Auto-dynamic difficulty

There is a zone beyond that which is known to game designers. It is a place as vast as space and as timeless as infinity. It is the middle ground between boredom and frustration, between easy and hard, and it lies between the tips of our fingers, and the sparks within our CPUs. This is the dimension of pleasure. It is an area which we call... THE FUN ZONE.

(Forgive me, Rod!)

Okay, that out of the way, I'm going to start off with an actual, complete email I sent to the project leader of Max Payne a few months before the initial release of that game in mid-2001, almost three years ago:

From: "Scott Miller"
To: "....... ......."
Sent: Thursday, April 12, 2001 1:54 PM
Subject: Re: Max Payne Build 125

Here's the reasoning behind not having an easy skill level: We do not want players to finish the game and not have a satisfying feeling of accomplishment. Too many players will pick the easy mode just to get through the game, and end up finishing and think, "Well, that was nothin'! Where were the enemies!? Where's the challenge?!" In other words, if we give players a chance to shoot their own foot, some will.

Diablo 2 obviously didn't suffer from not having a skill level choice -- it's one of the three best selling games ever, with 2M and still selling.

Also, my view is that as developers, it should be *our job* to properly play balance the game, not the player's choice. In other words, skill levels are an easy way out for developers too lazy or incompetent to properly play balance their own games. (Okay, a bit harsh, but I'm saying this as someone who used to be a strong proponent of skill levels, too, so I was part of that incompetent developer group! *grin*)

Finally, a skill level screen is just another screen getting in the way of enjoying the game itself, like those boring as hell logo screens that I hope to g.o.d. we can get rid of in all future games we release!

Anyway, the perfect game will adjust its difficulty based on the player's personal ability. This was done in arcade games going back to Atari's Xevious in 1982. It should be really easy to do: Simply have a few variables that rate the player's ability, and the player's rating (completely internal to the game) determines the damage that both the player's weapon delivers, and the enemies' weapons deliver against the player. You do not want to adjust the health benefit of pain killers because that's something the player might notice being adjusted as the game goes along because it's represented by a visible bar.

A few ideas for variables that determine the damage ratings of weapons might include:

o Max's average health (i.e. if it averages around 25%, then the weapon power variables need to be adjusted to favor Max slightly, but if Max's health averages 80% or higher, then up the difficulty).

o Kills made per level, vs number of possible kills per level. A good player will leave few left standing, if any at all.

o Number of times Max dies per level -- this is a good indication of how good the player is.

o Note: I wouldn't keep track of shots fired or number of saved games--those can be misleading either way.

Finally, never make a change during a level, only between levels.

At the end of the game, via a cheat code, you could plot a graph of the ups and downs as the player played the game, which would be a very interesting graph to compare with other players!

Scott Miller
3D Realms Entertainment
www.3DRealms.com

As can be gathered in this email, it's my opinion that games should only rarely allow players to set their own difficulty level. Afterall, it should be the designer's job is to insure the proper play experience, not the player's. The idea behind auto-dynamic difficulty (ADD) is to keep the player in the sweet spot, where the game remains challenging, but never impossible. A perfect game experience is one that constantly tests the player's skill, without being so hard they want to give up. Completing such a game gives a player an elated feeling of accomplishment, because they know they passed a tough test of their ability.

One of the key challenges developers must overcome in broadening the appeal of our games is making our games less hardcore in nature. We need to improve in many areas, like interface, content, and adding emotional involvement for story-based games. ADD should become one of our best tactics to help us achieve this important goal.

One of the most common ways games sabotage their potential to appeal to larger numbers of players is by being too difficult (or too easy, but that's much less common). Practically everyone designing games nowadays is a hardcore player with elite skills. It's therefore easy for game designers to misjudge the difficulty of their own games, making them too hard for average or new players.

Sequels, especially, are a breeding ground for ramped up game difficulty. The natural tendency with sequels is to add more features, leading to more controls. And higher game difficulty. Also, with sequels designers naturally assume that players have all the skills learned from the previous game, and so the challenges are made tougher for new installments. Not exactly an inviting situation for anyone but the hardcore gamer.

ADD provides the near-perfect solution for most problems dealing with game difficulty. At least if implemented well, but that's the case with any facet of design. There are two primary issues with implementing ADD:

[1] The first issue when implementing ADD is to make it invisible to players. It should not be obvious when the game is self-adjusting its difficulty level, as this can hurt the game's immersion.

[2] The other issue is to make it so that's it's hard for player's to manipulate the system, taking advantage of it. For example, a player might play very poorly for the level leading up to the boss, just to make the boss a breeze to beat. While clever players will always be able to manipulate games with ADD, there are ways to make manipulation more trouble than it's worth. And, the bottom-line is that players who do this are only cheating themselves, so perhaps this is not too great of an issue.

