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Traps

Name dcss:brainstorm:misc: Traps
Summary About dungeon traps and the Traps&Doors skill
Further information Trap creation from wands http://sourceforge.net/tracker/?func=detail&aid=2579528&group_id=143991&atid=757516
Added by b0rsuk
Added on 2010-09-13 19:10
Overhauled 2011-10-10 by dpeg

The problems

  • Mechanical traps (dart, needle, axe, nets etc. traps) are often uninteresting: If you run into one, most often you get a little damage, rest it off and keep going. Sometimes, you will die (for example to a blade trap). While we can always blame the player for running around with non-full health, or having not enough T&D skill for her maximal health, those deaths are not fun.
  • Mechanical traps don't even work well when monsters are around: If they make you die, it's still a bad death. They serve a point in places where the players knows he is walking in a minefield, as e.g. in Tomb or some vaults.
  • Worse, players could feel encouraged to explore very slowly in order to reduce chances for trap incidents. However we change traps, we must ensure that autoexplore is as good as before. A similar is issue is players being able (in principle) to keep track of all squares they've been on or they've seen monsters step on. Those traps are currently safe from traps.
  • Shafts and Zot traps are very interesting, even without any monsters. They are still prone to the potential grind from above.
  • The T&D skill is currently only used to passively avoid the few dangerous traps. There is no incentive to train it very high.

Pressure Plate Traps

I don't know if anybody is still using this place here, but if they are, I'm in the most recent trunk version (27 Jun 2016) and I found a trap that was simply a pressure plate. Once stepped on, a grate cut off my escape and sent a rolling boulder beetle after me. This, I think, is brilliant, and should be very vastly expanded upon. Traps like these, I mean. If they were harder to detect, that'd be great too. The shafts, teleport traps, zot traps, alarm traps… All those are fine and good too, but special traps like as described above are an inspired idea and there ought to be more of them.

Newer, more radical proposal

The three types of traps

  1. Vault traps: Those are created during level building and only from vaults. No more random placement!
  2. Spawn traps: Those are generated on the spot as the player encounters monsters.
  3. Standalone traps: Those are interesting on their own, e.g. shafts or summon traps or Zot traps.

Spawn traps

  • Spawned traps are generated as you explore. After creation, they can be detected as usual.
  • Spawned traps are only generated in the vicinity of some monster(s). (No more than LOS distance.) The trap belongs to the monster(s). If all those monster(s) are killed (or off level), then the trap is wiped out as well.
  • Spawn traps are never of the mechanical type. (Dying in a trap is no fun, not even if monsters are around.)
  • All traps make noise.
  • Monsters (of any type) don't trigger undetected traps (vault or spawn), they can walk right over them.
  • As long as the monster(s) are alive and around, they can create traps. (More technically, being in sight of a monster can lead to a trap being spawned.)
  • Chance and trap types depend on monster type, depth and branch.
Example:
......#   Upon seeing the ogre, you will want to engage it. 
.@...O#
......#   If you move towards it...
  
......#   ...a trap like the marked one may be spawned. You can proceed slowly (walk, wait etc.)
..@^.O#   but then you have less time to pelt the ogre with stuff. Or you can press onwards and
......#   suffer a little (net, additional summons, item loss, noise).
  
^.....#   You can try to avoid this by luring the ogre towards you. However, then a trap may still
.@..O.#   spawn in your vicinity. This is of no concern against a lone ogre like here (you kill the
......#   ogre and the trap disappears if not yet detected) but ogres come in bands.

Standalone traps

Traps which are interesting on their own (i.e. without monsters) like shafts or summon traps can use a special ruleset (some care is needed to make it scum-proof and to avoid punishing players who use autoexplore):

  • During level building: For each trap to place, mark a zone (not necessarily connected) large enough so that removing it breaks the level into (at least) two sizable pieces.
  • Stepping onto any square of the zone has a chance to trigger the trap right away (i.e. only a single attempt at trap detection).
  • If the trap is detected or triggered, clear the zone.

Reasoning: We don't want to place standalone traps in advance (i.e. during level building) in order to prevent players from boring themselves by slow exploration.

