Interface

Mass Effect employs the Manual interface for both the Xbox 360 console and the PC, though I'll focus on the Xbox, since I've not played the PC version. The controller layout for action gameplay is similar to Gears of War, though a bit more complex and a little more sluggish because they are not designed simply for tearing things into bloody pieces. You can use the D-pad to give your squad mates orders and the bumper buttons to switch/select weapons and use powers. The powers are the most awkward thing to control as a result of using only one button. This is unfortunate because the X button simply takes your weapons out, which can be done just as easily with either the right or left trigger. It's just a poorly utilized button, especially considering you need to use the inconveniently placed Back button to throw and detonate grenades. Overall, however, the shooting is really easy to get the hang of, especially for anyone who has played a shooter before or just turns the auto-targeting on and the difficulty to easy.
During combat you'll see the HUD, the heads-up interface, which is passive. It displays relevant information about Shepard and his allies like how much health and shields they have left, the commands your team is following, the minimap for navigation (which could use more detail), and how close Shepard's weapon is to overheating. There is no ammunition to worry about in Mass Effect. This is definitely a relief because combat is not the coolest part of the game for me by far. If you are engaged with any enemies, they're name, shield, and health data will appear at the top of the HUD when you lock on to them.
Mass Effect is not an extremely envelope-pushing game, however, one of it's key innovations is in its conversation system, which presents different options for dialogue in a circular formation that can easily be chosen by rotation of the right analogue stick. Rather than giving the full line of dialogue for the player to choose, the game presents a brief summary that Shepard will transform into his/her own words when selected. I've come to think of these short lines as the thoughts going through Shepard's mind at the time. This system makes selecting what you want to say so much easier than scrolling up or down and reading through long lines of dialogue, keeps the flow of the conversation realistic, and actually allows the player character to speak audibly! For even greater ease of use, the mean options are usually at around 5:00 on the clock-like configuration while the nice responses are around 2:00. More investigative choices are over at 9:00. The Persuade and Intimidate techniques can also be used with the wheel just like talking regularly except they appear in blue and red respectively. The one problem with talking through abbreviated lines is that sometimes the thought will differ slightly from what Shepard actually says and sometimes the thought is funnier than the actual line. That is what makes me think the dialogue options represent thoughts. We humans often have extreme emotions and impulses that are disguised by more mellow words. The best part about this new conversation system is that the characters actually act, emotionally and physically, during the dialogue portions of the game. You have no direct control over how Shepard follows your orders, he/she just does as you tell him/her, but it's a HUGE improvement over KotOR's stiff looking characters, repetitive gestures and motions, and fade outs whenever their was an implied action with no animation. This wheel system can also be used to control actions. Sometimes during a conversation, an option such as [Shoot Him] will appear and Shepard will comply if this is selected. Sometimes, the context of the thought is enough to get Shepard to take action. Other times, the wheel is only used for actions and not conversation, as seen below. In addition to the HUD, the occasional cinematics are another passive interface that exists to tell Mass Effect's story. Most of the plot is laid out in front of Shepard's and the player's eyes during the above-mentioned conversation sequences, but even the Spectre can't be everywhere at once. After the first mission, for example, a cutscene shows Saren getting all agitated about one of his plans being foiled. It reveals a bit of his character and evil plan that cannot be witnessed by the player character who is in a coma at the time. The character creation interface functions well. It is designed for precise detailing of your characters face. Changes to most of the sliders do not significantly change things and different preset structures form the basis for Shepard's face. However, it still allows for a very different face every time you play the game. One of my favorite features is the scar slider that provides you a selection of slashes and burns to make your Shepard into an unlucky soldier or gnarled veteran if you want. It's not hard to make a sexy character either, though rugged may be more realistic. My female version of Shepard was much too fine to be running around fighting aliens. Like most of the interfaces in the game, the player creation interface is active. Another example is the pause menu. There are a bunch of options available to the player here, including the Options menu, the Equipment management interface, the Codex (basically just a Galactic encyclopedia that completes itself as you advance), the progress Journal, the Squad screen, and the options to Load or Save a game. The "Options" menu has the basic audio, visual, and difficulty customization choices as well as some other related items. The Squad screen allows you to level up Shepard and your team. You can also access a Map from the pause menu, which permits you to see the constrained area in which the action is taking place. Along with this map comes a chart on a much larger scale, the Galaxy Map. This tool looks pretty cool as a floating hologram in your ship. It makes navigating the vast galaxy as easy as finding Waldo, even if it's a bit repetitive. You zoom in on star systems and then on planets, while the map calculates your Mass Relay route automatically. Getting a close up view of planets is interesting because every single one has its own description, even if you can't land on it. The only problem I had with the Galaxy Map was trying to zoom out. You're supposed to press X but my intuition kept telling me to press B, which exits the map. Then it has to load again if you want to go anywhere. As for the audio in Mass Effect, I would not consider it part of the interface. The only time it comes into gameplay is when your teammates constantly yell out "Shepard's been hit!" or "Enemy Sighted!" Other than that, the music and sounds really only serve to make the experience intense and dramatic and they are only of high quality during the cinematics and conversations.

