Planetary Defenses:

If you are sitting in the same sector as your planets, no one 
else can land on any of them, unless they destroy you first. So, 
the more fighters and shields you have on you, the better. Note: 
only occupied ships defend planets. One type of ship, the 
Tholian Sentinel, is very special in this function. It's fighters
and shields will defend planets at 4 to 1 odds! It can carry 
4,000 shields, plus 2,500 fighters, which is a relatively small 
investment, but it will take an invader in an ISS about 17,333 
fighters to destroy! This is an excellent way to defend your 
planets at the beginning weeks of the game.

Planets can be upgraded, and each higher level of citadel 
provides a new weapon:

Level 1 Citadel: Provides really no defense. Any invader, or 
casual visitor can land on this planet at will, and simply
take away anything you leave on the planet. They can steal 
your fighters, products, colonists, and any money you leave 
in the citadel! 

Level 2 Citadel: Fighters left on this planet will try to 
prevent anyone else from landing on it. These fighters can be
offensive or defensive or some of each, as controlled by the 
"Military Reaction Level". Defensive fighters resist invaders 
at the best odds and give the invader the option of retreating,
thereby leaving your fighters intact. ALWAYS set Military 
Reaction Level to ZERO! This makes the fighters totally 
defensive and produces the best odds.


Level 3 Citadel: Quasar Cannon. A neat gadget that will 
automatically shoot at invaders entering the sector, or 
trying to land. Shots use up fuel ore from the planet, so be 
sure you have LOTS of it. NEVER sell fuel ore for any reason!
There are 2 type of cannon shots. Shots into the sector will 
use up 3 units of fuel ore for each point of damage to the 
invader. Shots at ships landing on the planet will deal two 
points of damage for each unit of fuel ore expended, which
is 6 times as efficent on fuel usage as a shot into the sector.

It is best to have several cannons together in the sector, so 
they can defend each other. I always have 5 cannons per sector, 
which is the maximum. When an invader enters the sector, the 
cannon on the lowest numbered planet shoots first. If the 
invader survives the shot, then the next higher numbered planet
fires, and so on. If the invader's ship is destroyed, then any 
cannon that has not yet fired, will NOT fire at all, thereby 
saving it's fuel ore. This brings up a strategy point, of how 
large the shots should be. I like to set the sector level for 
the first planet very low, perhaps 5% or so, which will destroy 
small ships, and conserve fuel that way.  The next planet is 
usually set to 15%, and the later ones at 30%. This way, the 
first planet takes care of little ships, and later planets don't 
even fire, thereby saving fuel. When larger ships enter, several
or all of the cannons fire, each with succesively larger shots.
After all, it's pointless to blow away all your fuel ore on a 
tiny little scout ship, when a fully loaded ISS will follow right
behind it, and destroy the now unloaded cannons.

Upon entering the sector, the cannons will fire, then you get a 
prompt for attacking the sector fighters. Cannons will shoot again,
every time you shoot at the sector fighters, so try to nail them 
all in one shot.

Please note that for reasons unknown, an atmosphere shot will be 
exactly half the percentage you set it to.


Level 4 Citadel: This is a planet you can move to another sector.
Doing this permits planet trading and many other useful options.
It takes 400 units of fuel ore for every sector of distance moved.

Level 5 Citadel: Planetary Shields. These shields will prevent 
photon torpedos from disabling your quasar cannons. Planetary
Shields are actually the same as ship shields, and you must buy 
them and dump them in the citadel. An invader must destroy all 
the shields before he can even SEE how many fighters are on the 
planet, which he will have to destroy next! Planetary shields 
defend at 22.5:1 odds divided by the attacking ship's combat 
odds. For example, an ISS needs about 15,000 fighters to destroy 
1,000 planetary shields.


Level 6 Citadel: Planetary Interdictor. This prevents any invader's
ship from ever leaving the sector! Any attempt to leave sends the 
victim a message "You are being held fast by the Interdictor" and 
you just don't move. No cannon shots happen, but you cannot leave.