Example:
#########################################    A miniature Crawl level. Some potential zones are indicated:
#.<.....#.....11..######.........########    
#..##.#.#.....11.....####..............##    Suppose 1 is for a shaft, 2 is for a Zot trap.
#...###.#.##..##.......##........####..##
#.###....##...##..............#####....##    Entering any square marked 1 triggers a T&D check.
#.............11....####..#......#....###    After the check, no other shafts are tested - all 1 marks are
#.####........1########..#.#..._.#...####    removed. Same for all 2 squares. (The zones could overlap.)
#.#..#....##############..#......#.....##
#.#..+.....##############.....######...##    The idea is that no matter how you explore (even if extremely
#2#22#2222222#####2222##2222222222222222#    conservatively), you will have to cross the zones.
#.#..#..........1.......................#
#.####..........1............##+++##....#
#...............1............#.....#....#
###+############1............#.....#....#
#..............+.............#..>..#....#
#..............#.............#.....#....#
#########################################  
I like the idea, but the zones themselves may need some thought. I feel as though using a wall-to-wall strategy as presented above could still cause players to alter their behavior, with the rationale being that if they fully skirt the perimeter of a level before heading inward, they're guaranteed to not hit any standalone-type traps in the interior. Perhaps better to define zones as irregularly-shaped, contiguous regions, like so:
#########################################
#.<.....#.....2222######.........########
#..##.#.#....22222222####..............##
#...###.#.##22##2222222##........####..##
#.###....##222##22222.........#####....##
#......2222222222222####..#......#....###
#.####...222222########..#.#..._.#...####
#.#..#....##############..#111...#.....##
#.#..+.....##############11111######...##
#.#..#.......#####....##1111111.........#
#.#..#................11111111111.......#
#.####..............111111111##+++##....#
#....................1111111.#.....#....#
###+############........111..#.....#....#
#..............+.............#..>..#....#
#..............#.............#.....#....#
#########################################
As long as the zones are sufficiently large enough to fill the thoroughfares they inhabit, and as long as the number of zones per level is random, this doesn't punish autoexplorers nor does it give players a predictable means of trap avoidance. — Wensleydale 2011-10-23 03:20

Analysis

  • Vault traps ensure that you'd be slowly rummaging through Tomb, as now.
  • No more boring trap incidents without monsters around.
  • Cleared areas are safe from traps, so no problems with stash runs.
  • No scumming against spawn traps: they occur near the monsters. T&D helps, and so does careful exploration near monsters (if you can afford to rest/wait near them). Luring does not.
  • As presented, T&D would be the fourth defensive skill (with Armour, Dodging, Skill). It would prove useful in combat, but you can completely skip it. I don't buy the argument that “higher levels of T&D are not exciting” since higher levels in the other defensive skills aren't exciting either. However, T&D has the potential to be exciting with trap planting.

minmay's radical proposal

This proposal heavily redefines the purpose of traps, but it is (relatively) short and simple.

Main points

  • Remove: Traps & Doors skill, mechanical traps (including pressure plate), secret doors. This removes trap disarming, which is frankly a pointless mechanic.
  • All traps are revealed from the start. You won't step on them unless you want to - no autoexplore problems!
  • This means calling them “traps” is probably inappropriate. “Teleport trap” should be “teleporter.”

What individual traps now do

  • Alarm traps (now simply “alarms”) can make it more difficult to get certain loot stealthily. Ossuaries, for example, use them in this capacity. Note that these are currently very weak, they need to make more noise and at least part (not going through walls) of the 0.8 noise changes should be reverted.
  • Shafts are a resource similar to an escape hatch, except they are single-use, and you can use them against monsters.
  • Teleportation traps (now simply “teleporters”) are mainly a good thing for the player; they can get them away from monsters. As has been mentioned many times before, they should have a limited number of charges.
  • Webs are a terrain feature. They make movement slower and it's not predictable exactly how slow they make it. This makes them an ideal replacement for secret doors, and in some cases mechanical traps, in many vaults (mainly ossuaries).
  • Zot traps (need a new name, like “Zot Circles” or something) are a very hazardous terrain feature that you need to prevent monsters from stepping on. This may not be interesting enough, so an alternative is to just remove them.

The new shaft effect

Shafting is a great effect, but shaft traps only work if you don't know about them. Introduce a shaft-like monster spell that sends the player a few levels down, maybe even into a different branch. Resistible with MR, of course.

