The Neo Geo Pocket was one of the many short-lived handhelds that fell to Nintendo's domination of the handheld market and there was a Sonic game for it. Sonic the Hedgehog Pocket Adventure is almost like a remake of Sonic the Hedgehog 2 using Sonic 3 music. It is also the first Sonic game made by Dimps, who would go on to make almost every other portable Sonic game.
The levels all correspond to Sonic 2 levels, but shuffled up a bit. The level design is even much the same in some stages. Here is the level map of Pocket Adventure's Aquatic Reflex Zone and here is a level map of Sonic 2's Aquatic Ruin for comparison. While they are not exactly the same, they are very similar.
This isn't necessarily a bad thing, as Sonic 2 is a very good game and Pocket Adventure, while not as good, is a worthy entry in the series as well. The music is just mixes of Sonic 3 music, which is another good idea because Sonic 3 has some of the best music in the series. Aquatic Relic Zone's music is just Mushroom Hill Zone on the Neo Geo Pocket.
The game is also notable for using the new Sonic style in a 2D game. His sprites look less rotund while moving and all close-ups and title screen artwork looks like the Sonic Adventure Sonic.
There isn't much to say about this game, it's basically a mish-mash of older games. I've already said all I can on Sonic 2's level design and that's what this game basically is. It's worth playing, there are slight differences in the level and it is a lot of fun, but it's more of a mixture of the Genesis games than a new game in its own right.Summary