Fractional Invincibility

In intense action games, from classic platformers to punishing modern RPGs like Dark Souls, surviving a massive enemy attack often relies on a deeply counterintuitive maneuver: rolling directly into the swinging sword. Visually, the blade passes right through the characters body, yet no damage is taken.
This is the magic of the "Invincibility Frame" (I-Frame). Developers realized early on that pixel-perfect evasion was impossible for human reflexes. To make combat challenging but fair, they hard-coded a mathematical grace period. During specific frames of a dodge animation—often lasting mere fractions of a second—the game engine temporarily turns off the players hitbox, making them completely immune to the physics of the virtual world.
This book breaks down the extreme mathematics of action combat design. You will explore how fighting games balance risk and reward down to a 1/60th of a second, why removing I-Frames turns a fun challenge into a frustrating chore, and how elite speedrunners exploit these mathematical gaps to literally walk through solid walls of fire.
Master the invisible math of your favorite games. By understanding the precise engineering of Invincibility Frames, you will see digital combat not as a test of reflexes, but as a high-speed rhythm puzzle.