Now for the most radical part of this radical proposal. I do not expect devs to like this part, but it's a part that can easily be left out while keeping the rest of the proposal. I want a shaft-like effect to replace banishment. Distinct from the other shaft effect, it should send the player to a location unrelated to their current one (this is necessary, otherwise you'd go to D:1 to unwield distortion), probably a random level out of a hardcoded set (sends you to a level between D:20 and D:27, for instance). The flavour of this is space warping around you - think of it as a teleport on a larger scale - so it fits perfectly with getting hit by or unwielding distortion.

The best part of this and my major motivation is that it makes “banishment” much less annoying. Abyss is trivial for strong characters, and strong characters will have already cleared most of the dungeon, which means it only wastes a few seconds of their time instead of ten minutes. Against weaker characters, the effect is very similar balance-wise.

Other notes

Cutting mechanical traps and secret doors will require revision of many vaults. I personally volunteer to do this. — minmay 2011-11-29 17:29

Trap propositions

This is a purposefully vague list of new trap ideas. (The last discussion got bogged down in a number mess.) Bear in mind that traps are supposed to be interesting on their own, and that avoiding them via T&D should be useful. All of the following traps have a single charge: like shafts, they disappear after use. Note that traps like portcullis are already in use via lua (check des/traps/ for inspiration).

Item destruction

  • Fire traps (Red ^)
    • Most basic version: some fire damage, burn scrolls. (In general, damage should be nominal
    • Fire cloud (has the advantage of letting players use blink).
    • Sticky flame (makes player choose scroll order when dropping).
  • Ice trap. (Blue ^)
    • Basic version: a little cold damage, destroy potions.
    • Ice cloud.
  • Magic trap: MP set to zero, wands lose charges in a “magical storm”. (Currently, wand charges are sacrosanct. The idea that wand charges can get lost in magical explosions/storms is old, and good.) The MP loss is the flavour equivalent of damage for Fire/Ice traps.

For all of the new traps, both damage (which can be nominal — it is for flavour reasons) and destruction potential should increase with depth.

“Cloud traps” could have a broad range of effects in general; miasma, poison, meph, petrify, mutation. Also see “Tactical Usage” for how to make these actually a resource. — mumra 2011-09-04 17:26

galehar: We can use the existent expose_player_to_element function which does the damage and the item destruction. It uses a strength parameter and each item has strength% chance of being destroyed. clouds have a strength of 7 and lava a strength of 14. Maybe we can randomise the dungeon level a bit (10 - d(10-N) for example) and use it for the strength of the effect. What is interesting about this function is that all items have the same chance of being destroyed. So it means the more you carry, the more items are going to get destroyed. And carrying junk items doesn't help at all.

Optional: detected Fire/Ice/Magic traps can be set off with a thrown projectile (or something more subtle if we want, e.g. needing fire dart, flame/fire wand, fire spell to trigger a Fire trap etc.). This is gimmicky and not the crucial point of this proposal. (In any case, they can be disarmed like mechanical traps. No idea if you should get something if successful.)

There are cloud traps in trunk now. The mephitic/petrify ones are great, the poison ones are okay, but the fire and ice ones feel really cheap. They don't create interesting tactical situations, they just…destroy your items. Granted, I really dislike item destruction in general, but it is especially bad here since it doesn't even feel like it's your fault that your scrolls are getting burned. — minmay 2011-09-26 02:49
In a discussion on ##crawl-dev the consensus seemed to be that cloud traps are only marginally more interesting than mechanical ones, and those with permanent effects (fire, ice, mutagenic) add problems on their own. If you see a fire drake or a fire crab, you can at least run away, these traps just destroy items without you having anything to say. This can be significantly avoided by frequently stashing potions and scrolls, as having 1 potion on your person makes you lose only 10% of what you'd lose if you had 10. This just adds tedium and frustration while hardly ever being interesting. — kilobyte 2011-09-26 02:54
There are no mutation clouds. It also appears there might be a bug which causes a turn to be skipped when clouds appear (elliptic commented on this), so actually item destruction should happen on the next turn, giving you a chance to avoid it. Another option would be to introduce a delay of 1 or 2 turns after the trap is triggered before the cloud explodes. — mumra 2011-09-26 08:17

