Instalation

You'll need the development packages for the following libraries: SDL, SDL_image, SDL_ttf and SDL_net.
Get the cave9 source:

Download the latest cave_src from the homepage, and extract it;
OR grab the source directly from the subversion repository.

Download the latest cave9_data package from the homepage. It contains the font and texture required for the game. Extract it under the cave9 directory. (The game will look for the data dir under ., ~/.cave9, /usr/local/share/cave9 and /usr/share/cave9, in that order.)
To compile, just run 'make'. If this don't work, please report to cave9@googlegroups.com

Playing

Check the startup options with ./cave9 --help

Use the two diagonal thrusts of your ship to keep it from hitting the cave walls.

You can use the left-right arrow, shift or control keys to activate them.

Use up (or down) arrow key in the one-button mode, or to activate both thrusts in the regular two-button mode.

<Space> will pause/unpause the game.

<F> or <Alt-Enter> toggles full-screen mode.

<Esc> or <Q> quits immediately.

Sample installation session

svn checkout http://cave9.googlecode.com/svn/trunk cave9   &&
cd cave9                                                   &&
make                                                       &&
wget http://cave9.googlecode.com/files/cave9_data-3.tgz    &&
tar -xzf cave9_data-3.tgz                                  &&
rm cave9_data-3.tgz                                        &&
./cave9 --highres --antialiasing 4                         &&
./cave9 --help