xstarcastle is a fork of xsc version 1.5, by Mark B. Hanson.  xstarcastle 
aims to be similar to the arcade version of Star Castle by Cinemastronics.

The program should build on any reasonable UNIX box with a decent C++
compiler and X libraries and SDL libraries installed.  Some portability 
adjustments may be necessary depending on what variety of bogosities exist 
in your C++ development environment.  

You will have to run make install so that program can find the wav files.

Instructions:
=============

- D turns the ship counter-clockwise
- F turns the ship clockwise

- J runs the thruster
- K fires the laser

- P toggles the pause (moving the cursor out of the window pauses the game)
- Q quits the game
- space starts a new game

These keybindings might seem non-standard but they are similar to the
button layout on the Star Castle arcade machines.

The object is to blast a hole in the rings and destroy the enemy ship.
The only problem is that it tracks your every move and as soon as you
knock a hole in all three rings, and they all line up, it lets loose
with the big nasty fireballs.  Avoid them.  Avoid the little blue
buzzers, too.  Shoot 'em if you want, but they get you no points at all.

Destroying all the segments of the outer ring causes a new solid ring
to be generated.  You must hit each ring segment twice to destroy it.

If you kill off the enemy ship, you are given another life.

It all gets more difficult as the levels progress.  If you can kill the 
enemy ship 10 times, you'll be playing on the very hardest level.