Ailments

  • Hunger trap; lose x satiation (but only down to Near Starving).
  • Sickness trap; you lose maxHP like from rotting (but no Rot status). Protection from sickness prevents.
  • Cloud of miasma with short duration.
  • Forgetfulness trap; you temporarily lose skill levels. These regenerate by exercising them - it trains normally, and the temporary loss is regained with an appropriate factor (like ten times faster than training). Clarity prevents.
  • Acid trap; some acid damage, but more importantly corrodes wielded weapon and worn armour.
  • Curse trap; curses worn armour and wielded weapon. Possibly shouldn't be abusable by Ashenzari worshippers; OTOH, the trap should have a single charge, so perhaps discovering one simply becomes a resource.
  • Magical bear trap; when you activate it, you take a little damage and can't move from that spot for a few turns. Magical, because it also prevents teleporting/blinking out. — nicolae 2011-10-02 02:40
    • This has similar problems like the current, mechanical traps: it means nothing in the absence of monsters. Webs may work similarly, but they are defined by having monsters nearby! — dpeg 2011-10-02 16:10
      • Ah, nuts. Good point. Maybe once activated, it spawns a hunter-themed monster just out of LoS, who comes to see what he's trapped, combining a summons and immobilization (and a little flavor to boot). “The bear trap snaps on your foot! You hear a nearby voice exclaim, 'Ah, caught somethin' finally!'” (New unique, who leaves a level full of traps and only shows up by teleporting to the first one you activate?) — nicolae 2011-10-03 15:46
These all seem to create interesting situations that you have to work around (without the danger of just killing you outright, and without being able to simply rest it off) - so should be good.
Miasma - more clouds - see previous section.
Acid - could be quite harsh, especially with enchant scrolls being relatively rare. Maybe acid could be a new cloud type; and ensure that you have at least 1 turn to take action (i.e. blink, or put on rCorr) before anything bad happens.
Curses - Ashenzari could shield you from the curse, just like death curses. — mumra 2011-09-04 17:34

Summon and global traps

  • Summon traps: you trigger them, they summon stuff (like with ordinary summons, no xp/piety/corpses; unlike most summons, they could be very long-lived, even eternal until dispatched). There are variants:
    • just summon stuff around the player
    • spawn a certain type of monster around the map (perhaps without message!), e.g. jellies, boggarts, etc.
    • summon a large number of monsters just beyond the players LOS
The spider basket trap is a fun example of this, what would be great is a whole range of different types of things that can be summoned, and tactical situations in which it can arise. I wrote a sample vault file that summons shadow creatures in a bigger area of LOS, and it's easy to make the summons depth and level appropriate by adding any number of vaults with different DEPTH: parameters. The script might need some revision but it's at: http://pastebin.com/LTg8CAmDmumra 2011-09-04 17:34
  • make the level -cTele (danger: players might be tempted to lure monsters to another level)
  • slow movement on the level (forever)
  • being watched: awake monsters know where you are
These are perhaps extreme; and being watched isn't really any different than a more powerful alarm trap. — mumra 2011-09-04 17:34

Elemental Traps

mumra:

From an idea by wensleydale on IRC. It's similar to a summons trap, but themed around spawning elemental monsters relevant to the local environment (and depth; slightly OOD of course). Two ways this could work: either analyse local tiles and based the spawns on that, or use hand-crafted vaults themed around a particular element. Ideas include:

  • “The walls come alive!” - some nearby wall tiles turn into rock trolls (rock wall), stone golems / giants (stone wall), iron troll / golem / elemental (metal wall), crystal golem (crystal walls)
  • “A form rises out of the earth!” - monsters spawn out of the ground; earth elementals / clay golems (perhaps ground could liquefy)
  • “Something emerges from the liquid!” - water elementals, fire elementals
  • “The trees are walking!” - wood golems
  • “Shapes coalesce within the clouds!” - combined with a pre-existing cloud generator; fire elementals / vortices / orbs, water elementals (from steam); ice beasts / devils / fiends / statues; air elementals can always appear out of nothing
  • New monsters and cloud types could be considered (e.g. electricity clouds → electric golems)
  • Similar themes - granite statues turning into actual statues; floor weapons become dancing ones

I started coding some LUA for such trap vaults; might need a wide range of themes and layouts to prevent them being hugely spoilery.

Old traps

  • Teleportation: the randomly generated traps should come with a small, random number of charges (think 1-3), to prevent abuse. We will need the unlimited (current) version for vaults, so it should be kept.
  • Alarm traps: the idea is great but the performance seems to be underwhelming. Would it suffice to increase some number?

