Complete the following tasks to unlock Apple Game Center achievements.

Achievement	How to unlock
100 Enemies	Shoot 100 enemies.
1000 Enemies	Shoot 1000 enemies.
20 Enemies	Shoot 20 enemies.
50 Enemies	Shoot 50 enemies.
Bronze Chalk	Score 25,000 points.
Extra Life	Find the hidden extra life.
Gold Chalk	Score 100,000 points.
Platinum Chalk	Score 1,000,000 points.
Silver Chalk	Score 50,000 points.
Warmup	Score 10,000 points.