Invincibility Frames (I-Frames)

Brief moments during specific animations, typically a dodge or roll, where a character's hurtbox is disabled, making them immune to all damage.

In games, this means

Dark Souls' roll is balanced almost entirely around i-frames: players learn to time rolls to the exact moment of an attack. The mechanic is invisible but fundamental, without i-frames, the roll would be a positioning tool only. Communicating i-frame timing poorly makes the mechanic feel like a glitch; teaching it well makes it feel like mastery.