Sliding Scale of Linearity vs. Openness
Some Video Games
are linear, forcing you to follow one set path throughout the whole game. Other games are more open, allowing you to choose how you progress to your goal. Some games are are even more open than that, giving you a wide open world to explore at your leisure. Most Action
games fall somewhere in this spectrum of linearity and openness; this scale exists to catalog exactly where they fall.
The Sliding Scale of Linearity vs. Openness is comprised of six categories for ranking how linear or open a game is. The lower on the scale a game is, the more No Sidepaths, No Exploration, No Freedom
it is; the higher on the scale a game is, the more Wide Open Sandbox
it is. Platform Games
will usually rank low on the scale (by design), while Role Playing Games
will usually rank high on the scale (by convention).
The most important factor in determining where a game lies on this scale is the game world itself. A game that limits you to one path will rank lower on the scale than a game that presents an open world and lets you decide how you are going to get to your objective. The objectives themselves are also important in determining a game's place on the scale. A game with a set story progression and one goal or a linear series of goals that get you from the beginning to the end will rank lower than a game with many Side Quests
or a game with multiple ways to progress through the main story. A game can still rank relatively high on the scale with few side quests if it presents you with many missions that are required to complete the main story line and lets you decide how/in what order you will accomplish them. The way the story is set up, however, will usually be influenced by how linear or open the game is, not the other way around.
- The game follows a linear narrative, as well as a largely linear pattern with how you move between levels and/or within the levels themselves. Any attempts at exploration will be inconsequential if not outright fruitless. There might be secret warps to later stages, but any bonus stages will be entered automatically. Rail Shooters are this level taken to the most extreme. Auto Scrolling Levels may be present. Games that fall into this category have become more and more rare with the passage of time. The majority of cinematic shooters fall into this category though.
- Though games at this level will still be largely linear in their design, you will have some choice in how you progress. You may be given a choice between two paths that take to you to the end of the level, or you may find a bonus level on the side that gives some reward before plopping you back on the main progression path. Exploration may result in some interesting discoveries. Many old-school first-person shooters fall into this category.
- Overall progression becomes less linear at this level. While levels themselves will still have a "get from point A to point B" feel, you will have many options in how you get from point A to point B. Backtracking will now be allowed, even if only to allow you to replay levels that you liked; whether the levels change from your initial trip through will vary from game to game. There is still a central narrative, of course, and these games are still on the more linear side of things, but they will not be constrictingly linear. Side Quests may be present, but will not feature prominently.
- We now get to the more Metroid Vania type of games. These games will likely allow you to explore and do side quests, but they will still want you to put the storyline first. Exploration will be encouraged, but controlled, with more of the game world opening up to you as you play. Games at this level will frequently play out such that you won't be able to explore the world or deviate from the main storyline at all in the beginning, but the whole world will be open to you by the end. Games can also fall into this level if the whole world is open to you from early on, but there's little reason to explore it other than to see the sights, and thus the main storyline will still be your primary concern.
- Open-world Role Playing Games. Games at this level will have plenty Side Quests and a very open world. (Some will still open up more of the world as you progress along the main storyline, but from the beginning, you will feel like you have a wide world to explore.) The main storyline may still be emphasized over the side quests, but it's not unheard of for games at this level to emphasize both equally. The central narrative itself may branch off into multiple paths, usually accompanied by Multiple Endings.
- Wide Open Sandbox games will be very de-emphasized and, if there even is a main storyline or central goal, it'll likely only comprise a very small part of the whole experience. You are free to do whatever you want in these games, and those at the highest end of the spectrum will have no limits on what you can do. There may be a plethora of Side Quests to keep you busy, or you may just need to make your own fun. Most MMORPG games fall into this category. Beware of sinking into the Quicksand Box.
See also the Sliding Scale of Content Density vs. Width
. Although there is a noticeable correlation between the openness of the game world (linearity of exploration) and the degree of Story Branching
in a game (linearity of plot), these are two separate scales.
- Most railshooters, although some provide branching paths that make them level two instead.
- Many side-scrolling platform games.
- Radiant Silvergun, except in arcade version where it is level 2.
- Wonderboy / Adventure Island 1: You go from left to right and there's no exploration except an occasional bonus stage.
- Tank Force. Enemies appear, kill enemies, repeat 35 more times, victory.
- Toki , a platformer taking place linearly in 6 stages.
