A young boy living in New Bark Town in Johto is about to set out on his own Pokémon adventure. The local Pokémon expert, professor Elm, asks him to collect a strange egg from Mr. Pokémon, and gives him his very own Pokémon to take with him. On his travels he meets a rough young boy who treats his Pokémon badly, and the remnants of Team Rocket, still trying to take over the world. His goal, however, is to battle the Gym Leaders for their badges and enter the Pokémon League.
The Johto world is home to 100 new Pokémon, new gym leaders, and new Pokémon attacks. What hasn't changed is the way battles are fought. When you walk through tall grass or a cave then you randomly enter Pokémon battles. Battles are fought through a menu system where you can choose one of your four attacks, an item, switch to one of your other Pokémon, or run away. Similarly if a trainer spots you and walks over then you have to fight them, and the Run command is disabled.
As you fight battles your Pokémon gain in levels. This increases their HP and other stats (the Special stat has now been split into Special Attack and Special Defense). At certain levels your Pokémon will learn new attacks, although you have to choose only four for each Pokémon. Your Pokémon may also evolve - this is usually by levelling up, although there are several special ways that Pokémon evolve, usually by trading them.
A new feature added is the ability for your Pokémon to hold items. Each item does different things, such as making certain attack-types stronger, increasing your health when you're low, etc. There are also two new "Types" in the game - Steel and Dark. These new types shift the balance of the original games, leading to new battle strategies being developed. For instance Dark types are immune to Psychic attacks, meaning that the all-powerful Psychic types in the original now have a threat.
You can still trade Pokémon between games using a link cable. Trading Pokémon makes them grow stronger much faster, but they can be unpredictable if you don't have the right badge. If you have one of the original 151 Pokémon with you, with original attacks, then you can even trade with the Red, Blue, Green and Yellow versions of the game using the Time Capsule. Pokémon Battles make a welcome return, and in these there are certain changes to the regular game's battles - you cannot run and you cannot use items (but held items are, in most cases, allowed).
The game has a full colour pallet when played on a Gameboy Color, and you also have access to the infra-red function. You can point the infra-red lights on the GBCs at each other and both games will receive an item.
