Much of the game is still about nurturing your Pokémon creatures, breeding them to create new types and pitting them in battle against the Pokémon of other trainers. Crystal also retains the day-and-night gameplay and the ability to import trained Pokémon from older versions of the game or trade with friends .
Also, as in Gold and Silver, you can communicate with in-game non-playing characters by giving them your character's phone number. Doing so will open up opportunities for you to receive rare items and important information. You will also find a radio tuner mixed in with your gear; a radio show can put you in touch with special items, too. For players of Pokimon Red, Blue or Yellow there are two new Pokémon types, Dark and Steel, as well as an all-new world to explore.
In summary, then: a great game, and a very worthwhile buy--but only if you're a Pokémon completist or you haven't already upgraded to Pokémon Gold or Silver.