- BIT.TRIP RUNNER where you move right and only jump, slide and block and kick on certain intervals.
- Though the style of gameplay in the Battletoads games tends to vary from level to level, the linearity in level design is very consistent.
- Cryostasis. The game follows a linear narrative and usually only a single path is available to take.
- Battlefield 3 single player campaign where the levels are getting from point A to B while regularly stopping to fight or have a cutscene.
- Homefront single player. You are hand-held throughout the entire game and have to do what must be done.
- Modern Warfare series single player campaigns also go to category 1 as there are are numerous setpieces and to make the game feel more dramatic, like a movie.
- Dishonoured: there are two main ways to complete any of the 9 missions (just murder the target or a Fate Worse than Death) which creates one of three endings and a handful of small tasks which grant you runes or open up new ways to neutralize the target, along with dozens of different ways to reach the target (rooftops, waterways, posses ion of animals, possessing people, sabotage or just simply murdering everyone) but each area can only be visited once and can lead to many a Guide Dang It moment if you missed a blue print for an upgrade or any of the dozens of collectables
- Conkers Bad Fur Day, unlike most Rare platform games, follows a mostly linear design and storyline, with very few collectibles (namely money and items that are specific to the chapters' objectives). However, during the first half of the game, it's still possible to leave a chapter's area and start another (indeed, Windy, Barn Boys, Bats Tower and Sloprano can be played this way, the only condition is that all of them have to be eventually completed). During the second half, which is set in nightime, the linearity dominates the progression completely, and the last three chapters (Spooky, It's War and Heist) have to be played in that order to finish the game (and once the very last one starts, it won't be possible to turn back).
- Final Fantasy XIII, whose linearity created a huge amount of controversy, not only about whether it was good or bad but whether it was true to the series.
- God of War
- Resident Evil 4
- The original Super Mario Bros. just barely made it to this level with its hidden bonus areas. Super Mario Bros. 3 almost exceeds it.
- Half-Life (justified in-story from the second game onwards as behind-the-scenes manipulation)
- By the same studio, Portal, insofar as many of the puzzles have multiple solutions and the player is often free to muck about for awhile.
- Visual Novels, if you consider them games, don't normally have more than different narratives depending on your selection. Some (called kinetic novels) are level 1, though.
- Ace Attorney
- Doom. You're supposed to collect keys and get to the exit, but there are also quite a few side areas which you can explore to find items, enemies to fight, or just out of curiosity what's there. Also, sometimes you have two or more ways of getting to the exit, and generally you can freely backtrack to early areas of the level. Custom maps often are less linear, sometimes qualifying as a 3.
- Glider PRO houses, on average. Bonus rooms and branching paths are common, but backtracking is often unrewarding or impossible. The mechanics of the game don't really allow for side quests.
- The Genesis and later modern Sonic the Hedgehog games which have multiple paths to complete the level, although the level layout is still linear.
- Flower. You go from point A to B, but you'll likely explore on your way.
- Eversion also falls to this category. It's rather linear, but levels often require lots of backtracking.
- Serious Sam series. Layout is usually very linear, but there are secrets to discover. Serious Sam II has the most linear paths, 3 has the least of them.
- Eternal Sonata: most attempts at exploration are thwarted by the characters.
- Bug!. There is only one end to a level, however, there is usually more than one path that Bug could take to get there. Bonus levels are also scattered around the area too.
- Far Cry. There are often many ways to tackle the level with a lot of paths to the goals.
- Soldier of Fortune series.
- Journey. Although it follows a linear narrative, the areas are often very large and exploration is often encouraged and rewarded.
- Battlefield: Bad Company contains a campaign that could be described as an adaptation of the series' large multiplayer maps for single player. Combined with the destructible environments that allowed you to could holes in walls you could move through, the game allowed the player to move freely and choose their plan of attack with a whole plethora of weapons, gadgets and vehicles to choose from. It's sequel was bitten with a "Call of Duty Competition" bug and narrowed the maps and limited the weapons and vehicles from whatever they give you at the time, but still kept an emphasis on destructible environments. Overall, the first game is at the top of the Level 2 scale while the second game is at the bottom of it.
- Star Fox Adventures. Like Conker's Bad Fur Day, and despite being an action-adventure game in the style of Zelda, it follows a mostly linear story progression, which is an oddity for a Rareware game. Backtracking is still allowed to collect Cheat Tokens, Energy Cells and even play a special sidequest in LightFoot Village (whose reward is still a Cheat Token). At one near-end point, though, the game will lock all main areas and the player only has the option to go forward in the events until the credits roll.
