Sin Episodes Level Creation/Personal Challenge System: Single Player

NPC Rules

Unlike arena mode, where every enemy is upgraded from or downgraded to the regular pistol grunt, enemies are only allowed to spawn up to one level away in single player.
For example, an npc_druglab_grunt_pistol can upgrade to an npc_druglab_grunt_scattergun, but not an npc_druglab_grunt_assaultrifle.
Likewise, an npc_druglab_grunt_elite can downgrade to an npc_druglab_grunt_assaultrifle, but cannot downgrade any lower.
Jetpack grunts (npc_druglab_jetpack) cannot upgrade or downgrade.

Mutant NPC's cannot spawn up or down on their own. However, if you use the info_challenge entity, you can force that behavior.

By default, spawns linked to an npc_template_maker are going to use the dynamic difficulty system to modify the number of enemies created.
To disable that behavior, set the Don't use dynamic difficulty flag on the npc_template_maker. You should also set Don't Spawn While Visible.

The crates found throughout SiN Episodes are also hooked up to the Personal Challenge System. To use these crates in your levels, create item_item_crate entities in the appropriate locations.
By default, the crate that you create will spawn items of type item_dynamic_resupply, which is where the Personal Challenge System looks at what you need the most, and put that in the box when you break it. You can force a specific item to be in the crate by changing the Item Type keyvalue.

The info_challenge entity allows you to change the way that the game plays based off of the initial challenge level selected by the player, the current challenge level, and the amount that the challenge has changed since the game started.
For single player, there are many possible ways that you can use the info_challenge entity in your favor. You can add or remove environmental obstacles, lengthen or shorten major encounters, and more.