While highly destructible buildings and physics are the draw card, this is a solid action game all around.
While Red Faction is essentially a third-person shooter with a cover system, the open-ended map, mission structure and destructible environments make it feel more like a sandbox adventure game. The world is seperated into different districts, and your goal is to liberate each of these districts. To do that, you need to reduce the EDF's control of that district, which you can do by completing missions, or destroying important buildings. Once a district is liberated, then missions are opened up in the next district. Missions are marked on your map, and selecting a mission on the map gives you an onscreen indicator of how to reach it throuhgout the mountain ranges that make up part of the landscape. Vehicles play a big part in Red Faction Guerilla, and you will need them to reach you destinations quickly, take rescued hostages back to safehouses, or take marked vehicles back to a safehouse. On top of that, vehicles can be a great way of ramming buildings.
Destroying stuff is far and away the greatest thing about Red Faction, and the physics are excellent. There are no canned animations here; every building is made up of its individual panels, girders, door frames, support beams etc. So if you take out the support beams of a building with your trusty sledgehammer, it will be much more likely to fall over. Further to this, buildings don't always fall straight over. Sometimes pieces will fall off one by one, and that increased instability causes another to fall, until several seconds later there simply isn't enough to hold it together. Different parts of buildings have different toughness, so targeting the right areas really helps take them down faster. While you are given a purpose to destroy EDF buildings (reducing their control) you won't need much motivation because it is so much fun.
Of course, the EDF aren't happy about you destroying their buildings. If there is no reason for them to be chasing you, you can pass them on the road without them noticing, but once you bring attention to yourself, they will start gunning for you. It is during these instances that you will find you are as destructible as the buildings you destroy. The enemies can take you out in short order, but this feels like it is by design; hit and run tactics are a better option, as each time you die you respawn at a Safe House which can be a while away from your current target. While you can remain holed up in a building, enemies continue to stream to your location once they are on alert, and it can sometimes be tough to make it out alive, especially as you start running out of ammo, which usually doesn't take long.
During the course of the games as you unlock more missions, more potential weapons or abilities will be unlocked. Even if they are unlocked, you will still need to purchase them with the games currency, salvage. Salvage can be earned by completing missions, or picking it up from destroyed buildings or vehicles. There is a nice range of weapons, each offering their own perks, and most can also be upgraded. You can only hold 3 weapons on top of your sledgehammer, so you have to be strategic about what you bring in to battle. 3 slots full of explosives gives you plenty of options to destroy buildings, but if you come up against EDF soldiers, you might find things a bit more difficult. While a few weapons overlap, there is little redundancy and most of the weapons have their own uses. That said you are likely to find your favourites and stick with them for the most part, unless a missions seems to dictate switching things up.
As well as the regular vehicles, there are also some walkers which are like mechs. There are a few different varieties, but these are only available in specific missions. I found most of them too cumbersome to be as enjoyable as the rest of the game, but it was still fun. Later in the game a new gameplay type opens up, offering you the chance to destroy EDF forces using a sattelite. Again this isn't as enjoyable as the rest of the game, but it does add to the variety. On the standard difficulty the game offers a reasonable challenge, though at time you may feel a little frustrated when you die without feeling like there was a way out. I also found the final mission difficult to the point that I turned down the difficulty after an hour of trying.
While I have not played the online portion of the game, there are some round robin modes where players take it in turns to get the highest score. Basic rounds have unlimited ammo and a time limit, but the more interesting modes limit your ammo and this gives it almost a puzzle like feel, as you try and figure out the best way to maximise destruction with as few shots as possible.
While the destruction physics are the stand out feature of Red Faction Guerilla, everything else about the game is solid. There can be a bit of background pop-in from time to time, and some rare physics glitches, but otherwise everything technical about the game also works well. With a campaign that can take you 20 hours if you explore all the side missions (and you will want to so you can unlock the best weapons and upgrades), liberating Mars is great fun.