Creating interactive decorations

Actors can be made into decorations — not only non-interactive ones, but also interactive ones.

This is an example of a decoration that reacts to attacks and uses actions:

class Pulsar : Actor
{
  Default
  {
    Height 40;
    Radius 20;
    +SHOOTABLE // Will react to being hit by attacks
    Painchance 255; // Will always enter its Pain state sequence when damaged
    PainSound "pulsar/pulse"; // Sound made when A_Pain is called
    +NODAMAGE // Will not actually take any damage from being attacked but will still react
    +NODAMAGETHRUST // Cannot be moved by damage
    +BRIGHT // All sprites of this actor are drawn fullbright
  }
  States
  {
  Spawn:
    HAX7 A -1; // This actor is not animated and shows only one sprite in its Spawn sequence
    stop;
  Pain:
    HAX7 A 15;
    HAX7 B 15 A_Pain;
    HAX7 C 20 A_Explode(flags:XF_NOTMISSILE); // Will deal radius damage, like the Rocket
    goto Spawn;
  }
}

If you want to create a decoration that you can interact with directly, by pressing Use next to it, you can override the actor's Used virtual function:

For example, this odd varation of the explosive barrel explodes immediately when the player uses it:

class OddBarrel : ExplosiveBarrel
{
    override bool Used (Actor user)
    {
        if (user && user.player))
        {
            A_Die();
            return true;
        }

        return false;
    }
}

For more examples and explanation, see the Used() function page.