The outer shell is made of really thick cardboard and secured with small wooden rods and glue. The buttons are regular buttons expect the joystick, which is 4 micro switch secured together in a tricky way, I'll write about this later ( thanks dad!)
The buttons are connected to the ribbon cable (which comes from the screen) with the help of a small terminal connector. (see the pic). I soldered the terminal connector to the end of the ribbon cable, and this is where I attached the cables of the buttons. It's possible to make it this way because the input depends on which wires from the ribbon cable are connected together. For example if 1 and 2 are connected and the button is pushed down, it starts the game. The 5th and the 6th cable restarts the whole system.
As I mentioned earlier the joystick is really tricky. I attached a sketch (sorry, it's made in Paint) how it's assembled. it's actually just 4 switches and a flat piece of Lego (without edges) secured together with clips. (it's great because I didn't needed analog conversion for the D-pad). The rod of the joystick is glued into the hole of the Lego. I secured the 4 switches on a soldering board. I trimmed down the edges of a flat Lego piece and put it on top of the 4 switches. Then I took 2 gem clips (not the colored ones) and made an x like in the sketch. I secured together the whole joystIck with it, even made a small cut at the side of the lego piece just to make it more secure.
The batteries are held on a small "shelf" . I used the original battery holder of the game trimmed down to size.
it even has a LED light on top, and it looks really cool in the dark.
I replaced the speaker, too.
The decoration is cut out from the original packaging of the game.
UPDATE: I attached a video of it, check it out!
(sorry for my English, and if you liked it, vote for me at the Game.Life 3 contest!)