I love this classic. Before I ever played Sim City, before the first of the Civ’s were made, there was Supremacy. The idea is simple. Two rulers and one solar system resulting in a fight for the Supremacy!
You start off as a human, owning a home-world, with a certain population and a certain amount of money. This world is on one side of the solar system, and on the other side is your enemy! All other planets are dead, and simply await your colonization. You will need to buy a teraformer in order to create conditions suitable for sustaining life on such planets. You have some money, but it will run out quickly. Your only income is the tax paid by your people. But don't raise them too high, or else your population will shrink.
For your population to grow you will also need food, energy and minerals, so you need to buy ships that can mine those goods. And while you’re at it, it's smart to also buy a transport ship in order to move people to newly teraformed planets and see them flourish.
Now once that is done, you’ll already be a thorn in your opponent’s …err, part of the body they use for the visualization, so you can prepare your self for war! This is the only part of the game I’d change. You don’t actually fight. You must train your soldiers, equip them and send them to defend or attack a planet. But look out, if you fail, it takes quite some time to fully train a new outfit and your opponent has a stronger force defending his home-world then you can muster up in one go!
So, who’ll rain supreme in Supremacy?