Kill the first enemy.
Kill 1000 enemies.
Kill 7500 enemies.
Complete the mission with 100 accuracy.
Take 100 headshots
Take 1000 headshots
Upgrade your Pistol to the maximum.
Upgrade your Dual Revolvers to the maximum.
Upgrade your Tommy .45 to the maximum.
Upgrade your Shotgun to the maximum.
Upgrade your Minigun to the maximum.
Upgrade the defensive walls as much as possible.
Complete the first episode.
Complete the second episode.
Complete the third episode.
Complete all episodes.
Get 10 stars total.
Get 40 stars total.
Get 80 stars total.
Get 120 stars total.