Remove the Luck component of searching for secret doors and passages. Specifically, change the rnl() calls that allow a search to fail into rn2() calls, which have no Luck bias.

Randomly generated puzzle mechanisms that reveal secret doors once completed. Things such as finding a mechanism hidden under a statue, or having a boulder generate in a room and needing to push it somewhere else in that room.

Kicking a wall where there is a secret door will always reveal the door and will never hurt you. This first kick may WHAMMM or crash it open as usual for doors.

The chance of finding a secret door directly relates to how many seen tiles are surrounding the door. The more tiles around it are seen, the more likely it is to be found.

Realistically, a player searching near a secret door will almost always have either 5 or 8 of the adjacent tiles seen; so perhaps just check whether the player has seen the two tiles on either side of the door. If the player has seen both, finding the door becomes a lot easier.

Scale the probability of secret doors and secret passages in a room-and-corridor level based on its depth, so that level 1 is almost guaranteed not to contain any blocking the way, and the other early levels are also not likely for this to happen.

Improvements to secret doors:

• When the player discovers a secret door, monsters still don’t know about it unless they see it open.
• Monsters know about some secret doors and passages in their native area, and will use them as if they were normal doors/floor. If the player sees a monster traveling through one (defined as being able to see the actual square of the door), it becomes unhidden. The proposed implementation for this is to have some monster types (the Wizard, angels, etc) have full knowledge of all secret doors everywhere, and all other monsters have a bit that represents whether they know about secret doors, which sometimes gets set when they are generated and always gets set when they see some other monster use a secret door. A cruder implementation is just to convert the secret feature into a normal one when used by a monster.
• There are fewer or no hidden doors between the upstairs and downstairs on a Dungeons of Doom level.
• Less of a Dungeons of Doom level’s loot appears on a direct or near-direct path between staircases, and more of the loot appears in rooms hidden behind secret doors.
• Remove secret passages from the game; they don’t add much of relevance and it’s harder to find ways to make them relevant.

Lit candles get snuffed when you move next to an unseen secret door, trap door or hole: “A draft blows out your candle.”

Use the builtin pathfinding algorithm to trace a path between the upstairs and downstairs of each level in the Dungeons of Doom. Along this path, remove or relocate any traps, and (in early levels, perhaps up until the Oracle) convert any secret doors or passages along the path into regular ones.