The NES wasn't Nintendo's first electronic device. In the late 1970s, the company became well known for a family of low-cost, simple electronic games called Game & Watch. These were handheld devices about the size of a cassette tape, costing between $10 and $25, which came with a single game to play. Donkey Kong was introduced on such a platform in split-screen format. Games were just simple combinatorial systems displayed on low-cost LCD screens. But Game & Watch machines were sold by the millions and became extremely popular, especially among young audiences who could take them anywhere and share them with friends.
Interest in Game & Watch faded away as the domestic console market exploded. Such a handheld system could not compete with the color and sound found in the titles that appeared both on the NES and the Sega Master System. But in 1989, when everyone had long forgotten about the Game & Watch, Nintendo released a game console that would become its most profitable product ever: the Nintendo Gameboy. It was a handheld, black-and-white console that could play literally hundreds of games by replacing a cartridge, just like a regular home-based console.
The Gameboy was an instant hit, which can partly be explained by the inclusion of the Tetris game with the purchase of the console. The product was targeted at younger audiences, using the same strategy that made Game & Watch so popular in the past. Some Gameboy classics were Pokemon and a special version of Super Mario Bros. Internally, a Gameboy was inspired by the design of the original NES. It used an 8-bit CPU similar to the Intel 8080 or Zilog Z80 and was armed with 8KB of code RAM and an additional 8KB of video RAM. The CPU ran at approximately 4MHz. Screen resolution was 160x144 pixels (20x18 tiles) but, as with the NES, this was a window of an internal memory representation, which was 256x256 pixels (32x32 tiles) across. This allowed fast scrolling by only changing two registers, SCROLLX and SCROLLY, which defined the offset of the said background to the screen. The background was painted with tiles, which were taken from a tile data table. Thus, the screen (called the Background Tile Map) consisted of only 32 rows of 32 bytes each for a total selection of 256 tiles. Each position held the identifier of the tile to be drawn there.
The Gameboy supported one overlay level, so a menu or scoreboard could easily be drawn on top of the scrolling background. This was achieved with a window that was not scrollable but painted at a fixed onscreen position. Window contents were taken from the tile data table as well, so you could position the window onscreen easily with two registers, WNDPOSX and WNDPOSY.
As with the NES, a Gameboy could paint keyed sprites on top of the background for characters, enemies, and so on. It could use both 8x8 and 8x16 sprites, and up to 40 were available. As with the NES, only 10 sprites could be displayed per scanline due to a hardware limitation. Sprite patterns were taken from the sprite pattern table and layered on the screen according to some very unintuitive priority rules: Sprites closer to the left end of the screen would have priority, and thus be laid on top of others; if two sprites happened to share the same X coordinate, the one located in lower positions in the sprite table would have priority.
A Gameboy was a pretty powerful piece of hardware by 1989's standards. It was a mini-version of an NES in black and white, which made it cheaper to manufacture. But what set the Gameboy apart from the competition was its lengthy battery life and the vast array of quality games available for the platform. After all, creating titles for the Gameboy was a very profitable business. It was orders of magnitude cheaper than coding for home-based game consoles (especially since the PlayStation and N64 hit the market). But, on the other hand, the price of the games was not that different. In other words, there was a great margin both for the console manufacturer and the software developer.
Among all gaming platforms, the Gameboy has definitely been the console with the longest life cycle (11 years), and some games are still being sold today. The release of the Gameboy Color in 1998, along with new iterations of classic Nintendo titles, breathed new life into the product, making it break all established records. But even great products like the Gameboy grow old, and thus by the year 2000, Nintendo had already decided to release a newer, more powerful machine. The Gameboy Advance (GBA) was designed with the mission of becoming the substitute for the original Gameboy. The GBA specs are living proof of this philosophy. Powered by a 32-bit ARM CPU working at 16.7MHz, the GBA comes with 32KB of RAM, 96KB of VRAM for graphics, and 16KB of sound RAM. The RAM is built directly into the CPU for faster access. This memory can be further expanded with up to 256KB of RAM external to the CPU.
Graphically speaking, the console uses a 244x160 resolution, which is close to half of the resolution of a SuperNES and not very different from the resolution of an Apple ][. It can perform tile-based backgrounds, including 4096 maximum sprites (256 of which can be layered on a single scanline). This huge number of sprites is especially useful for special effects such as particle systems, because the GBA supports (to an extent) alpha blending. Sprites can also be hardware scaled and rotated. Color depth is 32,768 colors and is selected from a palette of 16M.
In addition, cartridges can hold as much as 64MB of data, putting this console light years ahead of the initial Gameboy design. The result of this design is that many old-school classics such as Mario and The Legend of Zelda can easily be ported to the GBA, ensuring Nintendo a great lineup of games people already love to play. In the end, GBA's horsepower is not that different from a reduced-size SuperNES.