Complete the following tasks to unlock Apple Game Center achievements.

Achievement	How to unlock
1000 Kills (100 points)	Kill 100 enemies in career.
10000m (100 points)	Reach 10090 meters in a game.
1000m (25 points)	Reach 1000 meters in a game.
20 Kills (25 points)	Kill 20 enemies in a single game
2000m (50 points)	Reach 2000 meters in a game.
50 Kills (50 points)	Kill 50 enemies in a single game.
5000m (75 points)	Reach 5000 meters in a game.
Back Attack! (25 points)	Attack an enemy from behind.
Comeback (50 points)	Come back from a desperate situation.
Kill Them All (50 points)	Kil all types of enemies in a single game.
Marathon (100 points)	Cover a distance of 42195 meters in career.
The Pacifist (50 points)	Don't kill anyon in a single game (but run at least 300m points).