Avalon

Avalon (2001) is a Japanese-Polish science fiction film. The film is set in a dystopian future, where the population is hooked on an immersive illegal virtual reality video game called Avalon. One player of the game, Ash wants to reach a secret level hidden within Avalon. The film follows her quest to find the level.
There are a lot of scenes with derelict cities in decay, filmed in nice sepia tones.