Rules

Like many RPGs, one of Mass Effect's primary selling points is its freedom of choice, which translates to freedom from certain rules that may constrain more linear games. The player has the option to select how Commander Shepard will look for the duration of the game, what his/her back story is, and how he/she will react to situations, verbally or physically. The player is not even restricted to the world of the story. Even though the mission to stop Saren is the core part of the game, there are other planets the player can visit if he/she chooses. A strong effort is made to make the player feel as though they are in control of their destiny and that what he/she is doing is meaningful. The rules in Mass Effect are not based on achieving a high score or defeating another human player through mental or physical means, but rather accomplishing various objectives to eventually solve a mystery and defeat a villain. The goal is to have an emotional experience with the core story and the exploration of the galaxy.

1. Operational Rules: While there are a few sequences which must be completed quickly, defusing explosives before the timer runs out for example, Mass Effect has no overall time limit. Commander Shepard is free to go around the galaxy at his leisure. The only thing compelling the player to finish the game is the emotional impact the game has. Of course, the galaxy won't really end if the player doesn't stay up late to beat the last level instead of taking care of it in the morning. Within the game, the physical rules are realistic to our universe with certain exceptions, such as the common inaccuracy of sound being able to travel through the vacuum of deep space when ships fly through it (though the dogfights would be a lot less dramatic in silence). Also, the convenient discovery of Prothean technology and biotic powers allows the weapons, vehicles, abilities, and especially locations to be literally out of this world. Other than that, though, physics [attempt to] behave realistically. Gravity holds you to surfaces and environmental factors like lava incinerate you while you explore these surfaces, just like in real life! Sadly, realistic rules do not always apply to the NPCs. The civilians standing around cannot be fired upon and if you want to shut Liara up, you'll need to find a way past her invincible shield that absorbs every projectile you throw at her. Programming outcomes for these actions into the game would be nearly impossible though. The possibilities would be endless. The consequences that have been put into the game involve certain gameplay penalties or rewards and what emotions the player feels in response the situations that arise, the NPCs that die, the relationships that form, the musical score, and the gameplay itself. It is difficult to quantify these and they will be different for every player. On the other hand, more standard processes, like the death of Commander Shepard, will probably happen for everyone. If he/she absorbs enough high velocity particles to drain your shield and life bar, the Commander will die. This is only temporary of course. The player has the power to travel back through time using the Save and Load features and can try sections of the game until he/she can complete them.
Sources of damage for Commander Shepard come from the assault weapons of his antagonists, melee attacks from less sophisticated creatures, or even a suicidal grenade thrown by the player. On the other hand, if you make your enemies absorb enough high velocity particles to kill them all, and can manage to find solutions to the fairly simple puzzles on each planet, you will eventually win.

