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Game design

Iterative 2-layer health bosses

written 2025-02-05

A common type of boss design in action games: it has an outer health bar and an inner health bar, you have to deplete the outer one to make the inner one vulnerable for a few seconds, and then the outer one refills.

This type of boss has some problems.

Firstly, if the player can have many different levels of damage upgrade or equipment when they face this boss, the effect of those differences is squared: if they get to the boss with a weapon that deals half as much damage as the designer expected, it'll take them *4* times as long to kill the boss, because it takes twice as long to empty the outer health bar and they have to do it twice as many times. This can lead to some players having a far more tedious experience with the boss than expected.

This also applies if someone has a character build or playstyle that just isn't good at dealing a lot of damage quickly, or in certain situations (for example, if the boss hovers in the air while vulnerable, players who've upgraded attacks that only work on the ground are screwed over).

Finally, if a vulnerability window can be skipped, such as if the boss floats around randomly and can go into a wall so the player can't reach it while it's vulnerable, that can be very frustrating to the player since they went through an entire iteration of the outer health bar for nothing.

However, all this doesn't mean that iterative 2-layer health bosses can never be good. I'd like to highlight Goumang in Nine Sols as a good example. She has 2 minions fight you on her behalf, and only comes out to revive them when one of them is down. It's early in the game, so it's unlikely the player's build or playstyle has diverged toward dealing a lot more or a lot less damage than expected. And the way it works creates a lot of room for interesting strategy and tactics:

• The 2 minions are very different, so it's interesting to decide which one you want to focus on. One moves faster and so is easier to attack (because he tends to end up in front while the minions are chasing you), the other has more upward attack potential making it more dangerous to have him right under Goumang while she's vulnerable.

• There's a delay before she comes out, so you can use that time to try to lure the remaining one away from where she'll appear so you can attack uninterrupted.

• She comes out when either minion is down but can revive both at once, so you're wasting damage if you down both minions at once, but on the other hand, doing that means you have no one attacking you while you attack Goumang, so it can be a good strategy.

• She stays out long enough for several combos, so even if you're getting hit and knocked around when she appears, you'll probably still have time to get at least some damage, so it's not as frustrating as it would be if you could completely waste a vulnerable phase.