Experience
When you kill a monster, you gain experience points. After you get enough experience,
you'll gain a level. When you get a level, you get an attribute and a skill point.
You can spend these points to increase your abilities.
Attributes
Strength
Allows you to equip better armor, increases your melee damage.
Dexterity
Increases your reload, weapon switch, and movement speed.
Vitality
Increases your health and medkit power.
Skills
Melee
Increases damage, range, and attack speed with close-combat weapons
Pistol
Increases damage, accuracy, and attack speed with pistols
Shotgun
Increases damage, accuracy, and attack speed with shotguns
Rifle
Increases damage, accuracy, and attack speed with rifles
Heavy
Increases damage, accuracy, and attack speed with heavy weapons