The sequel to Rocketbirds: Hardboiled Chicken, Evolution takes place years after the previous game. Dreaded totalitarian leader Putzki is still alive and kicking, and it's up to Hardboiled to stop him. However, he gets sucked up in a increasingly bizarre conspiracy that involves alien owls and people being turned into food.
Gameplay is quite identical of that to Hardboiled Chicken in a way; but has a bigger focus on combat and less on puzzles. This includes the player being able to aim 360 degrees, as well as being able to jump, aim, run and shoot at the same time. To take advantage of this, there are also dozens of weapons to utilize, ranging from handguns to rifles, to flamethrowers to miniguns. The levels are much more bigger and open ended this time around; allowing for secret areas that hide weapons and costume items.
New to the game is the Rescue Mode, a 4 player online/offline co-op mode where players take control of the budgie commandos from the previous game and, as the namesake, rescue other commandos across four randomly generated themed levels. In game, they can upgrade themselves by finding costumes around levels, and buying weapons from the shops.
This game also includes stereoscopic 3D, enhanced voices in both English and Japanese, enhanced graphics and visual effects and a new soundtrack by New World Revolution.