Tuesday 10 August 2010

Designing a Magic System Redux - Part Two (Status Effects continued)

You should read part one of this article, and are strongly encouraged to read the original Designing a Magic System series of articles if you have not already done so.

There is an asymmetry in the design of status effects in Angband: they differ (sometimes significantly) in implementation between the player and monsters. But I've aspired in Unangband to reduce the asymmetry between the two where possible so I'll begin discussing the impact status effects they have on the player and briefly note into the differences between the player and the monster at the end of the article.

There is also a difference between the original Angband, and Unangband implementation of status effects, where Unangband has more possible states, but compensates by weakening the impact of the original Angband effects. The primary approach I've taken is to make it harder to add additional time to a status effect once the player is already affected by it - to avoid continuous locks. I've also modified the effect where noted below with the intention of making it easier for the player to continue to act when partially impaired without requiring they immediately reach for a reset of the effect.

Blindness was the example I looked at in the first part of this article: a player who is blind has a significant penalty to hit when attacking and cannot read scrolls or cast spells - presumably being unable to read the words from the spell book. In addition, the player stops getting screen updates - so that they are not able to see the current location of enemies or changes in surrounding terrain. My intention in Unangband is to weaken the blindness effect slightly, so that you can cast a spell once, from memory, while you are blind, before forgetting it. This is a shout out to my AD&D 2nd edition roots, as well as a way of allowing the player to sneak around in the dark and still cast spells.

Amnesia in Angband has been changed to a timed effect, based on Unangband's implementation, so that you suffer a penalty to your chance to cast spells. Unangband also prevents you from activating artifacts and other items - it makes you temporarily forget you have identified them - and when blind, will stop you from casting spells at all. (At the moment Unangband stops you from casting at all while merely amnesiac, but I'm changing to closer match Angband in the next version).

Confusion in Angband prevents you from spell casting, as well as causing you to move and shoot in a random direction instead of the intended direction. I weakened this effect in Unangband so that you can cast spells while confused - because the random target selection effect when combined with the ability to hurt yourself with spells makes for an interesting risk vs. reward trade off - and also made confusion only having a percentage chance of taking effect which increases as you become more confused.

Fear prevents you from fighting monsters in melee - you refuse to attack anything that you bump into. This is meant to encourage the player to flee, but it instead merely forces you to switch to missile weapons or spells, which there is no penalty to use even at point blank range. To compensate for this, I'm adding an additional terror effect, which acts as an 'overflow' to fear. Once you become sufficiently afraid, any fear will overflow into the terror status. While you are terrified, you cannot use any ability which requires aiming - including spells, missile or thrown weapons. You are still able to use other abilities, amongst them the various teleport effects you should be considering to escape with.

I've taken advantage of multiple meanings, to provide an alternative overflow from fear: that of petrification. Petrification status prevents you from moving (although you may teleport still), and has no other effect - although most direct petrification attacks are highly damaging as well. It is possible in Unangband to become petrified with fear, in the same way that terror overflows - and the two different types of overflow are exclusive: you'll either become terrified or petrified if you are made highly afraid, not both.

Paralyzation is the most uninteresting status effect: you simply cannot do anything while paralyzed, and so it is incredibly hard to balance and puts the player at the highest risk of getting a lock. Unangband has a second, more interesting variation: stasis - which paralyzes you, but also makes you invulnerable to damage, which is a side effect of time attacks. Stun deserves mention here because it incrementally penalizes you to the point of knocking you out, an identical result as paralyzation, but the initial penalty is very slight. Both paralyzation and stun are less interesting than the status effects I've already mentioned, because you either perfectly resistant or are in incredible danger should you encounter a monster (or worse group of monsters) which inflict this effect, with very little margin in between. To mitigate paralyzation, I use the slow effect as an intermediate step, with you being slowed before you are paralyzed the majority of the time.

Using the above combination of effects, you can chart the impact on the player's abilities as follows:
You might be tempted to add, for example, a Nausea effect to the above chart, which prevents you from using potions. But I'd discourage this: potions are best kept as the get out clause reset for any effect. It is still possible to partially incapacitate yourself through bloating by stuffing yourself with food and drink, for which a potion of Salt Water is a useful antidote.

You'll also notice Daze in the chart, which I haven't provided an explanation for yet. Daze will be new to Unangband in the next release: it prevents the caster from casting spells on himself and is the direct inverse of Terror, but for only spell casting and (perhaps) magical devices. Daze is interesting because it forces you to use spell attacks which are hampered, or my preferred terminology, made more interesting by blindness and confusion. To complement this, both Confusion and Blindness overflow into Daze, and there is no direct way of a player being dazed by an attack.

