Press [F1] to see the explanation of the controls in game. Most controls have an "energy cost". Energy is required to do anything.
[Arrow keys] to move, hold [Shift] to move several tiles at a time. Press [Enter] to descend in to the local area you are on (if possible). [Backspace] to go back out. The furthest you can "zoom out" is the super-galactic view (where you can clearly see the spiral shape), the closest is the planetary view (where you see 'o' for rocks).
You can press [Tab] to "scan" for objects. This is most useful in a planetary system, as it will show you where planets and space stations are. It is also useful for the super-solar view, where it will tell you the closest npc ships are. You can press [S] to toggle scan mode, but that isn't actually useful.
You can launch [M]issiles after scanning in a view. This lets you combat npc ships. You'll need a few to take them down.
With the [E]nergy Converter you can convert certain resources directly into energy. With the Mass [F]abricator you can create certain tools from energy.
You can [D]eploy a navbeacon, which basically creates a checkpoint you can teleport to. Press [G] and select a navbeacon to teleport to it.
For controls with a "Choose BLAH" you can press the control again and it will close the menu.
Interaction with space stations is: you step on the + or -, press [Space Bar] to do the corresponding trade (+ is buy, - is sell). I haven't found a way to interact with merchant ships yet (other than to blow them up).
The idea of the game is to explore the universe and get resources. On certain planets when you descend low enough you'll find resources which you can step on and press [Space Bar] to pick up. They go into your cargo, and you can sell it or convert it to energy. There are upgrades you can get for your ship to help your journey. I believe the point of the game is to explore, but there are currently not many incentives to continue exploring. There are rumors that you can win if you find a certain artifact. But good luck, there's billions of stars.
I guess the goal of the game is to reach the X at the center of the galaxy, which requires enormous amounts of energy.
(If you can't find the X, it's because you're not at the highest level, press backspace until you see it)
I think if you're by a red thing, go away from it until its little red arrows disappear. You can shoot missiles at it by pressing Tab to scan then M to arm the missiles...
For those that missed it, there is a downloadable version as well: http://www.infiniverse-game.com/ (Interesting side note, the downloadable version was written in FreeBASIC.
I think this is a great start.
There are some goods you can find to buy with your initial money, though many (from what I've found) are too expensive.
The only win condition that I'm seeing is reaching the center of the galaxy.
But it is very cool to see an online version.