One last point that developers should consider: If a player completes your game, they are much more likely to buzz about, spreading the word that it was a great game. We all love to brag about feats of accomplishment, and beating a game, for a gamer, is near the top of the list. A game with a well implemented ADD system is more likely to allow players of wide ranging abilities to complete your game.

I think Max Payne benefited greatly from its implementation of ADD. And I think this should become a standard feature for most games. At least, if broadening our customer base is of any concern.

Comments

[Collin van Ginkel]

Interesting article I must say!

I'm sure you look at things from a console/PC perspective, but we've had a similar experience while balancing Toki Tori ( http://www.tokitori.com ) for Game Boy Color. It's a pretty simple-looking game but it's one of the hardest games around on GBC to complete.

Because Toki Tori levels are tightly designed puzzles for the player to complete we couldn't really adjust any game settings dynamically. We knew we were creating a tough game, so we didn't make it mandatory to complete all the levels in the game. You only have to complete 40 of the 60 levels in the game to see the ending, and when players actually finish all the levels they are rewarded with a special gift.

If even 1% of all the buyers completed all the levels I'd be surprised. But still, the reactions we get from that 1% are totally worth the extra effort we put into it.

[Brad Renfro]

I am all for ADD, and even other forms of intelligent adapting dynamic gameplay systems. I thought it worked really well in both Max Paynes. But here are a few more issues I came up with.
- Sometimes, I feel like breezing through a game just to see its story. Then I want to manually pick the easiest setting.
- Sometimes, I feel like I am a badass because I specifically choose to play games on the hardest difficulty. I want the choice and honor of picking nightmare difficulty. The elite difficulty modes in the Max Paynes and Diablos worked well but had to be unlocked.
- Even though it's dynamic, the ADD designer still has to concretely determine what constitutes easy difficulty and hard difficulty. It still involves setting down tweaked variables. If a designer would improperly balance a non-ADD game, what guarantees that this designer would properly balance an ADD game? Even worse, if the balance of an ADD game fails, the player is stuck in this unbalanced game with no difficulty choice.
- ADD is a system that needs as much tweaking as normal difficulty level tweaking, if not more. In fact, it requires significant extra code and testing. The normal reasons that cause developers to ship unbalanced/unplaytested games apply to an ADD implementation as well (lack of time, lack of manpower and budget, poor design principles). If anything, the extra work involved means that games could be even worse if poor ADD implementations become the norm.

I guess even with ADD, it still comes down to design talent and time/budget to allow design polish.

[JP]

"Number of times Max dies per level -- this is a good indication of how good the player is."

Actually, in the case of Max Payne, it's not really. The game frequently kills / damages the player with no recourse because the player has no information on what's going to be in the next room and the weapons are frequently lethal enough to whittle a player down from full or near-full health to zero in a short time. Ask anyone who played the game and they will all say they had to use quicksave to scout rooms at least a few times. Jump through door (because of the way the bullet time economy works there is never a reason not to use it), get blasted by the customary two-guys-with-uzi + one-guy-with-shotgun, quickload, do the same thing but ace the room now that you know how to handle the situation. This is called Teaching with Death, and anyone who does it needs to go back to game design school. Making your ADD algorithm aware of how many times the player has died is throwing good effort after bad.

Also, the citation of Diablo2 at the beginning of the argument - a completely different game in a rather unrelated genre that just happens to have sold really well, a game that *does* actually offer a skill level choice once you beat the game once and has no ADD - is pretty much useless and goes to show how rudderless your game design practices are if sales are your only quality metric.

Also, what exactly does it mean for something to be "auto-dynamic"?

[Jeff Mackintosh]

If a designer would improperly balance a non-ADD game, what guarantees that this designer would properly balance an ADD game?
-----
I think Brad brings up an excellent point. While I think an ADD game is the right choice (I think it makes a game better in virtually every way), I also think that a weak designer using difficulty levels as a crutch will do a poor job designing an ADD game. If they need the crutch to make a good game, that almost ensures they will screw up a game without the benefit of that crutch.

Of course, in a perfect world, all game designers would be good at their job and not require crutches, but we know we don't live in that perfect world.

Well, not all of us at any rate. :)

Anyhow, that was another excellent and thought-provocking post. Keep up the great work.

[Gestalt]

Dynamic difficulty settings are a nice idea in theory, but as has been pointed out already - 1) players don't always want the game to be challenging but not quite impossible, and 2) Max Payne isn't a great example because its dynamic difficulty settings didn't always work very well.

Personally I found some of the later stages of Max Payne virtually impossible. I'm guessing this was because you didn't use frequency of saving and reloading as a factor in the balance equation. The harder the game got, the more often I would quick save and quick load, often not waiting for Max to actually die but simply reloading if I was badly injured in a fight and there weren't any painkillers immediately to hand. Judging from your e-mail above, this might actually have made the game harder instead of easier! Which would make me reload more often, which would make the game even harder, which... ;)

Until games can accurately judge how tough I'm finding the game and whether I'm having fun, dynamic difficulty systems shouldn't adjust the difficulty too drastically, or they might make it completely unplayable. And they should start from a base easy / medium / hard difficulty setting that players can pick manually because no game, however clever the coding behind it, can tell how hard I *want* the game to be.