Of the effects in the above chart, only petrification, fear, blindness and amnesia of themselves totally incapacitate some ability of the player. The remainder only incapacitate in combination, or as a result of another status effect being repeatedly applied to the point where it 'overflows' into a more dangerous status (Terror and Daze cannot be directly applied to the player). The idea here is the player should get some opportunity to use a reset to avoid incapacitation, with a large margin of error before the more dangerous state occurs.

There are in fact 32 status effects which can negatively effect you in Unangband: of those I've not mentioned, the remainder are either debuffs (stat modifiers), change the rules monsters use to track you (aggravation, stench) or damage over time effects (poison, cuts) and so don't need result in the complete incapacitation which causes a lock. There a Soaked effect which prevents you from lighting fires or reloading firearms, and a Berserk effect which allows you to voluntarily give up missile and magic attacks in return for improved melee, healing and immunity to fear but both of these will have minor impact compared to those I've discussed in depth.

There are two exceptions: Sleep and Hallucination.

Sleep is one of those spells from AD&D which I cast into the same problematic category as Magic Missile. It was a 1st level spell which either fails or immediately and completely incapacitates with no in between. Sure, you can increase the level casting requirements and have the victim wake when attacked instead of being able to deliver a coup-de-gras, but the ability to completely disable an opponent and escape means the spell has to be made effectively useless against any opponent you'd want to use it against. Sleep works great in a role playing game which is strong on the capture and interrogate dynamic: not so for computer games.

Angband sidesteps Sleep effects against the player completely in favour of paralyzation, which is less a solution and more a tactic acknowledgment of the scope of the problem. Unangband separates them: and gives the player a cool down before falling asleep, which you can cleverly use to damage yourself to stay awake. Should you keep damaging yourself for the duration of the sleep spell, you'll avoid the effect completely.

Hallucination is a fun trick with ASCII graphics, but has little functional difference, and a lot of overlap with the confusion effect. Unangband already has enough restrictions on spell casting to make it worthwhile having hallucination stop spell use as well. But the Nightmare on Elm St of sleep started to get me thinking about what hallucination should do.

Sorcerers in Unangband don't have the range of options that the other major spell casting classes do. I've tried to remedy this by letting them make magical traps, but this both lessens the utility of actual trap setting, and requires enough horrendous hackery that I'm forced to reconsider. Sorcerers can shape change, and charm, and like druids have a minor in summoning spells, but I've come to realize that status effects should be the sorcerer's forte. But blinding and confusing and dazing monsters leaves two problems for me to wrestle with: firstly ensuring that the time required to get a lock on a monster is approximately the same as killing it, and making clear the victory conditions for doing so.

I will be reusing the surrender code to allow monsters to gracefully give up to the sorcerer: but it is more difficult to decide when this should occur. With hit points, we have a clear definition: when the monster is near death. With status effects, I have to define more clearly how to get a lock.

Take the following chart:

This is the status effects I've described previously, excluding effects that disable all a monster's abilities, with arrows used to indicate where one status effect overflows to another, and where abilities accumulate together to provide a 'higher level' result. I've added one additional overflow: confusion also can also overflow to hallucination - which will be important later.

If a monster is both frightened and petrified, it is considered in a melee attack lock. It cannot provide any kind of melee threat to the player, and if it is only capable of melee, it provides no further threat to the player until it recovers from either effect. Similarly, terror provides a ranged attack lock by itself, where ranged attacks are either shooting or breath weapons, and either amnesia and blindness, or terror and dazed effects provide a spell casting lock. A monster will surrender if it has all its abilities (melee, ranged, spell casting) locked for sufficient time and it has no allies in line of sight which are also not incapacitated. If a monster doesn't have one set of abilities it is is easier to lock.

In this way, aiming for a status lock is a broad attack in that you have to apply multiple different effects to a single monster for it to be defeated, whereas damaging attacks are deep in that once you find the vulnerability, you repeatedly exploit it with the same attack.

Also note that if the monster is immune to a particular status effect it is also harder to get into a lock: for instance monsters which are immune to fear cannot be melee or ranged locked unless it is possible to directly apply petrification or terror. Ideally there should be multiple paths to achieve each lock, so that a monster which is immune to a single type of status lock can still be affected by applying another combination of status effects. I am tempted to make the hallucination effect also prevent ranged attacks - another alternative would be to make confusion plus blindness effectively act as a ranged attack lock, because a blind and confused monster is unlikely to be able to use any ranged attack effectively.

But even if I make hallucination prevent ranged attacks, it still feels like the unwanted step child of status effects. Luckily, I've come up with a fevered dream of a solution that should give Sorcerer's yet another way of attacking monsters with status effects.

