I'll preface this by saying that I didn't play Just Shapes & Beats on the PAX showfloor, but that didn't stop it from being one of the coolest things that I saw there. And that a lot of people saw there, apparently. There was always a ridiculous line of people standing around the booth, crowding the TV, and trying to get to be one of the next to play. For being extremely vague, the title of Just Shapes & Beats is also a perfect description for what's going on in the game. As a driving electronic score plays, you control your little ships around an incredibly hostile environment, where shapes pop up on the screen and try to kill you. And maybe that sounds overly simplistic... maybe it's better to see the game in motion.
It's like a bullet hell shooter set in this bizarre, hostile world that is brought to life by music and it all just wants to kill you. It looks incredible and I appreciate the way the pieces move around, and the sudden violentness with which they lunge at you. The big screen-crossing rectangles are especially good for that feeling, and the look of the pink shapes on the dark background pops super well.
The mechanics are as simple as the name. You don't go on the offensive, you're merely working to avoid dying by flying around. Even the boss level they had on display at PAX, you never attacked, and in the end, the boss wound up destroying itself as you dodged around. Since the levels are pattern and music based, a couple of playthroughs and even the most difficult ones should fall into place.
To make things a little easier you also have a dash move, and you're invincible while you're dashing, giving you a little more leeway and a better ability to get out of the way. I believe your ship can take multiple hits (depending on what said hits are - some seem stronger than others), and if you die in multiplayer, you can be revived by a partner.
There really isn't much to say about Just Shapes & Beats because the beauty of the game is in the experience of watching and playing it. That video above says a lot more than my words can - a simple description of the mechanics at play is difficult for a game that's so much about the experience that marries the visuals and sound and frantic pace of your little ship running around to escape from a sudden musical explosion.
Also their swag included a coaster which was... unusual.
Just Shapes & Beats is one of those games that you can get so much out of from just watching, and playing it looks to be difficult, but rewarding in the way only these kinds of music-based games can. Dodging to the beat, moving around the level, dashing to escape an onslaught brought on by a bunch of electronic noise is the kind of synesthesia-driven fun that's helped games like the Bit.Trip series be so enjoyable.
There doesn't seem to be a release date yet, but Just Shapes & Beats' website has a link to where you can go and watch them build the game. I'm not sure if there's any plans to have it dynamically create levels based on your imported music, but the levels they're personally creating look awesome and you should really see and play this game.