The Darkness/Gameplay

Options
You can change the controls, lighting, and aiming sensitivity and aid through the menus.

Difficulties
Difficulties will affect how quickly you and your enemies die. It also affects whether or not you will be eligible for the two difficulty related achievements (only available to Normal and Hard).

The Darkness
There is no darkness meter, so you'll have to be conservative when thinking about how much darkness power you have. If you're in the light, you are losing power. If you're in the dark, you will see the tentacle serpents sucking up darkness. If you can't bring out the darkness, you're either in a pacifist area, or out of power.

When the darkness is present, it will absorb some of the projectiles that would normally hit Jackie. If it takes damage, it will lose some of its power until it eventually retracts. You can restore power to the darkness by standing in shadows or a dark area, or by devouring hearts.
 * Darkness Shield

After acquiring The Darkness, killing humans allows you to eat their hearts. If you find a random corpse, or if you kill a civilian, you may not be able to eat their heart. Walk up to a corpse and press when the prompt appears. You can also devour hearts using the Creeping Dark.
 * Devouring Hearts

These are demons that you can summon from little portals on the ground (the portals look like glowing white manholes with tentacles coming out of them. After using a portal, it turns bright blue.
 * Darklings

The creeping dark is a darkness power. It allows one of the tentacle serpents to drop to the ground and crawl around. You gain control of it when this occurs. You can crawl over walls, through small passageways, instantly kill enemies if they don't attack the creeping dark, and also devour hearts.
 * Creeping Dark

Weapons and ammo
When you press, you will drop your weapon rather than reload it. Conserve your ammo if you can.