[el hippo]

It seems as though you need a way to grab things such as acceleration, hit directions, etc from games such as HL2.

The only problem with this is that it is mostly a client side project as sslice said. Since HL2 is a commercial Valve game, you would probably have to look for any 'secret' HID sdk stuff to see if there is any output data from the game. Otherwise you would probably have to hook into the process memory, or replace game binaries, which would be unwise unless you would only be playing in single player non-VAC mode.

The easiest way out of this would be to host a game with a listen server and load a plugin that way. The plugin would then have access to your system (USB, serial, etc) to allow you to feed data to your gamepad. You would also have direct access to player acceleration, attack, etc. This is a little hacky, but it shouldn't be too different from other C++ win32 i/o access projects.

Hippo