[Brian Gladman]

I agree with the earlier posters, in that MP (particularly MP2) was an exercise in QuickLoad/QuickSaving, more than anything else. Enjoyable nonetheless, but still required a QuickSave after every battle. This is not good design, IMO.

The best example of "ADD" I can think of is Sly Cooper. This is a game I could play with my 4 year old son, and it would adjust accordingly, being more generous with gold coins/extra lives when he was playing (and dying!), and more stringent with the goods when I was breezing through it.

[Scott Miller]

All: I'm not saying that Max Payne had a perfect ADD system in place, because I know it didn't. But, if more developers started using ADD, we'd see gradual improvement over time. Most games do not use ADD, especially shooters, so Max was on the leading edge within its game category, and leaders seldom get everything right.

The key point is that ADD is to the benefit of players, and therefore the industry. It allows games to better cope with a wider range of player abilities. But in its own it will not correct overly difficult level design, tough jumping puzzles, and so on. Level designers must still do their jobs well for ADD to shine.

Re: Diablo, true it didn't have ADD, but I thought it made for a good example, due to its success, of a game that didn't allow players to select a difficulty level. ADD caries this one step further.

Also, the technique we used in Max Payne allows players to select a harder difficulty level AFTER they've finished the game, as at this point it doesn't matter, and players often desire a harder challenge if they replay the game.

[Benjamin Graner]

Interesting read, and I can see ADD being useful in balancing the needs of hardcore players while keeping the game accessible to the newbies. I just want to point out my biggest problem with ADD and why I feel it should be used with a bit of caution.

In a sense, ADD basically says to the gamer 'you are going to beat this game no matter what'. If the game adjusts it's level of difficulty so that the game is essentially always beatable by that player, where is the satisfaction in finishing?

It's like the game of poker I played last night with my friends. At the end of the night I was down $5 and my friend was sitting on a huge pot. I guess we all looked glum, because he tried to give back the money he'd rightfully won. None of us accepted. If we let him, what was the point of playing at all? Poker is exciting because you have something to lose. When you win, there is satisfaction because you might not have been so lucky, and you were willing to put something on the line for a chance to play & win.

ADD, if it's opaque to the player is the same as my friend giving back our money...it softens the blow of defeat, but also takes away from the satisfaction of winning. Why play a game you know you're going to beat? Where is the fun in that?

Personally, I'm biased toward the Final Fantasy solution: Make intermediate enemies plentiful and easy to beat, and ramp up the difficulty for boss's and out of the beaten path areas.

So you want that BFG? You're going to have to go through the uber-mutant which is guarding it.

I guess attention deficit disorder is great if you can tell a gamer is really having a hard time and needs some help, otherwise I would personally throw lots of easy enemies at a player with one or two major obstacles.

[Scott Miller]

-- "In a sense, ADD basically says to the gamer 'you are going to beat this game no matter what'."

Great point, Ben, but is this really so bad. As long as the road is difficult, I *want* people to finish the games I help make. And even with a perfectly tuned ADD system, it's still up to the player to beat the game -- it doesn't become a walk-thru.

[Nathan Peterson]

I'm also assuming that Scott ment there would be a 'floor' to the difficulty level, so the game doesnt become so easy, that anyone who plays it the first time, can simply walk thru it?

I would be a fan of more hybrid approach, where ADD could change the basics of gameplay (such as thuglike enemies behavior) and then for intermediate bosses or level bosses, to have a set difficulty, or at the least, a much smaller scale ADD difficulty scale depending on the players performance in that level.

That way, obsticals are still obsticals, and a player has to really work to move foreward, and to advance their skills in the game.

hence making the ADD function more later, when the player starts to use more skill against tougher enemies, or bosses.

just a thought, on how ADD could work, and still provide a satisfying 'completion' feeling.

-nathan

[Factory]

Hmm another way of doing ADD is done by roguelikes, which is to put a series of gradually increasing in difficulty levels, and let the player go down as fast as they like. The player sets their own difficulty level by adjusting the number of levels they down to. The incentive to go down is that you get more loot the further down you go. This system has the problem that one can easily go down too fast, and get yourself in trouble, and also that the speed at which a character descends is not generally linear, some levels can be descended faster than others.
Diablo has a similar system, althought the end of level bosses tend to act as obsticles that must be passed, while a roguelike like Angband will not be as strict. 'Boss' monsters will generally hang around a set of levels and be an annoyance to the player. (if a Boss is too hard, it's generally easy to flee past it)

[Jim Vessella]

I really love the comment Ben made about side quests. From my experience, most people who play RPGs will first play to beat the game and see the story. Afterwards they're go through and try to collect all the items, beat all the monsters, and explore every inch of land until its painted with your dominating presence.

