How do you do hard mode difficulty setting?

Difficulty setting exist in effort to please everyone. Some may want to break through everything with easy mode because they don't bother with trying to explore the mechanic, and want a simple way. Some prefer a harder difficulty for many reasons.

That said, the normal difficulty is usually made for the intended experience.
Then, there're people who think "Can this be harder?". There comes "Hard mode".
The problem arises. The normal difficulty usually made as fair as possible. Beyond that players may experience unfairness. With that said, Hard mode often feel like it's hard for a sake of being hard. Or players need to play a specific niches.

How do you balance these difficulty settings?
Do you use normal mode as a standard balance? Then later try to bump it up for hard mode?
How do you ensure hard mode is still manageable without being frustrating?
What did you do to your hard mode difficulty setting in your game (if you have any)?
Did you boost enemy stats? Or did you put extra enemy pattern for harder mode? Or both? Or another method?
Or do you start with hard mode as standard balance, then tune it down for normal setting?

A bonus question:
What makes a hard difficulty good or bad?

Honestly I just plan everything for normal difficulty (like everyone). For easy mode (can be selected before creating a new game and can't be changed through the game), I simply nerf the enemies' stats (I'm testing with different coefficient. For now I think 0.75 is good).

There is no hard mode. The real "hard mode" comes after the game has been completed. The player will unlock many side quests that are much more difficult than the main story.

First, a quick disclaimer: because this could evolve into something more substantial (and trust me, I've had it happen) my guess is that you're better off discussing this in plugin requests for your targeted engine (VX, MV etc.)

With that said, and seeing as this would likely require plugins I recommend enemy levels from the Yanfly suite if you just need the balancing portion or you can use either its matching difficulty slide scale or this one from bluebooth if you need something extra. The rest is actually up to you - do as you think is tolerable. And implementing a hard mode option (or even a new game plus[1]) can add replay value by its own extension.

In my case (and this can be added onto anything else including what @MushroomCake28 suggests) I have a second quest mechanic that starts immediately following the main plot with a focus of defending your hard work the first round through (or you can simply crack the case of my ultimate secret based on its clue in the game's achievement journal[2]). And before I forget, please note that in either case you don't want too much in the proverbial oven, and that's primarily because you obviously don't want to **** off your customers by shipping a ridiculously unbalanced game.

1. You'll also need to extend your save menu for this concept to be of any real use.
2. This one's specific as it is historic, according to my in-joke. But if you really want to know...
   Spoiler

   UUDDLRLRBA

Base on my favorite game Valkyrie Profile (ﾉΦωΦ)ﾉ
I think Hard Mode = include some new Enemies & Stages & Equipments
Enemies get stronger >>> you need to grind level much harder in order to beat them
(About unfairness because of over power Enemies, there is one way to help that's include an Timing Defense system or something - which require Player's skill rather forcing him to grind)

@BreakerZero I'm not requesting anything, so this will never go into specific engine support. I just hope this discussion will be benefit for everyone who use different engines.

Your first paragraph is like saying "Well just use these plugins, and tweak it until you feels it's right". I hate to break it to you but it's not the answer I was expecting. Again because this isn't an implementation discussion. The more implementation solution put onto the table restrict you to imagine more because it will be driven into "This specific implementation / plugin is not capable of doing that". It's more into conceptual level on how to concepting a hard mode. Not about how to implement hard mode. And to be fair, your second paragraph did answer the question, so thank you for participating.

EDIT:
@Isabella Ava
More enemies for hard mode sounds interesting. It will create more work, but still interesting regardless.

What I often see in games for hard modes are usually enemies with buffed up stats (often HP, sometimes more and new skills or mechanics).
To compensate, those games also offer more reward for overcoming the hard mode challenges (exclusive equipments, special dungeons, ...)
So this seems to be the "popular" way of doing it.
As for what I think, it seems fair to somehow reward the players choosing to go for the hard mode. Aside from the challenge itself, they should feel it was worth it in some way. So some form of exclusive content tied to hard mode only should be there. That way you not only tempting the challenge addicted players but also the more "casual" who might be intrigued by what's in it for them.

