This tutorial will show you how to detect the skill level in vanilla Half-Life (requiring no custom code), and using the information to change the map's entity composition e.g. higher skill == more monsters == less items.

This tutorial assumes that you are familiar with the following concepts:

• Using TriggerTarget and TriggerCondition attributes on monsters
• Relays (trigger_relay) and killtarget
• Globals (env_global) → Tutorial: Globals for refresher

Overview

Suppose we want to set up a map or campaign that has the following entity composition: Whereas Half-Life entities have a reserved global spawnflag value: 2048 - Not in deathmatch, which removes the entity if the map is run in deathmatch, unfortunately there is no flag to make entities spawn only at certain difficulty/skill level in the vanilla codebase.

However, we can set up some entities to detect the skill range i.e. whether we're at X skill or higher/lower depending on the method used. The detection mechanism depends on a monster having differing health based on skill level (set in the skill.cfg file). The output of the setup is then used to do some other map logic; in this case removing certain monsters and items.

We'll be using the alien grunt, the only monster in vanilla Half-Life with differing health per skill level. The following snippet from skill.cfg sets their health:

// Alien Grunt
sk_agrunt_health1    "60"
sk_agrunt_health2    "90"
sk_agrunt_health3    "120"

The skill detection setup hinges on a monster's ability to trigger targets according to set condition (the TriggerTarget and TriggerCondition attributes); specifically when their health drops to 50% or 0. For this we will be inflicting the monsters with specific damage values that either trips or skips the set triggers depending on the skill level.

Methods

Method 1: Upper bound detection (X or lower)

This method is used to detect if the skill is below a certain level. Suitable for having more monsters in harder skill levels.

In the starting map (i.e. the starting map when you start a new game), place 2 alien grunts in a room, separate from the rest of the map (far away from the info_player_start or you'll hear them cry in pain or die). They will be set to trigger specific target when they die. Next, we will set up the strategic pain inflictors that does, um, inflict specific amount of damage. In this case, two doors each set to deal damage slightly below the medium and hard health levels, respectively. We will also be placing trigger_auto's to activate these doors as soon as the level starts. Note that each door name has to be unique – for some reason this setup will not work correctly if these pain-inflicting doors share the same name. Needless to say, the door must be set to move in a direction that crushes the monsters. Compiling and running the map at this point in our setup should produce the following outcome at the start of the map:

• On easy, both alien grunts die (60HP < 89dmg < 119dmg), triggering both TriggerTargets (BelowMedium, BelowHard)
• On medium:
  • Monster #1 survives (90HP - 89dmg = 1HP), skipping BelowMedium
  • Monster #2 dies (90HP - 119dmg < 0HP), triggering BelowHard
• On hard, both alien grunts survives (120HP > 119dmg > 89dmg), skipping both TriggerTargets

Now we can capture the events that fire based on the skill level or range. To fire the events on the same level, add the following entities: To store and use the result on other maps in the campaign, we will need to use global states. In the same map as the setup, add these entities: Then in all other maps, add these entities:

Method 2: Lower bound detection (X or higher)

This method is used to detect if the skill is above a certain level. Suitable for having less pickups on higher skill levels.

Add these alien grunts: The doors should inflict damage slightly higher than the alien grunt's health in easy and medium skills. The setup outcome should be as follows:

• On easy, both alien grunts are killed (60HP < 65dmg < 95dmg), skipping both TriggerTargets
• On medium:
  • Monster #1's health gets reduced (90HP - 65dmg = 25HP) to below 50% health, triggering AboveEasy
  • Monster #2 dies (90HP - 95dmg < 0HP) , skipping AboveMedium
• On hard:
  • Monster #1's health gets reduced (120HP - 65dmg = 55HP) to below 50% health, triggering AboveEasy
  • Monster #2's health gets reduced (120HP - 95dmg = 25HP) to below 50% health, triggering AboveMedium

Use and store the outcome in the same map as the setup like this: Use the global state in the other maps as follows:

Combination

The two methods above can be combined. Do note that both methods have trigger_relay's and trigger_auto's that can fire targets on medium skill, so use them from only one of the methods, or you'll end up firing those targets twice on medium skill.

Notes

• Starting map is set in liblist.gam.
• Having the setup as global states makes this setup unaffected by players manually changing the skill level partway through the campaign via console commands (which they shouldn't be doing anyway.)
• The global states reset if a map has "New Level Unit" set to yes. If you need to set a new level unit, you need to add the setup again.
• Alternatives to basic killtargetting of the entities:
  • Use the trigger_relay's and trigger_auto's in Method 1 to target a monstermaker that spawns monsters/weapons/ammos/items in its stead.
  • Use Method 2 and the killtargetting of func_breakable's which in turn spawn the desired weapons/ammos/items.
• Allow for all the entities for all skill levels to exist for a split second at the start of the level, as the setup takes that fraction of a second to do its thing. Have the player spawn facing none of the affected entities, for instance, or make the level fade in in worldspawn.

Vault

See also

• Tutorial: Non-coding workarounds for your mod