Instead of making all trapped doors explode and stun the player, add more varied door traps. The trap should be determined based on depth. It should also be selected deterministically based on the coordinates of the door (a convenience so that a trapped door will always have the same trap effect without having to store which trap it is.)

Additionally, new traps can also be used with more door states, rather than have all traps trigger by trying to open the door. Nondestructive traps could also remain on the door until the door is untrapped, rather than vanishing.

An interesting addition would be if doors were made restrictedly or completely untrappable, in order to prevent optimal strategy from being attempting to untrap every door that the player comes across. Or possibly an attempt to open or close a door should do a cursory trap check.

List of door traps in rough order of minimum depth necessary to generate them:

• The hinges screech loudly when opened or closed, waking nearby monsters.
• Door closes and locks itself.
• Electric shock from the knob, dealing 1d(DL*2) damage, that doesn’t destroy items.
• Bucket of water falls on your head and causes water damage to several items in inventory.
• Your hand is stuck to the knob, causing you to be unable to move for the next few turns.
• Hingeless door: either falls on top of you and deals 1d(DL/2) damage, or (more likely) falls the other way and you fall over on top of it. Either way, you are stunned for a few turns. The door becomes “broken”.
• A boxing glove swings out from behind the door and punches you, dealing damage and causing you to stagger/hurtle back a few steps.
• Object falls out of the ceiling on the player’s head (copying an ADOM trap).
• Knob burns your hand for 1d(DL) damage and causes you to drop your weapon. Gloves reduce damage and prevent the drop.
• Door that explodes in a fireball: possibly no stunning, but burns inventory as it does in GruntHack.

Ring of opening, which unlocks locked doors and boxes instantly while you are wearing it and try to unlock them. If blessed, it additionally untraps doors and boxes when you try to interact with them, but there is a fixed chance it unblesses in the process every time it untraps something.

While you are carrying the Master Key of Thievery, all door and container traps that you would have triggered are automatically removed without any triggers and probably not even any message indicating a trap was disarmed. If you actually want to trigger these traps for some reason, you can drop the Key or put it in a bag.

Possibly, these effects are suppressed when the Key is cursed (for rogues) or non-blessed (for non-rogues).

Instead of storing door traps as part of the door state, use the trap field of struct lev with a special new DOORTRAP trap to indicate that there is a trap on the door space.

Open doors can generate trapped. When you step off an open door to some other space, it closes and locks behind you.

Zapping the wand of opening (but not the spell of knock) at a trapped door will cause it to blow up.

Alarm trap on doors: it makes a noise to alert nearby monsters, and also summons a squad of ogres or Kops or whatever on one of the stairs.