How The Light Pen Works

[Christopher L. Tumber]

Of course I had to pull mine out and check how it works since theoretically
it shouldn't work at all.

And really, it doesn't, at least not like a normal raster base light pen or
gun works but those boys at GCE were clever...

What happens when you play a light pen "game" is that the game puts a cursor
on the screen. You must use the light pen to DRAG this cursor around. If you
just point the pen at a random location on the screen, it does not work.
Instead, you must point to the cursor and drag it.

So what it's doing is it draw the cursor which is really a shape similar to a
bullseye. As you move the pen, you cross the "rings" of the bullseye. This
new position is detected as with any light pen/gun and the center of the
cursor is moved to this new position. Repeat as neccessary.

So, you could do this with a light gun, but again you'd need to drag around a
gun sight which probably isn't a great idea...