While there is no actual difficulty setting at the beginning of the game, the player can choose their difficulty by the actions they make. Some games now give you a "percentage completion" meter that reflects how much stuff you've done in the game. A great example is Metroid Prime, where at the end the player is rewarded with a different cinematic depending on how much they completed. Not only does this provide a total esteem boost when you complete the game with say 90%, but it gives you that extra incentive to go back and complete 95 or 100% if you're super hardcore.

[Cebrian]

ADD introduces an element of variability at the rules that the player can easily identify as cheating. Players usually want a "fair game", one with a fixed set of rules they can feel and understand: a bullet to the head will kill, three bullets will surely kill this particular enemy, and so on. It also hurts the immersion and the solidity of the game world. A main premise of the ADD is that the player won't know it exists. As a game mechanic, penalizes good play while rewarding bad players. It just doesn't sound right. Maybe it can work, but I'm unconvinced.

[Gestalt]

Cebrian - "ADD introduces an element of variability at the rules that the player can easily identify as cheating"

Good point. Also, adjusting the damage weapons cause is a pretty blunt way of adjusting the difficulty. Why is it that most games just throw more enemies at the player, make their weapons cause more damage or give them god-like aiming on higher difficulty settings, rather than (say) adjusting the way the AI behaves? I can see that the AI programmers might want players to always see their creations at their best, but that's no fun if they keep killing you! Wouldn't it be cool if enemies on higher difficulty levels made more use of cover and were more coordinated with each other, rather than just having bigger guns or more reinforcements?

[wormstrangler]

"Wouldn't it be cool if enemies on higher difficulty levels made more use of cover and were more coordinated with each other, rather than just having bigger guns or more reinforcements?"

Would you like to pay for the extra coding time? :P

It just seems like a big hassle but one which would have good benefits for the player.

I hate how AI on a high difficulty is just given an accuracy of 99%.

So these types of implementations all comes down to time and the AI coders experience. AI programming has been lagging behind for a while. Maybe a 3rd party should start making AI geared towards one or two types of genres (FPS generally) and then license their technology out, like physics and even engines in general.

I'd like to be a start up in that industry, but it ain't going to happen, for me.

[Roger Taylor]

You say that skill levels are a lazy and easy way out of properly play balancing, that players should play the experience that the designer provides and imply that ADD is a way to properly play balance a game. When I read this in the e-mail and the text following it, my mind can't help but wander back to the first piece of text on the page that reads to me as "designers don't understand fun."

When I read your blog entry, I have this picture in my mind of having to adjust my game playing to change the difficulty to best match my idea of fun. I see the difficulty curve that ADD allows for in a game and think that by intentionally or subconsciously retarding how I play the game to make the game more fun for me, I'm intentionally making how I play the game more of an obstacle in order to make how the game plays less of an obstacle. And then theres no guarantee that the fun I can get out of the game by doing so is anywhere near what it could have been given the game engine and game design unconstrained by the ADD. Skill levels on the other hand allow me to adjust the difficulty to suit my idea of fun without necessarily having to retard how I play the game. Which isn't to say I wouldn't have to retard how I play the game, but that I guess I would have to retard it less and might gain an order of magnitude more fun out of the game because of it.

Like most other things, it probably comes back to how well the thing was done, rather than just the approach taken. Perhaps ADD can be done well. I could see it becoming am lazy and easy way out of properly play balancing as well.

What really ruins the immersion and immediately sucks the fun out of a game is the point where it becomes obvious that the difficulty is a pointless obstacle that serves only to slow down my progress in the game. Suddenly a game I was really enjoying feels like a shallow game, like dungeon siege or a bad space invaders clone, endless waves of targets I am forced to pointlessly and tediously kill. The beautiful environment that is the game becomes tainted by the bitter memory of how much fun it used to be before the illusion was destroyed. With skill levels I can choose to make this less likely to happen. Can ADD recognise this? I would be surprised if it could. Although perhaps its more often a case of bad design rather than unsuitable difficulty that causes this problem.

I haven't played Max Payne 1 or 2 and cannot say how well ADD worked for me in those games.

[Scott Miller]

Roger, ADD doesn't promise to cure cancer. And you're right that it comes down to implementation, and even if every game designer began to use ADD, it would take a few years before it would be done well on a regular basis. ADD presents similar problems that we find in creating good AI, and how many games have good AI-driven characters? Not many.

Still, with a little effort, ADD can be pulled off reasonably well in today's games, as was demonstrated in Max Payne, even with its imperfections.

-- "ADD introduces an element of variability at the rules that the player can easily identify as cheating."

Cebrian, there are numerous variable that can be changed that are less obvious to players. Also, as we did with Max, all variables had a min and max level, to ensure that they stay reasonable and less noticeable, such as the damage taken by enemies.

