IGN got the scoop on this one (no trailer yet), so I'm gonna' quote the crap out of them:
"Guns Up! is, in short, a real-time strategy game with some tower defense elements."
"It will appear on PlayStation 4, PlayStation 3, and PlayStation Vita, and will support cross-save between the devices."
"You’re given control of an invading army, and your job is simple: make quick work of the opposing army standing in your way, ultimately assaulting and destroying their base of operations. The screen rarely stays static or still from the word go; the battlefield is long, and there’s a lot to pay attention to as you scroll back and forth along large swaths of land, making sure that all is going according to plan as your marauding army makes a beeline for its ultimate target."
"In addition to summoning your troops – who will advance automatically once spawned, won’t stop ‘til they’re killed, and will rank-up automatically if they survive long enough – you can also use special one-time-use items to help level things out. If a tightly-knit group of enemies is giving you a hard time, for instance, you may want to plant a mine in the middle of them to blow them to smithereens. Likewise, your adversaries may be spawning out of tents along one side of the battlefield, necessitating a missile strike to make quick work of them, negating a point of entry for your opponents’ soldiers. If your soldiers are getting cut down and you want to regroup and spawn more behind them, consider planting a rally flag to get everyone together and on the same page."
It'll be free-to-play, and "Guns Up! can be played without spending a dime, and it endeavors to completely avoid the pitfalls of the dreaded “pay-to-win” trap. Microtransactions will allow for the purchase of cosmetic changes, some upgrades, and more, but they’re never necessary."
Well, we'll see about that. More screens!