Time limited puzzle game?
You run around to amass groups of animals, each with different skills (gators can make water bridges, monkeys can climb over walls, etc) and different 'attack' power (monkeys have 1, gators have 2, elephants have 6, etc). The basic goal is to collect enough animals to beat up aliens (that each have 6hp so far) that are slowly waltzing towards your precious egg before they get there. Every level is pretty different given the constraints, I'm surprised at the variety after about 25 levels.
The multiplayer is funny - basically it's a race to collect animals and then trash your opponent by having collected more and then mowing them down. It's goofy and quick and fun with very little strategy.
Some of the trophies are pretty fun too - eventually there's levels where you 'birth' baby animals in green grass - if you walk over yellow grass they become adults. One trophy is to finish a level so only babies are left (meaning you have to wipe out the last alien with your last adult animal). The collectibles seem pretty painless too - they've been mostly visible so far and there's not too many.
So basically what mpaullin said.
Edit - it's also quite crashy and sometimes corrupts saves