When to shoot twice: XCOM's Rapid Fire probabilities broken down

You're near the end of an especially hairy XCOM: Enemy Unknown scenario. An alien has one health, and you have an Assault specialist in firing range. Should you use the Rapid Fire ability for two shots at a 15% reduced hit chance, or take one shot? You could make the decision with your gut, or you could do the math, as University of Kent Research Associate Neil Brown has done. In a blog post today, Brown answers that question and others with numbers and glowing probability graphs.

I won't embarrass myself by attempting to explain Brown's math, but you can see the equations on his website . He also (almost definitely correctly) points out that Firaxis must have done the same math when arriving at the 15% Rapid Fire accuracy penalty. That's no surprise, of course, but a reminder that nothing in games is arbitrary. Though I tend to get lost in the surface-level war metaphor and make gut decisions, the best possible decision in any game comes down to the numbers at play—XCOM just puts them on the surface for us to poke at. And by "us," I mean people like Neil Brown, whose mathifying I can enjoy.

Tyler grew up in Silicon Valley during the '80s and '90s, playing games like Zork and Arkanoid on early PCs. He was later captivated by Myst, SimCity, Civilization, Command & Conquer, all the shooters they call "boomer shooters" now, and PS1 classic Bushido Blade (that's right: he had Bleem!). Tyler joined PC Gamer in 2011, and today he's focused on the site's news coverage. His hobbies include amateur boxing and adding to his 1,200-plus hours in Rocket League.