For game design I have seen "Illusion of Choice" used in two main ways.

1. The game lays things out such that it looks like the player is making a choice. A or B. However, neither option actually changes anything, and the player will not be impacted in a notable way. Eliminating one of the 'choices', or replacing it with a coin toss, would not actually impact anything. To me I mostly see this as adding flavour and cosmetic options, which make the game feel more rounded and interesting, but can feel 'cheap' if not handled well. (ie, Deus Ex: Human Revolution end was cheapened in my view, as all the choices you make eventually lead you to basically a single choice node at the end, but don't actually have an impact.)

2. The "win or death" choice. To me this is just bad design. Sure, you "can" play as the necromancer character who relies purely on minions to protect your character and deal damage, but if you ignore their buff/debuff skill tree and the direct attack skills, then you will be totally steamrolled by mid game and will be forced to restart from the beginning because the choices you made were completely unworkable. Or you "can" choose to use the shotgun instead of the sword, but you won't be able to complete the game with it because you'll run out of ammo.

Win or Death is basically a single line or narrow line of choices that lead to victory and additional choices that all lead to defeat, but the game leads you to suggest they are all equally valid. These have to be VERY carefully watched for. They can work in a game, but you risk annoying the player.

It is also related to what I refer to as a precognition door choice. You present the user with two or more doors. Behind one is treasure, and behind the other is a horde of angry shot gun wielding clowns who will near instantly kill you no matter what you do after that door is opened. During your first play through they are both equally valid choices, but the player is not given any information on that 'choice', and therefore is forced to pick at random. The player is then punished for being stupid and not picking the 'one and only correct' door, and must restart/reload, from where they can then select the 'correct' option only after they have already viewed the outcome. To me these are simply annoying and frustrating, and make for an easy reason for me to hit the power switch and just go outside or something.

I think, that the term Illusion of Choice is not clearly defined and different game designer will interpret it differently.

IMHO: from a game design point of view, or more clearly said, from a game mechanism point of view (skins, customization,item collection etc. are not really game mechanism), the illusion of choice is a choice which seems to be meaningful at first, but is meaningless at the end.

I can think of this example:

Take a standard RPG, you have Hp and Armor as combat attributes. The player have the choice to either invest some gold into pimping his HP (special training) or into buying better armor. At first it seems like a real choice, make a bear like barbarian with lot of hp or a knight with less hp and lot of armor.

Now, if you look under the hood, you see that armor have the following effect on hp:

new_hp = hp - damage* (1/(1+armor*0.01))
<=>
new_hp / (1/(1+armor*0.01)) =hp / (1/(1+armor*0.01)) - damage
<=>
new_hp * (1+armor*0.01) = hp*(1+armor*0.01)-damage

That is, 1pt of armor increases the hp for 1%, therefor at the end it doesn't matter if you buy hp or armor, because your armor is just an other more obfuscated, way, to increase your hp (at the end the player just buy the most cost efficiently solution to increase this hp => no choice).

Btw, LoL is doing it this way, and what looks like pointless game design at first, it gives the player an additional option to play the game in a different way (the way of imaginating the game universe) without playing the game in a different way (the way of the game mechanism).

I have to mention, that LoL have other ways of making the choise of hp and armor meaningful (different damage types ignore armor, hp is more expensive etc.), but without this additional benefiits it would be nice example of the illusion of choice.

Every time I try to imagine an illusion of choice in the more popular games I play(Rift, League of Legends, Wildstar) they still seem to boil down to people deciding on a preference. To me, that seems like it makes the choice meaningful. When someone decides on a race for their new MMO character, even if race plays virtually no role in the game itself(instanced PVP randomized without thought to faction, cross-faction trade, guilds, communication, etc), it still comes down to someone deciding which race is aesthetically pleasing to them, which feels like a meaningful choice.

These are really two different things. Traditional games (think of chess etc.) are more about game mechanism. In this case a choice should have a meaningful effect. In modern games lot of other human aspects are integrated, like the tentency to collect stuff (CCG, diablo), to pimp yourself, your garden or your car (avatar customization), which aren't really game mechanism. Always view this stuff as additional value to make your game more attractive to a broader audience, but at the end it doesn't matter and there is no real choice, not even an illusion of choice.

When someone chooses to buy a new champion with RP(cash currency) instead of IP(earned in-game currency) in League of Legends, even though in the end it doesn't really matter, it still feels like that player is making a conscious decision to use their IP on something else.

Well, this i a business choice and this choice has not a lot to do with the game (thought the IP itself is a ingame-progression system), therefor RP is more like a cheat than a game mechanism.

I can think of this example:

Take a standard RPG, you have Hp and Armor as combat attributes. The player have the choice to either invest some gold into pimping his HP (special training) or into buying better armor. At first it seems like a real choice, make a bear like barbarian with lot of hp or a knight with less hp and lot of armor.