What is missing from Unangband is the ability to create illusions - something a Sorcerer class should excel at. There's a number of ways to implement illusions: you can have monsters which disappear when attacked, mirror images of the Sorcerer which disappear when attacked... all in all, a little ineffectual.

But what if you allowed illusions to cause real damage while the target was affected by particular status effects: I'm thinking specifically of while sleeping. That way you could have illusions interact with real monster resistances so that if you tried to burn a monster with illusory fire which is normally immune to that effect, it notices and wakes up, whereas you could damage it while asleep and have it remain asleep if it succumbs to the illusion. The incentive here is for the Sorcerer to attack monsters as they asleep, but have to periodically force them back to sleep as they are awoken by the illusory effects you cast at them. Pure damage could be represented by the Sorcerer's existing mental attack abilities, which would cause double damage to sleeping monsters whereas the various illusory elemental attacks would require the illusionist play by the same rules as regular spell casters.

And in this scheme, the hallucinating status effect would similarly allow you to affect monsters with illusions while they are awake. The advantage to hallucination is the sleep effect has a time delay before the monster succumbs, whereas hallucinations take effect instantly.

This is followed by part three which looks at magic items in more detail.


kaypy said...

An effective hallucination based effect would be something like NetHack's conflict: critters could either start explicitly fighting each other or at least have a tendency to start fighting if they bump into each other/shoot 'past' each other etc.

This would of course only really apply to the player if they have summons or allies and could only really remove any friendly fire protections (hence suggesting not making the enemies outright start fighting either)

To some degree what you need is a way to keep track of where a given creature thinks an enemy *might* be, so they can lose track of that information over time or due to events (like being attacked by that *other* unidentified hallucination)

RedFoxOne said...

I found this to be a really good article and something that I will look to during my design phase for status effects.

Andrew Doull said...

Kris: That's an excellent suggestion.

The big problem with hallucination creating conflict is an AI issue to do with asymmetry of intent. If monster A is hallucinating, and attacking monster B, which would normally be friendly to it, what should monster B do?

Should it fight back at full strength? Should it try to take down monster a in a non-lethal fashion, or try to heal it? Should it pre-emptively attack monster A, if it sees monster a getting affected by a hallucination attack, but has not yet attacked any allies?

These decisions are nontrivial, and particularly for player allies, it is not necessarily clear what the right thing to do is.

VRBones said...

There's an interesting line between trying to avoid a lock for the player while simultaneously allowing easy access to locks against monsters within the same system. My guess that balancing enemy sorcerors would be the next logical step in this tit-for-tat battle.

Did I miss something or was the resolution to the binary nature of sleep to just allow a time delay for the effect to occur? It would seem that adding bonuses to attacking slept opponents for the sorceror would exacerbate this all-or-nothing aspect.

I'm also not sure on what you mean by continually hurting yourself to stay awake (Can't remember if this was implemented last time I played, sorry). Wouldn't only 1 turn of hurting yourself remove the sleep effect?

Even if you have to continually hurt yourself, is that not a 'soft' lock anyway? The casting of a sleep forces a specific response or fall into a 'hard' lock. If your opponent kept casting sleep, you would effectively be in a locked state. I guess you could choose to teleport or something and suffer the sleep lock in a potentially safer position.

As to the hallucination, it might be an interesting rewrite of the hallucination screen code to have the initial state diverge into multiple possible states displayed at once (seeing double,etc), with other phantasms coming in and out as well.

For moster conflict, I've usually been pretty happy with "damage received" being a trigger for enemy status. There may be an exception if their teammates have the ability to cure hallucination (you would assume this would also come with the ability to recognise someone under hallucination). Leaving the states fairly simple helps the player have some tactical certainty about the use of a spell/effect.

Kinda just thinking out loud, take it with a grain of salt ...

kaypy said...

I never claimed the implementation of any of this would be easy 8-) It just seemed to most true-to-myth combat mode for the class...

Oh, another open question: Should you, given a character based on locking opponents, be able to lock the final boss? On the one hand, it seems rather anticlimactic, but the alternative is to make a character type, in the end, a user of 'Useless useful spells'

Are there any story examples where the 'end boss' has been taken out via breaking their mind? (As opposed to the zillion and one cases where the villain has tried it on the hero). I can think of one or two 'almost' examples, but it still seems to come down to a physical brawl in the end...

Andrew Doull said...

Kris: I forgot to add the 'linked to TV tropes' status effect.

That's a total lock right there.

The LoTR mythology certainly supports putting Morgoth to sleep.

VRBones said...

Superman 2 villians placed in stasis on Kal-el?
(looks like the stun lock wasn't infinite though ..)

Andrew Doull said...

VRBones: You can hurt yourself to stay awake. This increases the time delay before falling asleep. IIRC it is 5 turns, so you can keep awake permanently by hurting yourself every 4 turns...