I've never finished a game, but I'll try to answer with how I go around stuff.
Yes, normal mode is my standard balance. It makes the most sense as well, since it's a stupid idea to base a game on easy difficulty (hehehe) and basing it on hard would be even worse. You want to balance the game on normal difficulty and then make subsequent difficulties based on that, because normal people should eventually be able to beat your game (maybe not in their first playthrough, but it shouldn't take ludicrous amount of time and playthroughs). And therefore balancing the game from easy or from hard difficulty would have distorted your view. However, before I balance the difficulties, I want to first make a draft on how these difficulties will differ. In an RPG it'd be more intelligent AI and extra spells for example, in strategy games more intelligent AI and nerfs to the player (with the emphasis on AI though, more on that later).
That's a silly question I would say, no offence. It's hard mode, it should feel like hard mode. People can beat hard mode, because they know the game inside out and have spent numerous playthroughs on perfecting their in-game skill and searching for and exploiting weaknesses in the game mechanics. If you have people actually beat your game on proper hard difficulty, it's rewarding for both them - they defeated your game - and for you - you made a game engaging enough for people to really invest time in. Making a hard difficulty not frustrating will not feel as rewarding for beating it.
If the only difference between normal and hard difficulty is that you don't grind 20 minutes, but 2 hours, how can you call that difficulty?
Boosting enemy stats yes, but not excessively. More importance is put into enemy attack patterns and the AI's intelligence. I'm not even afraid of being really nasty and implement instances of human-ish intelligence as well, for example: Attack enemy healers first. Focus on weaknesses, it's useless to cast fireball against fire mages. Without mana they are screwed, take it away from them!
Normal difficulty might be more forgiving, but I make sure that hard "forgives no mistakes" (it's a bit of an exaggeration). I also try to make sure that apart from grinding yourself to getting OP there's no "one and true way" to defeat the game. For example I am not too fond of having a closed skillset (i.e. level 4 learn fireball, level 7 learn fire blast, which is an improved version of fireball, level 10 learn fire storm,...), because closed skillset will take away from the creativity you may have (since you have to allow the boss to be beaten). With dynamic skillset you can employ wide varieties of enemies, some of which may even require different skillsets (since I find the idea of having to respec 3 times a game to beat it ridiculous, I prefer making learning skills related to equips or items).

A good hard difficulty on my book is real difficulty. When you need to fight your way through. Spend time learning the ins and outs of the game. Think outside of the box. Although I hate it when there's only one way to defeat it, since it kills creativity.
And two biggest turn-offs for me are artificial difficulty (i.e. when the only difference is in boss having greater stats) and difficulty not worthy of its name. Unless it's a skill based game, I shouldn't be able to beat it on the first try on hard difficulty (and even if it's a skill based game, but due to skill occurences may happen).
Oh and I also hate it when the game can be exploited using common exploit mechanisms (for example rushing speed in ATB to have more attacks or item spam)

I haven't put much thought into doing a "proper" hard mode. What I'm considering doing instead is making my game beatable at level 1 by giving players a way to avoid gaining EXP (such as through an accessory). In theory, it'd accomplish the same thing as a "proper" hard mode: providing an extra challenge to those who would desire it, while also saving the developer the effort of having to create multiple versions of each enemy. Granted, this would also mean you'd have to put more effort into balancing the player's stats and equipment.

If I were to do a proper hard mode, I'd probably mix things up a lot more than just altering the enemy's stats (or the player's stats, for that matter). Heck, I might not even mess with the enemy's stats at all. What I'd likely do instead is make the enemies a bit more intelligent in using their tools, or give them some new skills to play around with that they wouldn't have on normal mode. Perhaps some enemies have a completely different behavior on hard mode than they would on easier difficulties (although by that point maybe I'd be better off creating a new enemy entirely for hard mode).

But why stop at the enemies? Why not mix up the dungeons and general world layout, too? Perhaps there's an in-universe reason for a service available on an easier difficulty to not be present on hard mode. Or perhaps the circumstances in-universe actually have a greater impact on the gameplay in hard mode. Perhaps the looming, world-ending crisis can actually cause a Game Over in hard mode if the player wastes too much time on sidequests?

