NEBULON INVADERS
-------------------------------

The Story
-------------
The citizens of the planet Nebulon are a proud and warlike people.
One fateful day their scouts reported the results of a survey of
the planet Earth. They warned that if not dealt with, Humans could soon 
usurp Nebulonians as the prime warmongers of the galaxy. The Nebulon
council was in a tumult, until one of the most aggressive of their number
suggested what the others had all been secretly thinking. The only
reasonable course of action was to hit the Earthlings so hard that they
could never recover.

An invasion force was dispatched, with orders to enslave the populace,
but they had reckoned without the presence of a lone Earthman, who was
the only one not to be filled with fear. He was in fact a coward, but at
that moment he was too drunk to recognise the risk he was taking. He went
down to the army surplus store and purchased the most powerful missile
launcher he could afford with the loose change in his pocket, and set out
to save his planet from the terrible fate awaiting it.


About the Game
---------------------

This game was written for the BlitzCoder Space Invaders competition, and
was awarded 'most original game'. It adheres to the standard Space Invaders
formula, but there's a twist. Rather than sitting at the bottom of the screen and
shooting upwards all the time, your gunner is positioned on the Earth, and you
can move 360 degrees over the surface.

Invaders still come down in waves, but they are now aiming for the sphere
of the Earth, rather than a straight line, and so their angle range becomes
greater the closer they get to the surface. The more invaders you destroy
in a single wave the faster they move, and the more bullets they fire. Once
you've destroyed most of the invaders on screen (or a certain amount of time
has elapsed) a new wave will appear, coming in at 90 degrees to the last one.

Because this is not a single screen game, there is a map in the top right
corner, which gives you an overview. This allows you to respond to the
threat of each new wave, and also to track the Mothership. The Mothership
appears at random, and the sound it makes will reveal when it is about.
The Mothership fires bullets as well as the regular invaders, so beware!

The defensive fortifications of Space Invaders appear in this game, spaced evenly
over the Earth's surface. Enemy shots (or your own shots) will cause minor damage,
whereas if an invader gets low enough to crash into one, that defence will be destroyed.

At the start of a game you have 3 lives, which you can lose in any of the following ways.

1. Being shot by an alien's bullet.

2. Being caught in an explosion. This could be any type of explosion, caused by an enemy
bullet hitting Earth, a crate hitting Earth, or an invader colliding with one of your forts.

3. Colliding with an alien itself. If any aliens get this close to Earth there's little you can do
except stay out of the way and pray for an Earth Defences power-up.

4. Allowing an alien to invade. If this happens then you lose a life automatically.


Scoring
----------
Red invaders score 15 points, Green invaders 30 points, and Blue Invaders
50 points. Other invaders may score up to 100 points, and hitting their
shields scores 5 points for each hit. The Mothership score varies depending
on the accuracy of your shot.

When you destroy the last invader in a wave, you will be given an
accuracy bonus for your recent performance. Each enemy bullet that hits
the Earth causes you to lose 2 points, so it's advisable to clear each
wave quickly. Also don't leave the most deadly invaders in each wave
until last, or their rate of fire will become incredibly high.

If you do well enough, you earn the right to enter your name into
the Hall of Champions.


Controls
-----------
KeyBoard Controls are as follows.

Left Arrow	- Move Left
Right Arrow	- Move Right
Space Bar		- Fire/Unpause/Start/Restart
Down Arrow	- Pause/Unpause
Escape		- Escape

Joypad Control are as follows.

Left (dpad or analogue pad)	- Move Left
Right (dpad or analogue pad)	- Move Right
Button 1			- Fire/Unpause/Start/Restart
Button 2			- Pause/Unpause
Button 5			- Escape

You can escape using either method, regardless of the control setting.


Toggles
----------
There are 3 toggles, which can be used at any time (apart from when you're
entering a high score).

Key A (or Joypad Button 6)	- Turns the Autofire On/Off
Key M (or Joypad Button 4)	- Turns the Music On/Off
Key C (or Joypad Button 3) 	- Switches Between Keyboard and Joypad Control

A message will appear at the top of the screen to confirm your selection.


Item Crates
---------------
These will regularly drop in from space to power up your gunner. They can come in from
any angle, and are heralded by a sound effect, and are indicated on the map screen. The map
screen is critical in allowing you to pinpoint where the crates are, so that you can intercept
them in time.

If you shoot the crates, or the invaders shoot them, or they hit the Earth, they will explode,
and you will have lost the chance to get a power-up. However if you sit underneath one
you can collect it, and receive a random surprise. Each power-up lasts for 15 seconds.

Note - If your power-up is a shield you will retain it after the 15 seconds are up, but it
will no longer re-charge.

WARNING - Crates are helpful but they can also pose a danger. If you go for a crate but
are too late you may be caught in the explosion which occurs when it hits the Earth. It's
important to know when to pull out, as well as when to go for the crate. If you lose a life
you will also lose any upgrades, so be careful.


Power-ups
--------------
Here's a rundown of the power-ups you can receive. They are all equally likely to appear.

SUPER SHIELD 	- A fully powered shield, which recharges slowly.

TRIPLE FIRE 	- Three shots fire off in parallel, to devastate the aliens above you.

SPREAD SHOT 	- Three shots fire at 45 degrees to each other.

RAPID FIRE 	- A much faster shot than before. Mow the invaders down.

CRATE SHOWER 	- Greatly increases the number of power-up drops.

HYPER SNIPER 	- Speeds you and your bullets up, and allows you to fire behind your defences.

SPLIT SHOT 	- When you hit an invader (or shield) more bullets will be generated, causing a
		devastating attack to be unleashed. Best used on groups of densely clumped
		invaders.

SLICE BULLETS 	- Carves through alien ranks like a knife through butter.

EARTH DEFENCES - A giant yellow forcefield surrounding the Earth. Keeps out bullets, and destroys
		any aliens inside it. The only thing that can kill you now is a crate explosion.

SIGNAL BEACON - Causes crates to be directed with great precision to your exact location.

FORTRESS GUNS - Your fortresses all fire shots regularly, unless they are badly damaged.

SHIELD CHARGE - Charges your shield up to half strength, and continues to charge strongly.
		Make sure you don't get hit before the charge is complete.

DEEP FREEZE 	- Stops all invaders in their tracks, and jams their weapons systems. This also
		delays future waves, buying you some time.

TRIPLE SCORE 	- The screen glows pink. Any invaders destroyed during this time will earn
		you triple points, including the mothership (this doesn't apply to bullets fired
		by fortress guns).

Note - All these power-ups can be used in combination with each other. The only exception is
that the Crate Shower and Signal Beacon power-ups can't be combined with each other, so if
you collect one then the other is immediately de-activated.

