. Their different personalities, with Crowpaw being more brash and Feathertail being gentle yet strong, can create great character dynamics in a fanfic.
One of the features could be a variety of levels with increasing difficulty. Also, the game might have different enemies and obstacles to overcome, adding to the challenge. The controls might be simple and intuitive for easy gameplay.
It's because it adds depth and intrigue to the story. Different backgrounds and experiences of the old man and his daughter can create all sorts of conflicts and emotions.