However, it'd be easy to avoid recognizable variability with a little extra work on the designer's part. For example, if the player is proving to be very skilled, then a harder class of enemy is used. This way it doesn't look like enemies that took three shots to kill a few levels ago now take five shots -- the game simply replaces the three-shot bad guy with the five-shot baddie.

Another tactic is to make changes slowly, nor jarringly. And boosting AI intelligence makes enemies harder in a hard-to-recognize way, such as making them better at diving for cover or better coordinated, as Gestalt suggested.

Another thing I'm all for is having a cheat available that overrides ADD, allowing hardcore players to set their own skill level if they prefer.

[Blake Grant]

I agree that ADD would work well in some games, but I still believe that there should be some level of difficulty that is adjustable by the player. I personally don't have as much time to play games as I would like, and as a result, prefer to play them on an easier difficulty so I can get through more of them. As you said, it should be about making the game fun for the player, and not everybody's idea of fun is the same. To one guy its being as challenging as possible without being impossible, to another its being essentially impossible, but pushing on anyways, and to another, its just going through and seeing the story, not wanting to be getting your ass kicked left and right.

I've played both Max Paynes (didn't finish the first one because I reinstalled Windows and didn't realize the savegames were in the My Documents folder!?). Loved #2. My favorite game of last year. In that case, I think ADD was probably working well. I didn't find it overly difficult. Its MUCH easier than the first one, and I blew through the game in about 6 hours. For me, the perfect experience. For many others however, they are annoyed the game is so short. As i said, everyone has a different idea of fun. Letting them decide for themselves how they want to play it is ideal.

One other note. This is alot like the old "should I let them save anywhere, or have checkpoints" issue. Games that only have checkpoints drive me crazy (I'm looking at you, XIII). The developer argues that people quicksaving and quickloading are ruining the experience by making it easier for themselves. So what? Let the player play it how he/she wants to. They put their money down, they want to have fun, not be frustrated. I see the same issue by removing selectable difficulty levels.

Just my 2 cents.

[Greg Findlay]

I think one thing everyone seems to be forgetting is that as players we expect the next level we play to be harder then the last one. So if the ADD system makes it more difficult to kill a guy on the next level, we would probably rack it up to the levels getting harder. This has been done in the past, and although I don't think it's the best solution, it works (using bars and not number to represent an enemies health helps this dillusion).

btw, Diablo and Diablo 2 both have rudementary ADD systems, it just assumes that if you're a higher level, your a better player and adjusts the monster difficulty level. Diablo 2 also adjusts to the number of players in the game. If you played either and didn't notice, then I guess ADD systems can work then eh? ;)

[JP]

In Diablo 2, monster levels for a given area are fixed, but the monsters you see in that area are randomly chosen from a short list. The only thing that varies depending on your level is how much EXP you get for killing those monsters.

Bumping up the monster levels in a game with >1 players has nothing to do with dynamic difficulty in a single player game... it's a simple, linear multiplayer game balancing equation.

Still wondering what it means for something to be "auto-dynamic"!

[Scott Miller]

JP, checking the dictionary, "dynamic" means changing (or able to change), and "auto" modifies this such that it can change by its own means. That said, I am not married to this name, so if you have a better one let's hear it. I often call this feature "self-adjusting difficulty," too. Perhaps I should have gone with SAD. ;-)

[JP]

The industry standard term for it is "Dynamic Difficulty Adjustment", or DDA. I've heard that term used by developers for at least ten years now.

[Tom]

I'm surprised that noone has mentioned Halo yet, or "The Illusion of Intelligence" presentation from the Bungie designers.
http://halo.bungie.org/misc/gdc.2002.haloai/talk.html

Halo is IMHO a very fine example of how to implement difficulty levels in a game: Easy allows the casual audience to complete the game, and Normal already provides a good experience with a few challenging parts. Heroic is pretty tough even for the hardcore FPS player, and then there's Legendary for the extra fun. Halo also proves that "Teaching by death" can work if used wisely, and thanks to the checkpoint based save system, the penalty isn't critical either. Players just get more psyched to clean out those enemies and will try different tactics to succeed, as intended by the designers.

The presentation also has a lot of nice thoughts on what players mainly associate with difficult enemies (mostly hit points), intelligent enemies, and how they tuned the game to have the fun (30 second scope). Halo is generaly agreed to be the best FPS with double emphasis on Shooter: combat is just pure fun and a lot of people I know played through the game several times just because of it.

The concepts outlined in the presentation seem to work, also supported by the ~3 million Xbox copies sold and as far as I know the PC version is a hit as well, even 2 years after the release of the original game.

[Sully]

My vote is for SARS.
Self-adjusting Response System.

[Brad Renfro]

Tweaking enemy health and attack damage fundamentally changes the game. If these variable changes are drastic enough, it warrants different playstyles and strategies, especially in the face of fixed enemy counts/placement and fixed ammoclip counts. It would be unfortunate if Max Payne's ADD caused players to play the game as a timid and careful hard-boiled cop :)

There could be other things you can tweak that will impact gameplay-style even less but still achieve results. Placement of medical kits may be the simplest. Players may be less prone to feel cheated with changing medkits. While a weapon's attack damage is something that is expected to be constant, changing placement of medkits isn't as predictable.