Both sound good to me, and easily doable; teleport cap can be implemented as ammo when random traps are created. — mumra 2011-09-04 17:34

Boulders and other projectiles

mumra:

  • With the Rolling Boulder Beetle patch, I'm including various pressure plate trap vaults that roll boulders at you, with limited escape options
  • Additionally, it's possible in LUA to spawn an Orb of Destruction and direct its vx/vy at the player; this could also make an avoidable, but fun, trap. I've got a couple of vault ideas that will use it, but I think it's worth knowing for other map and trap-makers :)

I mocked up an example IOOD trap to show how it's done; not suitable to be used in the game as-is, but it shows how to place an orb at A, targetted at B: http://pastebin.com/P6m10bQF

Traps versus allies

One area we may want to explore is the interaction between allies and traps. Summoners, for example, are a bit binary: they find many fights trivial, and some quite hard. Balance could be better. I think more attention should be paid to how new game elements will affect summoners. Traps are just one example. Characters with allies might be more interested in dealing with traps effectively, and this can be expanded.

  • Shaft, Teleportation, Zot (banish) present interesting challenges for characters with permanent allies. Less for summoners, although they might catch them out of MP.
  • Zot traps in general are dangerous even for summoners, because every activation has 1/5 (?) chance to affect player if it happens in his view. Sometimes a rampaging horde of allies is a bad thing.
  • A trap making allies temporarily disloyal. (b0rsuk suggests that intelligent monsters use wand of enslavement for this purpose.)

Hidden locations

A much more vague idea: some items could be hidden and only detected with T&D skill. Since we don't want players to re-visit all areas, this idea works best for portal vaults and Pan (but there it is interesting). Best to only have a single attempt at finding the loot — we don't want players to meticulously investigage every nook and cranny in a cleared portal vault.

The same could apply to hidden devices, which could turn off all traps on a level, or find all secret doors etc. (this idea is more fancy and has less appeal than hidden loot).

Trap creation

This is an attempt to make T&D more useful for players spending xp into it, by giving it an active use. Before going in any details, the basic ideas are:

  • Traps use valuable components (e.g. charged wands, not axes or darts). Wands are good because many of them are already destructive, we can use wand type and charges as parameters for the trap effect, and they allow to make use of both T&D and Evocations for trap-planting. (We want to use at least moderately useful consumables as components so that there are choices how to use them.)
  • Traps should be used for special tasks (killing uniques, branch ends), not for everyday dungeon duties. This is why the process of setting up a trap can be slightly elaborate — you won't be doing this too often.
  • We shouldn't even try for symmetry: player-made traps are vastly destructive affairs, unlike all the traps the dungeon throws at you.
  • For a first attempt at numberical detail, please see the Sourceforge link.
I'd be against making wands for traps just cause it feels weird, and doesn't make sense since then why not use rods. Why not simply code a new device just for making a trap? A new class could even start with one or two of 'em. — greepish 2011-12-06 15:15

Tactical Usage

A new idea; being able to detect and use traps tactically could add new value to the Traps & Doors skill, making traps potentially an interesting and valuable resource, rather than a one-off hazard to just avoid or disarm when detected.

The possible mechanics and scenarios I'm thinking about are:

  • Traps can be set off a) when standing on the tile, b) from an adjacent tile, or c) from distance with a dart or stone (also requiring good Throwing skill)
  • For ordinary mechanical traps, this could damage a monster on the tile (perhaps awarding you the kill and XP) - might only be worth it when the damage is greater than just meleeing them, or pelting them with a stone or dart
  • For some of the new traps this would be far more useful; triggering clouds, even when standing on the tile (if you have appropriate resistances); setting off boulders/IOODs and getting enemies in the way of them; maybe summoned monsters could have a chance of being friendly with high T&D; in all cases you should earn XP for (normal, non-summoned) monsters you kill by (ab)using traps
  • Leading on from this, high T&D skill could allow you to detect the *nature* of pressure plate traps - this would require some LUA changes so an extra string can be passed in describing the trap
  • High T&D skill could also detect how much ammo was left in a trap; perhaps marginally useful, but when using traps as weapons it might allow you to plan a little …
  • T&D skill could also influence how effectively the trap is triggered. More damage for mechanical traps, bigger clouds for cloud traps, more/friendlier summons, etc.

mumra 2011-09-04 17:15

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