2. Constitutive Rules: Reducing Mass Effect to its most basic mathematical structure is not recommended because it severely cuts down on the immersion you feel. When the player becomes aware that they are playing a game, the constitutive rules, the underlying structures that make regulate the game, are noticeable. Even though conversations are a big improvement over Elder Scrolls IV: Oblivion and KotOR, you can still tell they are scripted. The construction beneath the story are fairly visible whenever a line of dialogue or a motion (like the fist into the palm) is repeated. Other obvious repetition can be found on most of the side quest planets. They are mostly just very similar mountainous regions with different textures and environmental effects pasted over them.
Using elevators to get between floors is another annoyance that is necessary for the game to disguise load times. It is preferable to a blank screen, especially when an interesting dialogue accompanies the ride, but there are just too many of them, especially on Noveria, where there are also no news flashes or conversations between your party members. Some of the rules exist to keep the game balanced and functional. For example, it might be prudent to take all of your allies and the marines from the Normandy with you to help in your battles but you can only have two NPCs with you at a time. Each character has his/her own skill so it is up to the player to decide how to balance his/her squad for maximum combat effectiveness.

3. Implicit Rules: Any of the gaming standards that Mass Effect conforms to could be considered "implicit rules." The basic controls, for example, should be familiar to most console gamers. They are written in the instruction manual and should the player need to refer to this, the control scheme would likely fall under "operational rules." It is also implicit that your actions will have consequences. The game is basically a life simulation, even though the life is outlandish and in extreme circumstances, and in life, actions have reactions.

Characters

THE HERO:

Commander Shepard
Commander [John, Jane, Jack, Max, Elizabeth, etc.] Shepard is the player's avatar, that is he or she is the sole player-controlled character in Mass Effect. His or her gender is really only relevant to the optional, but meaningful romantic side quests. Shepard clearly fills the role of the classic "hero" archetype and is the game's protagonist. Like all of the characters in Mass Effect, Shepard fits the "fantasy" character type. The Commander walks the walk of a proud soldier to which either a brutish or heroic personality can be applied. This personality is up to the player to create. Through conversations and actions the player can make Shepard into a chivalrous hero or ruthless agent. As a good guy/girl, Shepard is who I want him/her to be: generally nice, but not ridiculously benevolent. Shepard is a soldier, not Santa Clause. Like I mentioned previously, being a douche bag is not as fun as it could be. He's mean without taking a lot of action and often for no good reason. This is a little at odds with his mission to save the galaxy. Still, it's humorous to punch annoying civilians on occasion and it's refreshing to just order your team to start shooting instead of wasting time being diplomatic. Too often unfortunately, the choices you make are followed by very similar consequences. There is repeatedly no difference between outcomes other than the way the NPCs react emotionally. These reactions are quite evocative, as I said before, they often make the difference between choosing good over evil. However it would be nice if there were heavier repercussions to your choices a little more often, because when the choices do matter, the game excels.
One of the problems with Shepard's character arc is that the character does not really transform or even gain much enlightenment. It's partially because the player has a great deal of control over Shepard's thought and he/she is not likely to go through any significant life changes or experience any epiphanies while playing Mass Effect. Therefore, the player's choices will probably remain consistent throughout the story. Also, the story doesn't leave much room for the character to advance. He/She starts out as an experienced soldier and ends the game the same way. Sure, Shepard's skills increase as he/she gets more experience but this is not tied to the story at all and the Commander doesn't learn any significant new abilities. Early in the game, Shepard does at least attain the unrestricted rank of Spectre, which means he can go around doing pretty much whatever he wants to get the job done. This doesn't really affect his character as much as it affects his rights though. Once again, I feel the need to bring up KotOR because of how the protagonist in that game goes through the arc of starting off as a foot soldier, then learning to use the Force and becoming a Jedi, and finally becoming the savior of the galaxy. The growth of your character made it feel like more of a journey than just a mission. One more thing that would add depth to Shepard is some kind of personal flaw. The story isn't a tragedy so it isn't a necessary device but it seems a bit strange how he never really makes a mistake. Shepard's advantages over KotOR's hero come in the form of his/her definable background, very variable appearance, audible voice, and even his/her authoritative position. While it doesn't give the Spectre much room to change, it does give you a lot of freedom and the respect of most people you meet across the galaxy. This story is more immediate than KotOR's and any time spent learning lessons could slow down the pace too much. Controlling Shepard's thoughts and feelings is also quite intuitive and his/her resulting lines are fairly well-written. The Commander's "the only kind of person who can protect the galaxy," no matter what you make of him/her.

