to web browsers, making it totally free!
But perhaps you're not around a computer at the moment, and you'd prefer to play on the go? id's got that covered too, making the iOS port of Wolfenstein 3D free for today only (the iTunes page still reflects a $1.99 price as of this writing, but Bethesda says it'll flip to free "later today").
Or maybe you've already played Wolf 3D more than you'll ever need to? Creator John Carmack recorded a director commentary aimed at superfans of the series, which we've embedded just below the break. Let us know if he talks about rockets at all!