Phase isolation is bad design

written 2026-05-17

I'm going to complain about a practice in boss design that I'm calling phase isolation: where events that happen in one phase are not allowed to affect the next phase.

For example, in CrossCode, bosses are invulnerable until you do something to make them vulnerable for a few seconds. These "vulnerable windows" take much effort to create, so they're balanced so that you can usually do a lot of damage during them, sometimes an entire phase. But what if you do *almost* that much? if you leave the boss just a few hp above a phase boundary? Then you have to wait for the next vulnerable window, and when it happens you finish with the phase with your first hit... and then the vulnerable window instantly ends. Vulnerable windows are not allowed to span phases. This is phase isolation.

It's very frustrating when it makes you waste most of a vulnerable window, but it's also bad because it reduces the range of meaningfully different outcomes that can happen. It makes it so dealing 99% of a phase's hp in one vulnerable window is no better than 50%. It makes it not matter whether you attack efficiently or not, as long you're within that big range.

It's also a balance nightmare because it makes upgrading your damage not matter at all until suddenly you go from 99% to 100% and it *doubles* your effective damage.

Phase isolation is bad design, and it's artificial (you have to go out of your way to do it). Just don't do it.