EDIT 2/21/09 - The teaser trailer for Mass Effect 2 is telling us that Commander Shepard has been Killed In Action! WTF? Will we be playing as someone else? I just realized now that I'll really miss Shepard if he/she is dead.

ALLIES:

Lt. Kaidan Alenko
The lieutenant with biotic powers is the first member of your core party you meet as he is already a member of your crew. If you choose to play as a female, you can form a romantic relationship with him. I cannot attest to his sex appeal, but women (or those claiming to be women) on YouTube seem to like him. He's pretty cool, though not quite as interesting as Carth Onasi of KotOR, who shares his voice. He doesn't have his own side quest other than the relationship with Shepard but his backstory is still interesting. He lends Shepard his moral support when the chips are down and his ability to unleash "dark energy" and tech powers is useful in combat. On the whole, he's a good, dependable guy and it's a sad thing to choose to let him die on Virmire. On the other hand, it's harder (for me at least) to sacrifice the other possible candidate.

Gunnery Chief Ashley Williams
Here we have, in my opinion the hottest member of the crew, though that's not saying much considering her competition of various species. She is hot anyhow, with a fiery and frequently funny personality to match. I really like Ashley and I found it easy to make Shepard like her too, even though their possible romantic interest in each other has no clear starting point. She's a skilled soldier who specializes in weapons and is always up for a fight. She is not a perfect person, with some prejudice against other species and a headstrong attitude, but her flaws make her more human. Either she or Kaidan must die on Virmire and it seems natural to save Ashley if you're a good guy and save Kaidan if you're a good girl. If you're a renegade, it probably doesn't matter because you'll likely have spurned any romantic advances. Either way, it's a sad moment. If you do fall in love with Ashley and rescue her, you'll have the option (as you do for any of the romances) to participate in a tastefully choreographed sexual encounter, which includes a brief, controversial shot of her polygonal ass. It seems ridiculous for FOX News to bitch about this when the Internet and games like Grand Theft Auto exist, but as usual, nudity is more treacherous than bloody violence against civilians and police officers. Anyway, Ashley's awesome.

Garrus Vakarian
This guy is like a space police officer. He has a really neat introduction where he pops some stupid hostage taker in the dome from twenty feet away, but after that he has no more slick signature moves. He does have a character arc, though. With Shepard's influence, Garrus can change his views on his methods for getting things done. He starts off with a fairly logical but merciless point of view. He is in favor of execution and justice. If you're a nice guy/girl you can convince him to "do things right or [not do] them at all." This arc ties into his side quest which involves an organ-harvesting mad scientist. It would be nice to see the rest of the characters have their own arcs, especially if the player has the power to influence them. Garrus is a decent addition to the party, though his analytical tone gets a bit dry sometimes. A few more of those nice moves would have made him more interesting.

Tali'Zhora nar Rayya
Tali is sort of the kid of the ship. I don't know how old she's supposed to be but that's just what she seems like; a little homesick, fascinated by new sights, and inexperienced. I expected that she would be lame at first, but I soon grew to like her because of the enthusiasm conveyed by her high, excited voice and her commitment to the mission. In addition to being an ally to Shepard, she also takes the role of "herald" by providing information that changes the course of the plot and sets Shepard and his team in a new direction. She's quite useful for cracking computers and locked doors and also handy with grenades.

