

\section{About}
\subsection{General}
It is the year 2084. You control a secret organisation charged with defending Earth from a brutal alien enemy. You will need to build up your bases, prepare your team, and dive head-first into the fast and flowing turn-based combat.

% Right, so what's the twist?  Extended gameplay, more features...?
UFO: ALIEN INVASION is a squad-based tactical strategy game in the tradition of the old X-COM PC games, but with a twist. Our game combines military realism with hard science-fiction and the weirdness of an alien invasion. The carefully constructed turn-based system gives you pin-point control of your squad while maintaining a sense of pace and danger.

Over the long term you will need to conduct research into the alien threat to figure out their mysterious goals and use their powerful weapons for your own ends. You will produce unique items and use them in combat against your enemies. If you like, you can even use them against your friends with our multiplayer functionality.

`UFO: Alien Invasion'. Endless hours of gameplay -- absolutely free.\\

% Does this para belong farther up maybe?
The game takes a lot of inspiration from the X-COM series by Mythos and Microprose. However, it's neither a sequel nor a remake of any X-COM or other commercial title. What we, as a team, wanted to make is a brand new experience that tries to surpass the quality of games from 1992, rather than to simply recreate them with flashier graphics.

We also believe that open-source projects don't need to be disorganised or badly-managed. We work together in a friendly and professional way, with a clear vision for a game that we know is worth playing.

\subsection{Typographical and Other Conventions}
Since this is a manual for computer software, I will use conventions from popular computer books to denote things like file paths and commands.

\textbf{Boldface} --- interface elements such as buttons.\\
\emph{Italic} --- filenames, names of screens and modes.\\
\texttt{Fixed width} --- chapter names within main body text.

Also, while we recognise that gamers come in all shapes, colours, sizes, and sexes, for brevity's sake, this manual will always use the male gender when discussing the players themselves or the soldiers.  Women, please do not take this personally.

\subsection{Gameplay}
Like the original X-COM games, UFO:AI has two main modes of play: \emph{Geoscape} mode and \emph{Tactical} mode.

In \emph{Geoscape} mode, the game is about base management and strategy. You manage the activities and finances of PHALANX, controlling bases, installations, aircraft and squads of armed-response troops. You'll research new technologies and use their results in battle against the aliens. You'll launch your interceptor aircraft to shoot down UFOs and dispatch dropships in response to alien activity across the globe. You can build, buy and produce anything you like, as long as your technology level and your budget will allow it.

\emph{Geoscape} mode employs easy-to-use buttons to control the passage of time however you like.  Gameplay will  automatically pause whenever there is an important message for you to see. As time passes, your research will progress and your workshops will produce items, all under your guidance.

In \emph{Tactical} mode, the game is about taking command of your team during missions to combat the aliens. Instead of pushing impersonal armies around on giant maps, you use only the team of soldiers you've assigned to deal with this mission -- the same soldiers you've managed and equipped in the \emph{Geoscape}. You may find civilians and other bystanders during the mission, either being targeted and executed by the aliens or just getting in the way. It's a dangerous world, and some of your men will die.

\emph{Tactical} mode uses a turn-based system, where your team and the aliens take turns to move. During your turn you can order your troops to move around, fire their weapons, throw grenades or use other equipment, etc. Each soldier gets a certain number of Time Units (TUs), representing the total time they have to act during the current turn. All actions in Tactical mode require TUs to perform. Once a soldier is out of TUs, he or she can't do anything more until the next turn.

Your mission objectives will vary for each mission, and there are many to perform as the aliens' terrifying plot unfolds. You'll have to watch your back, be quick on your feet, and take the fight to them.

If you cannot, humanity is doomed.

\subsection{Game Engine}
The game engine is based on a heavily modified version of ID's Quake2 Engine. This doesn't mean that `UFO: Alien Invasion' is a modification or even a total conversion of Quake 2. It is a stand-alone game and doesn't require Quake 2 or any other program to run. All you need to play UFO:AI is a computer running Microsoft Windows, a supported version of Linux, or MacOS X, and an installer from our website.\footnote{\ufohomepage}.

Our updated engine has modern OpenGL graphics and special effects, increased texture resolution, hardware-accelerated clipping of map layers for toggling between levels, a new animation system for player models, powerful artificial intelligence, and many other exciting features.