Now, if you look under the hood, you see that armor have the following effect on hp:

new_hp = hp - damage* (1/(1+armor*0.01))
<=>
new_hp / (1/(1+armor*0.01)) =hp / (1/(1+armor*0.01)) - damage
<=>
new_hp * (1+armor*0.01) = hp*(1+armor*0.01)-damage

That is, 1pt of armor increases the hp for 1%, therefor at the end it doesn't matter if you buy hp or armor, because your armor is just an other more obfuscated, way, to increase your hp (at the end the player just buy the most cost efficiently solution to increase this hp => no choice).

The mechanical difference between HP and DEF doesn't seem to matter per attack, but it does matter a lot when you take into account frequency of attacks (whether from multiple enemies or enemies using quicker attacks). The relative benefit of HP and DEF enhancements will therefore vary situationally: assuming HP and DEF costs are balanced according to the average situation, then in situations where enemies make FEWER attacks than usual, HP enhancement is a better value, and in situations where enemies make MORE attacks than usual, DEF enhancement is a better value.

2. The "win or death" choice. To me this is just bad design. Sure, you "can" play as the necromancer character who relies purely on minions to protect your character and deal damage, but if you ignore their buff/debuff skill tree and the direct attack skills, then you will be totally steamrolled by mid game and will be forced to restart from the beginning because the choices you made were completely unworkable. Or you "can" choose to use the shotgun instead of the sword, but you won't be able to complete the game with it because you'll run out of ammo.

Win or Death is basically a single line or narrow line of choices that lead to victory and additional choices that all lead to defeat, but the game leads you to suggest they are all equally valid. These have to be VERY carefully watched for. They can work in a game, but you risk annoying the player.

I don't see this exactly as a "Illusion of Choice". I agree with the first one, mostly noticed in adventure games in my opinion (like most of the Legend Of Zelda franchise). But, this one, i think that's actually an unbalanced game, more than "Illusion of Choice". It merely depends on what was the intention of the game designers, if it was to truly make an "easy way" or an "hard way", or simply they weren't able to make the classes "equally playable". Sometimes, this can't even be done, where some ways just needs more gaming mechanics, like using the "Unarmed" skill on Fallout 3 or Fallout New Vegas, it's hard as hell.

Using this in League of Legends, for example. Sure, the game have more than one hundred playable characters with different skills, and they try to make it every single one playable, still i'm not sure if they intently make "powerful champions" and left the other ones used, or they just aren't able to make all of them playable. And, still, there's at least 1 patch per month, changing champions mechanics and skills power trying to make it balanced to the game.

I think that the worst problem that "win or death" causes it's the feeling of losing time. For example, when you spend hours on an MMORPG trying to improve your "miner skill", and when it's almost at maximum, you discovers that it's just pointless. You gonna through all this suffering to finally realizes that what you were doing was a complete waste of time.

It is also related to what I refer to as a precognition door choice. You present the user with two or more doors. Behind one is treasure, and behind the other is a horde of angry shot gun wielding clowns who will near instantly kill you no matter what you do after that door is opened. During your first play through they are both equally valid choices, but the player is not given any information on that 'choice', and therefore is forced to pick at random. The player is then punished for being stupid and not picking the 'one and only correct' door, and must restart/reload, from where they can then select the 'correct' option only after they have already viewed the outcome. To me these are simply annoying and frustrating, and make for an easy reason for me to hit the power switch and just go outside or something.

I don't exatcly think this as a problem. Yeah, sure, the situation you presented is completely pointless. You're like having fun killing things with a shotgun, than saves, than see yourself with the two doors and only one opportunity to choice, which one leads to death and the other one to eternal glory, and if you choose death, you just reload and now choose the right door. This situation, and only itself, is pointless. But, for example, imagine a game like Dark Soul, a game which challenge is at maximum, dying is so freakin bad, and bad choices have fuckin importants feedbacks. That door, with clowns that will kill you, sure will be effective. It won't be like "oh great, now i have to reload and choose the right door". It will be like "FUCKIN LORD I JUST DIED? WHY THE FUCK DID THAT HAPPENED?". Yeah, this reaction can be good or bad (if you want to make a game where the player will almost give up 99% time, this will be just great).

The situation itself can be completely pointless, but combined with other components, can be a really nice feature.

For me, the worst about choices, it's when your choice is completely meaningless. I mean, not illusional meaningless, when it's really just waste of time. For example, recently i tried to play Final Fantasy XIV a Realm Reborn, and when i'm creating my avatar, styling it as my unique avatar, there's a moment when i have to decide which god do my character believes in, and what the birthday of my character (both of them are from the universe of ff xiv). But this just affects NOTHING. Really, it doesn't make a fuckin change all along the world. It doesn't give you buffs or nerfs, it doesn't give you nothing. You're just there trying to decide something you won't even will use. And you won't even remember. Sure, the color of your hair you will be staring at least forever, but there is no point in saying that you were born in "the 27th sun of the 4th Umbral Moon". Really.

Imagine a choose-your-own-adventure story where multiple options led to the same page in the end.

Sounds like the Time Machine series I used to read as a kid.

Bonus, scroll to the bottom of that link to get "maps" of how the books were laid out.

Illusion of choice? Not really. It's educational!