Urdnot Wrex
This krogan mercenary is probably the most badass, well-written character in Mass Effect. His dialogue is short and to the point and all delivered in an wonderfully rough, gravely voice. He's often quite humorous too, with lines like, "Anyone who fights us is either stupid or on Saren's payroll. Killing the latter is business. Killing the former is a favor to the universe." He's also the only one who has the balls (4 of them according to Garrus) to stand up to Shepard. Wrex has a tough exterior but you can tell there's a lot more to him than mindless brute force. He has an interesting past and, like Garrus and Tali, a side quest. I found this quest to be a bit disappointing for such a great character because it just seems that fetching a family heirloom is beneath this warrior. Plus, there are no cinematics for it, a common annoyance in Mass Effect's side quests. At one point in the game, you can choose to shoot him if you really want to. Yet even playing as a villain, I keep him alive. He's just too cool to kill. Besides, you'll want him by your side in later battles, throwing synthetics around with his biotic powers and blasting them with his shotgun, growling, "Give me something to kill!"

Liara T'Soni
If I wanted to be mean, I could call her the opposite of Wrex. Dr. T'Soni is the third and last romancable character and can be wooed by either a male or female Commander. Ostensibly this is because her species has only one gender and they can meld their minds with other life forms but part of me suspects the designers knew a "lesbian" sex scene would be a selling point of the game for some people. She will always be the one of the points in the potential love triangle between Shepard, Ashley/Kaidan, and her. Despite being of another species, Liara is easily the least interesting option for courtship and possibly in the entire party of key characters. She has trouble knowing when to shut up and her voice is a bit monotonous. Some of her explanations seem as long-winded as my descriptions of character and story (but not even close to the melodramatic monologues found in Metal Gear Solid 4: Guns of the Patriots). I still feel for her though, especially after she has to help kill her own mother, who works for Saren. She devotes all her skill points into using biotic powers, which is occasionally helpful when the fighting starts. Still, she is probably the least of Shepard's six core allies.

THE MENTOR:

Captain David Anderson
Eloquently voiced by Keith David, Captain Anderson serves as Shepard's primary mentor, though most of the mentoring happened before the game begins. Early in the game, he talks the Commander through some objectives and gives advice. Though you can't tell by his poorly-designed uniform, he's actually a badass, and is instrumental in the success of Shepard's mission. He represents what Shepard could become if he chooses the path of the paragon, the good guy. He has a balanced personality and is an able leader. He has a past with the villain, Saren, which you can learn the details of if you read the prequel novel to Mass Effect.

THE SHADOW:

Saren Arterius
I would have to describe this bad guy as an "exaggerated" antagonist because to be realistic, I think his species would have to exist. Also, he is part machine, rides around on a hovering pad that fires rockets, and seeks to bring unstoppable, genocidal robots to power. Saren is a sinister villain that needs a little more development to be seen as truly frightening. Even though he shoots one of the minor good guys on the first mission, his brutality is hardly ever witnessed, just talked about. I think it would have been helpful motivation for the player if Saren's evil doings were presented more clearly. Comprehensively, he is a pretty good bad guy; he looks great and sounds great, but he talks to much and what he says is sort of noncommittal. It is too easy to turn him away from his evil scheme at the end of the game so I recommend taking the quickest way through the conversation and just blasting him. Luckily, his hesitation and lack of zeal can be explained by the evil Reaper controlling him. This giant machine is the real threat to the galaxy and it's freaking huge and powerful. The idea that there are a whole bunch of them is more menacing than Saren ever is. It's okay though. Saren's just a bit more complex than you might expect.

GUARDIANS:

The Geth and others
These synthetic AIs work for Saren because they worship the Reapers as gods. They are just tools, but they have an interesting past and personalities, something I wasn't expecting from droids. They basically come in many forms, all of which try to kill you and your party members. They are the guardians of Mass Effect, along with some other species and strange creatures that attempt to prevent Commander Shepard and his allies from saving the galaxy.