Basically, I'd want a proper hard mode to actually be just as fulfilling an experience as an easier mode would be and actually offer players something that makes it worth it over an easier difficulty. "Hard modes" that simply make enemies hit harder/make the player do less damage aren't really fulfilling, in my eyes.

@BreakerZero Please remember that Game Mechanics Design is for looking at aspects of game play at a more conceptual level. It most specifically is not about implementation which always belongs in the appropriate Support forum. Please therefore do not post implementation answers in this section.

I currently only have one difficulty, but ideas I've considered are the following:

1: Give the player an option to set both stats and progression difficulty. My first versions of my demo had an option to pick 5 difficulty levels for the monsters where monster stats were -50%/-25%/0%/+25%/+50% all stats *but* HP. I personally don't like higher difficulty = everything is an HP sponge now, so I only upped the other stats. Then they also could pick from 5 progression difficulties which affected how much EXP and G they earned in battles (lowest they got 2x as much from all fights, hardest it was 50% as much).

Sure, if someone felt like it they could pick the hardest for both. But I did remove it at some point as I wanted to focus on balancing the default game first. Maybe I'll readd it, not sure yet.

2: One thought I've had is to maybe do the following instead though for difficulty:

Easy: Give the player some auto-revive items at the start of the game. If you ever played Persona3, that is what they did, you got 10 Plume of Dusks which would revive the party with full HP and MP if you were defeated. But you only had 10, and as far as I could tell you can only earn 1 more in the entire game, so use sparingly. Now, you could do something similar, where on Easy maybe the player gets better equipment, or more aids or something. Or maybe more little things like "Here, take this nice Enchanted Sword I have laying around. I don't need it anymore." That would be one way to make it easier without making monsters total jokes to defeat.

Normal: Default game.

Hard: All helps are gone or heavily reduced. Maybe this could be you have less loot in the dungeons now. Or less merchants willing to help out in strange places (who sells in the middle of a monster infested swamp anyways?). Or maybe bosses have 1 more helper which really changes what you have to do to win the battle (incidentally, in my game, most bosses are either 1 boss vs 4 players or 4 enemies similar in strength to the party vs 4 players, so suddenly going to 5 vs 4 could really change things up).

I don't have a hard mode. I have game and story mode. The only difference between the two is that game mode has perma-death while in story mode fallen units (unique ones anyway) recover in-between battles. Story mode completely breaks the game in my opinion because the game is balanced as a sort of hybrid between civilization and final fantasy tactics but I've been on enough discussions in the past to realize that 9/10 players won't abide by perma-death of story characters.

I got 5 modes. Player chooses what they want at the start. Can't be changed after selection.

When it comes to difficulty in my game-in-progress, I'm more inclined to just give the player a "Normal" mode and a "Hard" mode. No easy mode. Normal is, of course, the intended difficulty that's mostly fair. There's bound to be a large handful of challenges to overcome before you can reach the end. A lot of developers tend to get Hard mode wrong, though. Very, very wrong.

Difficulty =/= Higher Stats. It's much, MUCH more than that. A Hard mode that just makes enemies deal more damage and take less damage is a failure of a difficulty selection. True difficulty comes with making enemies smarter (making them target healers more often, finish off low-HP allies, use their strongest attacks more often, etc), increasing the amount of enemies you fight / switching up troops so that the player has to deal with brand new formations and plan accordingly, and giving enemies new skills and mechanics. Wanna give your Hard mode some flair? Make that goblin RESISTANT to Fire instead of weak to it. Give that low-level slime a new Crowd Control spell. Make the player fight 4 orcs instead of 2 when they ambush them on the bridge leading to the boss room. Give that Boss battle a phase 2 unique to this difficulty setting.

Yeah, it takes effort, but it'll make your game so much better in the end instead of taking the easy way out and saying "Bad guys now have more HP and ATK. Good luck!" That's just lazy design.

