Vaders v1.1: A space invaders clone
From: Joe Ervin (ervin@pinbot.enet.dec.com)
Newsgroups: comp.sources.hp48
Date: 14 Aug 91 05:25:09 GMT

Hello all,

It is my great pleasure to announce "Vaders" version 1.1, a game for the HP48.  
Vaders is essentially a Space Invaders clone.  This game was written under MPE
v1.1, a multiprogramming environment for the HP48SX.

*****************************************************************************

NEW FEATURES SINCE LAST VERSION:

Since version 1.0, I have mainly fixed bugs to make the game more robust.  The
more significant changes include the following:

* Keyboard I/O is disabled sooner, so pressing the keys while the startup
  screen is being drawn no longer causes problems.

* At startup, the system flags are checked to see whether the clock is being
  displayed on the screen.  If so, the clock flag (-40) is cleared and the
  program exits, similarly to CHIP.  As many of you discovered, the clock 
  display generates interrupts that were interfering with Vaders.

* Vaders now displays in the upper left portion of the display a graphical 
  representation of the number of missle bases you have left.

* The keybuf is now flushed periodically, so you should not have problems with
  keys showing up in the keybuf as many of you reported.

* If you have installed the SCHIP game "Ant", written by Erin Catto, 
  Vaders v1.1 will now scan the Ant library for any installed 
  viruses, and if any exit then Vaders will eradicate them from the system.  
  (Just kidding :-) )

Lastly, let me give a sincere "Thank-You" to all who have reported back to me
on Vaders with either bug reports, suggestions, or just friendly notes of
appreciation, and as usual,  I share the credit for Vaders with Jan Brittenson
for his superb work on Star and MLDL, and with all the other ML "giants" on
who's work Vaders is built.


Now.....on to the game. 

*****************************************************************************

Vaders is a directory on your HP48, in which you will find "VADERS" which is
the game, along with "ABOUT", which serves the usual function.  Press "VADERS"
to run Vaders.  Simple.

You are provided with the familiar missle base at the bottom of the screen,
while "inter-galactic meanies" drop bombs on you from above and move down
toward the surface of the planet.  Your mission is to kill all of the "meanies"
before they get too low.  After you kill all the meanies, the game progresses
to the next wave, where things generally get more difficult.

The controls are as follows:


[blue] = Move missle base left.
   [1] = Move missle base right.
 [spc] = Fire a missle at the meanies.
  [<=] = Quit the game.


If a bomb dropped by a meanie hits the missle base, the missle base explodes
and you continue playing with the next available missle base.  You are allowed
five missle bases, and after the fifth missle base is destroyed the game ends
(although Vaders waits for the quit button before returning to RPL
environment).


The objective is to kill meanies as fast as possible to prevent them from
reaching the surface.  If you allow the meanies to overwhelm you and reach
the bottom of the screen, your missle base explodes spontaneously and the game
ends, so blast away to save the earth!  


Please enjoy this game, and report any bugs, ideas for improvment or notes of
appreciation to me, Joe Ervin, at "ervin@pinbot.enet.dec.com".


Happy Blasting!


>>>Joe Ervin   (whose best score is 29,100 so far...)