The Steam page for it appears to be busted: http://store.steampowered.com/app/233250/
But there was recently an update called 'Titans' here: http://store.steampowered.com/app/386070/
About the Game
Colonize solar systems, annihilate homeworlds, and exterminate your foes in epic interplanetary battles with multiple players and thousands of units. Planetary Annihilation takes strategy gaming to a never-before-seen scale — and gives players powerful tools to control the action.
Blow up everything, anywhere; dominate with punishing spacecraft, robots, and other futuristic machines of war. Arm asteroids and send them on planet-destroying collision courses. And take over an entire galaxy in a dynamic single-player mode with procedurally generated content. Don’t just win, annihilate!
Key Features:
Epic Single-Player - Galactic War is a twist on traditional real-time strategy campaigns that has players battling across a dynamic galaxy filled with procedurally-generated content. Every playthrough is different. Annihilation is final.
Epic Multiplayer - Play with up to ten friends (or enemies) in massive free-for-all and team-based matches.
Spectate And Broadcast - Spectate matches with a suite of incredible viewing options or broadcast with integrated Twitch.TV support.
Advanced Command And Control - With intuitive drags and clicks, seamlessly switch between planets, mine resources, create custom unit formations, or pulverize armies.
Dynamic Picture-In-Picture - View and interact with your units on another planet in a second window as you focus and control the action in your primary view.
Instant Replays - View in-match recordings in real-time while matches are in progress. See when a battle turned by rewinding the game to any point or check out the entire match after a game ends.
Smash Planets - Don’t just win, annihilate. End games with the mother of all weapons: an asteroid on a collision course.
Those that bought it yesterday for $4.99 in the Humble Store might be kicking themselves :P