All of this reminds me of a virtual dungeonmaster, working in the background to give the player the best experience as possible. I think eventually, it could expand to cover more concepts than difficulty.

[JP]

The original Metroid's implementation of adaptive health parcelling (way back in 1986!) and Super Metroid's refinement thereof was excellent... any time you kill an enemy, the game checks how low your energy and missile levels are, and if they're below a certain threshold, a pickup will appear in place of the enemy. This logic was tuned nicely to provide the feeling that you always had to stay on your toes, but you could fight your way back from a deficit with additional effort. Increasing the damage enemies do to you is a less directly comprehensible and certainly less player-friendly way of accomplishing this and has the added disadvantage of being opaque to the player. I think part of the feeling of trivialized challenge people get from Max Payne's DDA is that they're never quite sure how much the game is helping them - casual players wouldn't necessarily care about that, but it might be a real negative point for dedicated gamers who want a challenge. Consider also that Metroid loses *nothing* by making it obvious that it's helping you.

[JP]

Err, my point being that the Metroid solution is more elegant, and happens per instance rather than at level load - thus more immediately adaptible. The player is ultimately better served if you can keep the behind-the-scenes meddling to a minimum.

[Gestalt]

Greg - "Diablo and Diablo 2 both have rudementary ADD systems, it just assumes that if you're a higher level, your a better player and adjusts the monster difficulty level"

I'm not sure that really counts - encounter tables in PnP RPGs have been adjusting the level and/or type of monster in an encounter according to the level and number of players in the group for decades. This is nothing to do with how good the players are, just how experienced their characters are and how big the party is.

[Scott Miller]

-- "The industry standard term for it is "Dynamic Difficulty Adjustment", or DDA."

Yeah, I'm aware of this term. I think it makes more sense as Dynamic Difficulty Adaptation. If the word "adjustment" is used, then the question remains, "Who is making the adjustment? The game or the player?"

The idea of giving or withholding health items is another way of implementing ADD without the player being aware. We could have fairly easily done this in Max Payne by giving more or fewer bottles of pain killer, depending on the player's situation when the come across a pain killer spawning point. Also, some thugs in Max drop pain killers randomly, and this could have easily been tied into the ADD system.

Again, there are likely dozens of good solutions, useful alone or in combination, to make ADD work like a charm.

Looking back, a mistake we made with Max is announcing ADD as a feature, because if players know it's there, they [1] blame it when the blame may not fit, and/or [2] try to manipulate it. Therefore, I think ADD will be more successful if unannounced as a feature. I'm sure that 98% of the game's players would never have known Max had ADD had it not been a bullet-point in ads and on the retail box.

[Jeff Mackintosh]

I'm sure that 98% of the game's players would never have known Max had ADD had it not been a bullet-point in ads and on the retail box.
-----
I think that's an important point that should be remembered. Many people seem to object to ADD because the player will notice it and feel cheated. I think the number of players who are sufficiently skilled and capable as to notice such manipulations of the game are enormously small compared to the overall purchasing base - I would guess less than 1% of an average game's purchasers would notice subtle manipulations of the mechanics. I feel, if you can make a game a better experience for 99% of the purchasing base while possibly annoying (since there's no guarantee that a well-implemented ADD will annoy the astute few who notice it...) the remaining 1%, you do it.

One thing that I often encounter in table-top gaming is game designers making games for themselves (this was much more common about five years ago than it is now, but it still occurs). I suspect this problem is common in video games as well. We, as designers of games, do not represent the average consumer, even remotely, and thus we should not be used as the yard stick...

[Walter]

Agree that it's best to not announce ADD. It's a lot like my disdain for highly publicizing the use of computer-generated FX(sorry JP! :D), which only makes audiences more attuned to what is and is not CG in movies, spoiling the experience somewhat.

Also, I happen to like "Auto-Dynamic Difficulty", which really seems to get at the heart of the idea, even though the context in which anybody would use "Dynamic Difficult Adjustment" makes it unlikely that anyone would be confused about who is doing the adjusting.

[Greg Findlay]

The health and damage that enemies do in Diablo 2 change based on the level of the character in the game, not just the number. The "boss modifiers" also change based on character levels. The sets of monsters that spawn in also changes based on level. D2 does more then that too but you get the idea :). It's not that sophisticated but I'd still say that it's ADD (or DDA if you prefer), because playing the same area will be more or less difficult based on your level. The only time you'll really notice it though is if you have a very high level character in a game with a bunch of really low level characters, where the high level character isn't helping the low levels.

