Skill level

Skill level determines the overall difficulty of a game - how many monsters and powerups are out there, how much ammo various items give, etc. There are 5 of them:
 * 1) Determines the number & type of things in maps. This means that skill levels of the same class have the same number and same types of monsters and items. The difference mainly amounts to more and bigger monsters on the harder skill levels, but in some maps this is used for other effects; for example, in E3M6: Mt. Erebus the blue key is located in different places depending on the skill level.
 * 2) Ammo powerups give twice as much ammunition as they do on other skill levels.
 * 3) All damage the player(s) take is halved.
 * 4) Monsters respawn 8 seconds after being killed. This modifier can be used with any skill level using the -respawn command line parameter.
 * 5) All monsters attack more often, Demons move & attack 2 × faster, Imp fireballs are 50% faster and Cacodemon, Hell Knight & Baron of Hell fireballs 33% faster. This modifier can be used with any skill level using the -fast command line parameter.