Though genres may be seen as being limited by familiar tropes, they are also marked by difference, variation, and change. Science fiction and romance have a recognisable array of conventions that produce audience pleasures. However, they also need to display something original to set them apart from other examples. Evolution is essential to sustain a genre, and San Junipero does this by introducing elements that could be seen as nostalgic (associated with period dramas set in a recent history) and making the romance a same-sex love affair (distinguishing it from other, heteronormative sci-fi love stories like The Time Traveller's Wife)