Alyse:
I have the public beta playtest draft, but have not really done more than skimmed it. How does the third edition differ from the first and second? (Not sure which of the previous editions I've read, sorry.)
In terms of mechanics, quite a bit - it's an entirely new system, designed for action-movie style action rather than the heavy simulationist bent of the prior editions (well, edition - the rules in 1st and 2nd edition Mutant Chronicles are basically the same - 2nd edition was more a reprint/revised edition than a completely new version of the game).
The core mechanic is simple: a test requires that you roll two or more d20s, and compare each to a target number (determined by the character's attributes and skills). Each d20 that rolls equal to or less than the target number scores one success. The difficulty of the test is the number of successes required. Rolling more successes than you need for a test grants you Momentum (one Momentum for each surplus success), which can be spent immediately to improve the action you've taken (inflict more damage with an attack, for example), or saved to help yourself or another member of the group in a later test.
It gets a little more nuanced when you add in the skills system, and the ways in which you buy extra d20s for a test (2d20 is the default).
Skills are rated in two ways - Expertise, and Focus. Both are rated from 1-3, or 1-5 for three 'Signature' skills on each character. Expertise is a flat bonus to a character's Attribute scores for tests against that skill. Focus is the natural value on each d20 that scores two successes. For example, if a character has Coordination 9, Ranged Weapons Expertise +2 and Ranged Weapons Focus 2, he needs an 11 or less on each d20, and any rolls of 1 or 2 score two successes instead of one.
Buying extra d20s for a test comes from a few sources. Some talents allow bonus dice, as do certain actions (the exploit weakness action in combat grants +2d20 on an attack roll), and the expenditure of resources like Reloads (each Reload spent on an attack adds +d20 to that attack roll). The most common way, however, is by paying Dark Symmetry Points into the GM's pool (Dark Symmetry Points are the GM's resource, for things like acting out of order or fuelling NPC special abilities). Each Dark Symmetry Point paid to the GM grants +d20, to a maximum of +3d20.