In my game, I have "Tempered" enemies in the normal game.
They're simple: more stats
The main draw of it is that aside from higher stats, they get new skills and mechanics as well as a better AI
Now they will do everything they can and use optimal strategies.
Since this is present on normal as a challenge, the hard mode would simply make them spawn 100% instead of something like 15%
Now suddenly, every fights are a challenge and gives me the opportunity to develop more interesting take on the same playstyles from each enemies

I'm trying to take the Mario approach, which means you can complete the game without too much trouble, but there's always going to be tricky jumps with special coins just out of reach to someone who just wants to stroll through. In other words, I'm not using a difficulty setting because I don't want players to feel obligated to choose easy if they just want to enjoy the story, or hard if they want to get the most from every fight, potential hard-only boss achievements, or whatever. Instead, the difficulties will be implemented something like this:

Easy: The game starts out this way, giving players a chance to get a feel for the gameplay, before progressing to Normal.

Normal: Enough tactics are required to keep the player engaged, but everyone should be able to experience the story from start to finish.

Hard: Bonus super-bosses, secret areas with extra-challenging foes, etc. Of course, care will need to be taken to avoid the inverse difficulty curve created by taking overpowered bonus area loot into the standard chapter progression.

In my experience I've always balanced for my hardest difficulty primarily; what is the most difficult I can achieve as a developer that also doesn't make me angry when I play? If I struggle with it, I generally don't expect my players to endure it either.

When it comes to Normal I basically ask myself the same question - but instead of what will make ME less angry, I try to put msyelf in the shoes of a first time RPG player - what will they experience? Of course when looking at normal you are also looking at the perfect balance, trying not to be too easy just as much as you don't want to be too difficult. So you need to think of how to not bore your player while at the same time not groundpounding them with difficulty.

In the 3 games I've worked on personally I discarded Easy mode for Narrative mode. I find there's no point making a game super easy for no reason - generally if somebody wants to play on Easy they just want the story, so Narrative mode is generally much better suited to this type of player. To me this means stripping combat mechanics and stat/equipment mechanics almost in their entirety.

To me the difference between my Normal and Hard often comes down to use of buffs/debuffs and special synergies between these mechanics. Normal will place much less emphasis on needing to buff/debuff, whereas on Hard it would be mandatory. I try to avoid spongy enemies the best I can, but at the end of the day it's almost unavoidable. So instead of making simple damage sponges, I try to make them more... tactical sponges? I want the player to think about their moves several turns ahead in Hard mode, where to me Normal should be the carefree experience.

All of this is why I balance for Hard mode first. To me Hard Mode means the most in-depth development of combat and abilities and making sure it all works at its "highest" level of function. It's much easier to compact stats and mechanics downwards, in my opinion.

Bumping this topic because I find this is interesting.

In my project at the moment (this is open to change as I progress), setting the difficulty simply changes how much regeneration you get after each battle. Easy gives you full HP and MP regeneration; Normal gives 1/4 of max HP and 1/8 of max MP; Hard gives none. (States don't come into it as I have no states that persist after battle in any case.)

Like Revival, I play on Hard first to make sure it's balanced, in terms of it being possible to maintain a good enough stock of healing resources to keep going if the player makes sensible choices -- I have an advantage here in having designed the game, but the point is that it's possible to learn what are sensible choices through play, and I feel there are two types of player who would choose Hard: either they already know the game through having played Normal first, or they want to learn as they go and don't mind having to do a bit of learning through mistakes. So I feel that if I can complete Hard without it being too frustrating, it should be about right, and Normal is likely to be about right for new players -- but of course I take feedback from others into account as well, especially for Normal.

@Aoi Ninami : That reminds me of how Xmorph did difficulty. Easy your base (called the core in that game) had the HP fully restored between waves, and each level after that it was 25% less HP restored, which meant the hardest you got none at all.

How i implemented hard mode:
Nerf certian skills. Limit number of healing items. Give enemies new attack patterns and slightly higher health. Make items 15% more costly. Take out ultimate items.
Take away revive items.
Yeah it's difficult but doable ;)