At the time the Cortex Plus Hackers' Guide had come out there were three major published games using Cortex Plus; Smallville, Leverage, Marvel Heroic Roleplaying - but the license for both Smallville and Marvel Heroic expired at the same time (Firefly has now been added to the ranks). The Cortex Plus Hackers guide presents generic rules for all three games, plus handfuls of hacks for each of them, showing how to adapt each of the three games to various settings.

The system (or more accurately the family of systems) is fast, light and incredibly evocative as long as the GM is good at thinking under pressure and coming up with random complications at a pacing set by the system. The biggest weakness of the system (or rather systems) are that they are incredibly swingy.

Firefly vs Serenity - because there are plenty of good reviews here but none go into the detail of the two systems. Production values and research are excellent for both, of course, and if you want a coffee table book then both work.

The obvious is that they are two separate licenses. If it was in the series but not the film there will be no official stats in Serenity. If it was in the film but not the series there will be none in Firefly. (Because MWP owns the system there are some dual-statted adventures). Less obvious is that Cortex and Cortex Plus are very different systems.

Serenity is a solid traditional RPG. One where the GM is in control of almost everything, and one where there's sufficient grit that leads dying occasionally is expected (which of course matches the film but not the series). Combat is moderately long with tactics and explicit rules for taking cover and the whole thing is if anything a bit grittier than the Serenity movie. Weapons are handled by stats such as range and reloading. Ultimately it's a fairly consistent generic system with a tone that's pretty good for the movie.

If Serenity is a stately waltz, Firefly normally starts with some idiot (normally a PC) setting fire to the third bar and the whole thing turning into a jam session. Things don't go smooth, and even GM plans should be cooked rare because they will be derailed. Scene assets and complications, frequently introduced by the players, are almost as important as the skill of the acting PC. That said, the system is designed to handle any wacky plans the players can think up to the point that making The Destroyer into something made of marshmallow is not a problem (seriously, Firefly is a near perfect system for 80s comedies like Ghostbusters or Police Academy or even more modern comedies like Guardians of the Galaxy where it's blatantly obvious the GM doesn't know what's going on although it does work for more serious games). PC death doesn't often happen except by consent in Firefly - but there are so many other ways for e.g. Saffron to leave Mal wishing he'd never met her with Complications (mechanical representations of in game problems) that this rarely matters. Combat is short and sweet, over in only a few die rolls that use the same system as everything else and weapons are handled with a single number each (with Vera being really effective, although Jayne's pretty good with any gun).

Which is better? What do you want? Something planned out in detail? Or high octane mayhem with everything going wrong and the wheels always on the verge of falling off the wagon.

Me? I prefer Firefly (both series and game). But they are different games, reflecting the different tone between the series and the film.

This is a fully playable demo rather than the finished product, and as such is missing quite a number of things, but is more than enough to play. So be warned - the full game will have more content and this is more a very functional preview or a lite version. It's wonderfully presented (as anyone who knows any MWP games will know) and very effective.

It is also the second system for running in the Firefly universe, with the first being Margaret Weis Productions' Serenity using the Cortex system. The two systems are very similar, both light and fast flowing - and haveIMO too much volatility with the inept having decent chances to beat the experts.

Ultimately, however, the difference between the two systems is one of emphasis - Firefly ows a lot to the previous (and excellent) Leverage system for which MWP subcontracted Evil Hat (Fate Core, Spirit of the Century, Dresden Files). And whereas Serenity put its focus on questions like "You are Ianara firing a bow from behind a rock at goons hiding behind pillars. How much less damage do you do than Jayne with Vera?", Firefly puts its focus on questions like "You are Jayne and have just punched someone out for making fun of your cunnin' hat. How much trouble have you just created for the rest of the crew to deal with later?"

And that second type of question is, to me, the core of the 'Verse. Combine that with a couple of excellent and fun (if very slightly railroady) adventures (one being intrigue heavy and involving weddings and popular princesses, and the other being a romp of a race to rescue orphans) and you have an excellent game.