I was wondering what I could do for the Keyboard Vs Mouse challenge, and I just kind of thought of this. This isn't bagatelle in the strictest sense because the ball is not being hit up the table in order to go down, it is just dropped from the top. This is because I felt that there was not enough room widthways to add a launcher section on the plate. Plus it wouldn't have worked with the shape.

This project only uses parts from a keyboard (apart from the ball, couldn't find one in my keyboard) plus some adhesive material, depending on your preference.

Step 1: Materials

OK, not much needed for this project, just:
A keyboard
A ball to go down the bagatelle - I used the ball from a mouse because it was a convenient size, but it was a bit heavy. (just to be clear, I am on the keyboard side of the contest and only used the mouse because I had one close by)
Hot glue (or any other type of glue you think may work - blutack for a more temporary solution)
Glue gun (if you are using hot glue)
and a screwdriver for opening up the keyboard.

Step 2: Opening the Keyboard

This is pretty simple, just take all of the screws from the back of the keybord and pull the two halves apart. After you have taken the plastic backing off, there will be some more screws in the metal plate - take these out as well because we're going to be using this plate.

Since the Image notes don't seem to be working, it seems that I'll have to put what I want to say below:

The first picture is of the keyboard that we're going to be wreck...uh I mean using. I'm joking (of course). If you only secure the keys with blutack then you will be able to put the keyboard back together afterwards - it might even work :)

The second picture is of the keyboard with the plastic back taken off.

The third picture is of all of the parts you should have. We will need the metal bit at the bottom, the bit with all of the keys on and the plastic backing. With the flexy plasticky bit that has circuits on I suggest you make something like this to use up as many of the parts of the keyboard as you can and be completely ecological.

Step 3: Pop Out the Keys

Pop out all of the keys that you'll need - If you are not sure how many you'll need then pop them out as you need them.

I found it easier to pop out the keys from behind but you can just do whatever you find easiest.

Step 4: Propping Up the Plate

On the back of the spacebar there should be a piece of metal that looks like the bit in the picture below. Take the thinnest end of the keyboard and glue the piece of metal to the back in a way that props it up. If you prefer, you could attach a kind of hinge system so that it collapses and it portable, but I'm not taking mine anywhere and I found that glueing it is easier.

You should end up with something that looks like the second picture below.

Step 5: Attach the Keys

The first thing that you should do while carrying out this step is to put the keys in the configuration that you think will be the most challenging/fun. Then you should glue (or blutack them) down in these places. I put in a semicircle halfway up that is quite hard to get into, so I made it worth 4 points.

Remember to put the number underneath each possible endpoint to signify their value.

Step 6: Add the Sides

Depending on how permanant your bagatelle is, you either want to glue props on, of just prop it up with whatever comes to hand. You should use the plastic back on one side and the part that used to hold the keys on the other.