My RPG game part the second.

Steampunk science fiction.

I really want to make a story about a steam punk planet fighting off a technologically advanced alien invasion, not sure how to though.

First, you plot the end: they lose, aliens win.

Do a post-apocalyptic world where all that remains are myriad steampunk gangs fighting each other over the scraps of non-steampunk technology from our long-forgotten age.

There, problem solved.

The cover should be a man wearing a top hat, shotgun slung over his shoulder, holding a diesel engine carburettor to the sky.

EDIT: Oh, you might want some research materials.
Post apocalyptic fiction - Fallout series
Futuristic gang warfare - Necromunda Underhives
Steampunk - Arcanum: Of Steamworks And Magick Obscura

Just remember, a steam-powered civilisation attempting to use a modern or future level of technology still powered by steam would burn through their world's supply of coal in a matter of months.

wow MM that's a pretty awesome idea, a lot of reference will be from Fallout 1 & 2 and maybe some Necromunda like you said but I have never heard of Steamworks and magick obscura.

There will be four confirmed major races and one fluff race (flavour race)

+ Empire (Humans, supposedly good, Empire defines the armies that fight for the pure humans, that is not to say that there aren't inter city gangs and rivalry, unlike wh40k, man is not unified under a single leader. Patriotism extends only as far as to see other races wiped. The Empire focuses on a steampunk society although they do not depend on coal for fuel. They focus on ranged warfare at a level of technology perhaps of the British redcoat armies of the eighteenth/nineteenth century with the addition of vast war machines.

+ The Black Crusaders (The Crusadium) extending from a fortress floating on magical winds high above an enormous chasm created by a magical detonation. They are bleak, hostile and demonic humans with a deep understanding of dark magic. Again, there is little unity beyond their single name. Many warbands fight independently although many align themselves to one of three gods and this can unify the groups. Less steampunk, this group focuses on magical weaponry, summoning and melee combat.

+ Bayesonians are an elf like warrior race with advanced technology reminiscent of pure mysticism. They engage only in light skirmishes and have little to battle the Empire for although they are rarely allies. It is not known why the Bayesonian incursion has occured. Only that in the last ninety years, many Chaos Craft Cities (a little greek mythology for you there) are drifting into reality.

+ Horde, a race of mutants, created from the after effects of magical radiation exposure. They are slow and lumbering with little singular functionality. Require melee weaponry, they are a salvaging race in that they acquire technology from others. Have access to war beasts like trolls in LotR

+ Derge (name not confirmed maybe Necroderge) Ancient race of humans that dissapeared, only to have submerged as skeletal armies lead by Crusadium Witches and free lance tombraiders. Harness masses of dark energy but tend to use melee weaponry. Practically invincible.

Do the Bayesonians base their civilisation on the practical application of Bayes' Theorem? If not, you're going to disappoint a statistically significant portion of your target market.

What's a Bayes' Theorem?

Google "the way of Bayes", and follow the links on those pages. If you understand it, everything will change.

Maths, my only weakness.

I'm not generally a fan either, but this is worth the effort.

Is it vaguely interesting?

It's fucking revolutionary, especially the full consequences of the methods. Just follow the sequences on LessWrong.

Hokay, will look.

Gah BM, it's just a way of calculating chance and proportionality.

Ha.

No, there's more there. There's a way of thinking that emerges from its use.

I'm sorry, I've derailed your blog.

It's ok, I'm pretty sure it's living only by this conversation anyway.

What do you mean by way of thinking?

That is a series of essays in itself, many of which are already available on Less Wrong that I'm still working through.

Basically, it's rationality as superior to my own as mine is to a New-Ager homoeopath psychic.

http://simple.wikipedia.org/wiki/Bayes%27_theorem

Thank goodness for simpletons.

Sooo... it's like retrospective potentiality? Instead of guessing the future based on the past, we're verifying the past based on the present?

It also helps with statistics in the media and advertisements. Cuts through the crap.