The only instance where I used Additional Turns was on my Slayer Character. He gets a special ability which makes him Invulnerable to damage and goes on a Rampage spamming all of his skills for 3 Turns. This was supposed to be his Ultimate Ability and it would be on Auto Battle Mode so you can't control him. Other than this, I don't like additional turns in a Game, Its game breaking.
Of course, There is Additional Attacks in a single turn, which is quite different. I make use of it on my other Classes like Gunner who gets to do the default attack 2 times in a row.
I use them for my bosses because if it's like 3 against 1, I want to make sure my boss has the ability to at least act twice. Levels the playing field a bit.
What I like about additional turns for an actor is that you might be able to instill combos in your game for higher damage. And if you design the game so that inflicting damage is satisfy (like in a combo), then it could be a lot of fun. Octopath Traveller did this with its boost mechanic. Xenogears also did this with AP to deliver death blow after death blow. But what it means is that bosses (and maybe enemies) have huge amounts of HP.
Sure you can make any mechanic to "break the game" but if designed well, it could be a fun mechanic to add to the game.
it's a good balancing tools, but in equal PvP format, it's rather annoying than fun.
focusing on single-player games, I think it could work, like single boss that fight your 3-4 party members, like giving them "1.5 action". extra turn doesn't always mean double attack. you could make attack and debuff action, so the boss still got the edge.
another form of extra turn could be something like bravely default/octopath or saving action point for future turns kind of mechanic.
I only really do additional turns for bosses, because giving them 1 action a turn against a player party just isn't going to cut it without cramming in a bunch of effects into a single move. If I give an additional turn to a regular enemy, it's more as a passive ability, like a vampire enemy who summons a bat minion each turn.
For the player, I don't do additional turns, just because the player already has a party of multiple characters. But I could see it useful in games that feature 1-man parties.
First of all, it's worth considering that many of the greatest games ever made operate on the one turn, one action principle - Chess, most versions of Pokemon, (Limit) Poker, Spectromancer, and so on. Holding that rule sacrosanct (or making rare, temporary exceptions to it - e.g. castling in Chess, or playing Timeweaver in Spectromancer which allows a spell to be cast as well on that turn) is what allows the concept of game pace to become an important dynamic, and ensures that each side will always have the opportunity to respond to the other side's actions. It also forces synergies between actions to require a setup (and in the case of a competitive game, a "forecast" of the player's possible intent), rewarding the player for thinking a few turns in advance instead of having things fall into their lap.
Moving too far from that dynamic can be disastrous, as proven by the abundance of OTKO (One Turn KO) decks in CCGs like Magic: the Gathering and Yu-Gi-Oh!. These became so bad for play that Restricted rules had to be added for tournaments to limit/remove the cards that are most likely to enable OTKOs.
So with that said, I am generally against giving additional turns/actions to battlers in RPGs, except occasionally giving bosses two consecutive actions if it's a single boss enemy against a 3+ member party. Exceptions to the rule can be fine as long as they are challenging to trigger - a couple good examples that were brought up in this topic are 1-More's in recent Persona games (for landing a Crit or hitting an enemy Weakness), and Limit Breaks (Trails in the Sky is notable and kind of cool in that it allows you to interrupt the flow of battle to use your Limit Break whenever you want). Exceptions can also be made if there's a heavy malus effect for taking extra turns, such as Overclocking in Bravely Default.
I would never make, for example, an equip that allows you to unconditionally act multiple times in a turn, because it would be entirely gamebreaking. If I did feel compelled to add something like that, the only place it could work is sometime after the final boss is defeated, because after that point it's okay to throw game balance out the window and let the player go wild.
"CTB" style battle systems (which are essentially streamlined ATBs that pause and let you breathe when it's time to select an action) are completely exogenous to this concept because there is no concept of a turn outside of the action that the battler takes. I think it's fine for a speedy battler to be able to "lap" their opponents in such a system, thus taking two or more turns before the opposition can respond.
@Wavelength Wow, thanks for all the examples! I haven't played all those games you mentioned, but I'll give them a look. I appreciate what you said about synergy, and about forecasting intent. I'm beginning to believe (certain) bosses with extra turns could have a similar forecast system, to give players a chance to prepare for what could otherwise be a OHKO.
In general, what is the opinion on a piece of equipment that grants an additional turn if the player receives a certain negative state, or if the hp falls to a critical state in one hit? Any immediate and obvious exploits with that?
I actually have a piece of equipment that does that. It strikes twice, with the drawback being that it nerfs your maximum HP.
However, the way I've tended to design stuff... it's "overpowered" and meant to be. To an extent. After all, HP doesn't matter if you kill your enemies with the first actions. It also doesn't matter if you have a lot of Defense. So, the item itself has very little drawback from that standpoint.
Now, it isn't really an "extra turn", but the effect is similar, since it hits twice.
But, it's only obvious "weakness" is attacks that do a significant amount of damage, states that immobilize that player or hinder their damage output, or an encounter with a lot of enemies that have a chance to exploit the low amount of HP the character has.
I think you'd have to be quite careful with how you try to "balance" extra actions as they can result in a serious amount of easy battles. You often need to balance HP/Defense values to account for these extra turns, even on regular enemies, or have to sort of normalize the gameplay loop of, "I go extra times and easily win the fight". Or, you could work around it through gimmicks and other forms of gameplay. But, you have to be careful as extra turns drastically changes the dynamic of "difficulty" in a game. Usually exponentially. Every active stat point is essentially doubled when you get an extra action. Instead of healing 100, you can heal 200. Instead of doing 100 damage, you can do 200. You'll need to carefully regulate the stats upon level up or on your attacking equipment just to prevent the exponential increase of damage from extra turns.
Hi @Tai_MT thanks for your insight!
I'm all for powerful stuff; I love difficult games and designed a difficult game. You better have a good strategy if you want to survive kinda deal. I appreciate you pointing out the potential weaknesses of a low health conditional extra turn, and believe it can be balanced into my game. It's intended to be a rare equipment effect, and only in late-game. Early to mid-game, the enemies require a set-up before dealing that much damage, and at that point, if you aren't prepared/paying attention, they tend to kill the party with their set-up anyway.
I'm more thinking of this effect as available only prior to the final boss, who can and will chew through over half your health. The effect is intended as a way to offset/counter some of the final boss's more potent attacks.