Under Defeat is a 2.5D shoot em up featuring helicopters.
It has pretty impressive graphics and sports some nice little physical effects (like trees waving back and forth because of a detonation).
On the gameplay side the game doesn't impress too much, however.
It's a pretty standard and straightforward scoring system, you blow all stuff up > you win. Blow up some enemies at once to get more points.
Thats pretty much it, but the game still is a lot of fun and a blast to play. Don't expect too much substance in it, though.