When we cracked into this GameBoy, the first thing we found was a two-sided circuit board. A circuit board is a fiberglass board with wires imprinted on it that connect various thins in an electrical circuit (just like the circuit you get with a battery wired to a light bulb and a switch). This circuit board ties together all the different devices that make up the GameBoy.

Several round pads on the circuit board are simple switches. Press on the GameBoy's plastic buttons and thumb pad, and they press down on these pads, connecting wires together to complete part of the circuit (just like switching on a light).

The flat black things you see in the circuit are microchips. Microchips are really complicated circuits made from silicon packed into an insulated housing. These "circuits within a circuit" contain millions of transistors, tiny switches that you can turn on an doff with an electrical charge. Using transistors, it is possible for microchips to run programs to add and subtract numbers, make simple decisions and move data around. Together, millions of simple instructions like these can create a game on the LCD screen.

The biggest device connected to the circuit is this liquid crystal display (LCD). The LCD is basically a big grid of liquid crystals -- twisted crystals that untwist when you apply electrical current to them. By applying electricity to some crystals on the grid and not to others, the GameBoy lets light through in patterns that form the moving picture you see.

The second screen fits directly in front of the LCD screen. It lights up to illuminate the LCD, so you can see it without direct sunlight or a lamp.

The rechargeable lithium ion battery provides electricity to the circuit.

There's a miniature speaker for sound. Electrical current moves a tiny piece of plastic back and forth to generate the air pressure waves that make up sound.

Inside the game cartridge we found another microchip, fastened to another circuit board. This ROM (read-only-memory) microchip holds the program the GameBoy needs to play a specific game. When you slide the cartridge into the GameBoy, the row of gold wires on the cartridge circuit board connects to wires on the GameBoy circuit board. The two connected circuits form one big current.

All these things come together in an amazing way:

The microchips on the main circuit board constantly run the programs stored on different cartridge chips. They also look at the position of the various buttons (in other words, they figure out which buttons you're pressing). The biggest chip, the central processing unit (CPU), does the actual "thinking," while the other chips do what the CPU tells them to do. The CPU tells the LCD what to display, so the LCD shows the correct images for the game. The CPU also plays the right sounds on the built-in speaker.

And that's how the game is played!