[Joe McGinn]

"Re: Diablo, true it didn't have ADD"

The brilliance of the Diablo design is that it does have DD - Dynamic Difficulty. But it's not "auto", it's adjustable by the player in their choice of enemies.

If an area is too hard, you can go back to an easier level to earn more experience points and abilities for your character. This seems like an almost perfect solution. Everyone finds an appropriate challenge level ... the game doesn't have to make assumptions about what level of challenge is the most fun.

Having said that I'm a big fan of ADD in general. I think there is nothing stupider than a computer program that lets a player get stuck, unable to continue. Even a brute force approach is preferable to that, such as we used in The Simpsons Hit and Run ... fail a mission 5 times, and you get the option to skip it.

[Jamie Fristrom]

The points (1) and (2) you make are important. My question: how? I was playing Typing Of The Dead yesterday and discovered that it, too, does DDA. If I let myself die twice at the beginning of the level, it made the rest of the level much easier. So there was the exploit thing you mentioned, but also something more insidious: I did not feel like I was getting any better! The DDA robbed me of the feeling that I was learning! I was playing the same level over and over, dozens of times, and I never got good enough to defeat the final boss. I finally realized that as I was getting better, it was getting harder.
I prefer the Noah Falstein tactic - "parallel challenges with mutual assistance" - to DDA. This is something the Zeldas and Marios and Diablos--hell, even crossword puzzles--do that does not rob me of my sense of accomplishment. In fact, as I upgrade my character or fill in the puzzle, it's almost as rewarding as learning a new skill.

[Mark Ventura]

A good example of how NOT to do it: BloodRayne.

In BloodRayne, if it takes you more than a certain number of tries to get from one checkpoint to the next, it just increases your health. It's obvious. It happened to me once, and it made me feel robbed and a bit insulted.

[Nathan McKenzie]

I think another way that you could implement DDA and still retain feelings of achievement is to actually take things in the complete opposite direction - make it completely, totally opaque to the player. Even give them an actual score of how well they're doing. Then, casual players could still play through the game and enjoy themselves with the game tuning itself as they go, but hardcore players would have a new goal to set for themselves. It would actually be pretty similar to the way that a lot of recent Capcom games give players letter grades for subsections of games (I think lots of recent Japanese forced-progression 2D shooters, like Ikaruga, do this as well).

So, the good player starts doing well, the game starts becoming more challenging, trying to match the player's skill and keep them on the cusp of their ability... BUT the game also acknowledges to the player, "Hey! You kick ass! And there are even higher ranks to achieve if you can overcome this new level of challenge!"

I haven't actually gotten to try this out, but in my head it seems appealing. I doubt it would be ideal for all games, of course - but I do think it might be a really viable way to go for some sorts of games.

[Scott Macmillan]

Jamie, can you explain exactly what the parallel challenges thing is?

[Nathan McKenzie]

Er, I perhaps meant completely, totally transparent, rather than opaque, in my previous post. Maybe. Or let's go with "completely, totally obvious". That will do.

[JP]

I agree with the basic principle behind what Nathan (long time no see sir!) is saying: if there is an Invisible Hand try making it a visible gameplay mechanic. If the casual player is indeed just playing to get through the story (an assumption that may be incorrect; more a product of the content-driven paradigm than the nature of casual gaming, but that's another discussion) he won't care if the game is giving him a "C Ranking" - or you could even phrase it in less negatively-reinforcing terms (you are AWESOME, but there are five full ranks of AWESOMENESS above you!) - whatever, so long as he gets to "win" the game in the end. Then the more dedicated gamers who care about skillfull play still have something objective to strive for. Of course if your gameplay is robust and interesting anyway then dedicated players will even make up their own challenges - speed running, making it through the game without getting hit / on one credit, etc.

By providing a range of objectively-measured skill tiers, which the game visibly shifts between based on player performance, you get the best of both worlds - it needs to be established in gameplay (and in the world fiction, if the game has a story) though, otherwise it will seem like ancillary complexity.

The ranking doesn't have to be an incremental thing either, it can just be an approximation of a floating point variable (which might be a bit more algorithm-friendly for subtle degrees of adjustment).

[Scott Miller]

JP, if you refer back to my original email to Remedy (at the very end of it), you'll see that I already considered the idea that the game track the player's ability, since the ADD system could easily keep measurements of it throughout the game, and then produce an interesting graph of the player's skill. A player would typically start off weak or average, and then as they got better the game would compensate, and thus on a graph it would show that the game ramped up its difficulty over time.

Such a graph would also reveal sections of the game that are particularly hard, such as the building-on-fire level in the original Max, where most players experienced repeated deaths. Likewise, easy sections would show up on the graph.

A nice graph of the players progress could be examined at any point during the game via a cheat code or special menu option.

[Jamie Fristrom]

Sure. The "parallel challenges with mutual assistance" was coined by Noah Falstein in an issue of Game Developer - it's just saying, give the player multiple challenges they can choose from, and completing one challenge will help them complete others. So almost every game with RPG elements does this by letting you take on side quests that give you power-ups. If you have trouble on one quest, you back up and try another. Crossword puzzles do it at a more micro level - filling in one clue sheds light on the others. The RPG model still isn't perfect - some people don't want to backtrack - I never beat Chrono Trigger because I didn't have the patience to build my character up enough to beat the final boss - and it's also a little backwards: the kind of players who like doing side quests are often also the kind of players who are good enough to get through the game without the extra upgrades. And, like DDA, character upgrades are another illusion - replacing actual progress (you really are getting better at the game) with fake progress. Still, it's more to my taste than having the game adjust under the hood.

[Joe McGinn]

"Er, I perhaps meant completely, totally transparent, rather than opaque, in my previous post. Maybe. Or let's go with "completely, totally obvious". That will do."

See today's Far Cry single-player demo ... along with Easy/Medium/Hard, you can choose whether the AI auto-adjusts. Great AI in this game BTW!

[Brad Renfro]

"Then the more dedicated gamers who care about skillfull play still have something objective to strive for."

In the realm of FPS (especially among the hardcore), the public perception seems to point to singleplayer mainly for narrative content, and reserve multiplayer gaming for any true tests of skill. In single player, a player's deficiency of skill often results in anger towards the designer (calling the game unfair and unbalanced) and sometimes a halt in seeing more of the game.

"I think lots of recent Japanese forced-progression 2D shooters, like Ikaruga, do this as well"

Many Japanese shootemups also encourage difficult playstyles through optional gameplay mechanics to appeal to the hardcore. Like Ikaruga's chaining mechanic encourages lots of onscreen movement and risky bulletdodging, but is not required to complete the game. Unfortunately, I think Japanese gaming culture is more likely to embrace such concepts.

[JP]

"In the realm of FPS (especially among the hardcore), the public perception seems to point to singleplayer mainly for narrative content, and reserve multiplayer gaming for any true tests of skill. In single player, a player's deficiency of skill often results in anger towards the designer (calling the game unfair and unbalanced) and sometimes a halt in seeing more of the game."

I don't quite see what you're driving at... how does this relate to the DDA scheme I mention?

[Brad Renfro]

"I don't quite see what you're driving at... how does this relate to the DDA scheme I mention?"

That the scheme wouldn't be a much used feature in narrative-heavy games such as most modern FPSs, and may even serve to break immersion in games such as Half-Life or Halo. But now that I think about it, it's a relatively small simple system which would probably fit well in other current FPS games. Never mind :/

[Tim]

I few years ago I wrote a game called 'Hunt for the Red Baron', a WWI arcade aerial combat game. It had a simple difficulty adjustment system whereby it would count how many times you've unsuccessfully tried to complete a level in a row. It would slightly adjust your plane to be able to withstand a bit more damage and the enemies a little less every time. It would also make very slight adjutments to the game speed, slowing it down to make it easier to react every time. The effect was very slight, and not really noticeable. I think perhaps I should have made it ramp up a bit quicker as I still get mails from people stuck on level 12 & 15. Well, that or re-jig level 15, I suppose...

[JF]

Like most of you have pointed out, ADD does have it's flaws. It definetly doesn't make the designer's job easier. The designer will have to work hard on balancing ADD. However, by using add you eliminate categories. A player is not forced to judge weither he's fit for the normal mode or the easy mode.

It also allows for infinite levels of difficulty. We can compare it to shopping for shoes. What happens when you're stuck between two shoe sizes? You have to live with the bigger size hopping your foot will grow. With a well balanced ADD system players will always be chanllenged to progress and improve their skills.

A good example of a game that should use ADD is Tony Hawk Pro Skater. There is always room for improvement in THPS. Advanced players could easily go thru the game's hard mode without challenging their skills.

It's all about balance. And if done correctly, there's no doubt ADD is more efficient then fixed difficulty levels.

[Sean]

PLayed both games of Max. Excellent btw.

but in MP2 it was sometimes apparent when I did very well that thing got harder. (couple of time I would shoot guys point blank with shotgun only to have them stand back up... disconcerting when you have already counted them KIA)

But overall the adjustment process was well implemented.

It is a good process, and helps those of us who can't put 40hrs a week into games
/my 2 cents

[Gel214th]

Umm....if the problem is making the game possible for less skilled players to complete...why not just include cheat codes with the game that players who are having a hard time getting past a certain point can use?

Play balance the game of course, but cheat codes would allow a particularly poor player to still complete the game.

THe codes could also manipulate the game to make it more difficult for a truly 'hardcore' gamer who may think that the game was too easy.

Obviously a lot of people see the need to use Cheat codes to enhance their game experience, hence hte popularity of Trainers for the PC where codes are not included in the game, and software and hardware like the Action Replay for Consoles.

[Walter]

You got /.ed!

http://games.slashdot.org/games/04/01/23/0256230.shtml?tid=127&tid=186&tid=206