- Cave Story feels like a Metroidvania game, but is more linear than usual. The progression through the levels is limited by the plot and many levels are linear in design, but backtracking is rarely difficult and there are a bunch of rewarding side quests.
- Most Final Fantasy games. You have a handful of sidequests and might be able to visit a few places early, but it's all about the story. Though their non-linear last acts tend to be closer to level 4.
- Iji, where each level is a miniature Metroidvania.
- The Metal Gear Solid series, though close to a 2, makes it into this level. There aren't any side quests (at least, not in 1, 2, or 3), but exploring can lead to weapons, ammo, and supplies that can make your experience easier, and there are plenty of ways to navigate each room/area.
- In 3 there are what you might call sidequests in the form of destroying weapon and food supplies, also a few things like destroying the helicopter or killing The End early on.
- Sonic Adventure 2 (though the Chao raising minigame is decidedly level 6)
- Spyro the Dragon
- Super Mario World is still mostly linear, but does offer some options as to the routes you take. Many levels have two different exits which set you off on different paths along the map. Though all the road splits either eventually meet up again or lead to the bonus areas, you do have some choices how you progress through the map if you're not trying to find everything to get 100% Completion.
- The Tomb Raider series in general; levels throughout the series might only have one exit, but are frequently quite open beyond that. Some of the games are arguably closer to level 2 however; and others verge on Level 4.
- The MOTHER series, though the first game is a Level 4 verging on Level 5, as it only has three boss battles, including the Final Boss.
- Adventure Island IV. There are plenty of side routes although most of the level layout itself goes fairly linearly.
- Metroid: Other M (although edging towards a 2).
- In Blaster Master series, levels are opened in order, but there is a lot of backtracking to do and plenty of side areas.
- Half of the character's stories in SaGa Frontier fall into this category; Red, Emelia, Asellus, and T 260 G are all largely linear, with some exploration allowed, especially at the end of the game.
- Radiant Historia. The storyline is very linear and you can't reach anywhere the story doesn't specifically send you, but there are a downright ridiculous number of sidequests and backtracking (via Time Travel) is half the point of the game.
- Messiah. The game is overall linear, but there's a couple of side areas to find and the levels often let you run around more or less freely; there's also some backtracking. There also tend to be at least two paths to finish a task, even if the choice is usually between "get past stealthily" and "kill everyone".
- The Last Story is divided into chapters, and as such has expectantly a more linear progression than other RPGs, but some chapters are optional, and both Lazulis City and the castle are explorable extensively for sidequests (including the aforementioned optional chapters).
- Assassin's Creed
- The Banjo-Kazooie series
- Deus Ex: The "acts" are self-contained, and until you complete the task you can't advance to the next area, but within those acts you can explore and use stealth, hacking or shoot-em-up to complete your tasks. However, many of the more linear sections (especially later in the game) come closer to level 3.
- Dragon Age: Origins: You're locked into your beginning (one of six), the main storyline is always the most crucial thing, and while you can explore side quests concurrently with the main plot, certain areas of the game remain locked until certain points of the main story (often with a Beef Gate).
- Final Fantasy V. Lots of sidequests and exploration, solid main plot.
- Final Fantasy XII, verging on Level 5. There's probably more gameplay in the optional material than the main story, but you don't have to do any of it.
- The Harvest Moon series
- The Metroid series (with the exception of Metroid Fusion and Metroid Prime 3, which to an extent leans towards a 3), and Other M (which, as mentioned before, it's a 3 leaning towards a 2).
- No More Heroes has a wide open world, but there is little reason to explore it.
- Ōkami has some parts in which the player is locked by urgent events and cannot roam freely, but otherwise is very expansive and open-ended.
- Tales of Symphonia
- Skies of Arcadia
- The 3D Super Mario Bros. games. Super Mario Galaxy is a level 4 in terms of overall structure but most levels are Level 2, while Super Mario Sunshine and Super Mario 64 remain 4's throughout (and verge on 5 when enough of the game is opened up).
- Batman: Arkham Asylum. You work your way through a single linear storyline with only one sidequest (solving the 240 Riddler riddles, which is a borderline example of a sidequest) but you are free to travel anywhere on the island and use newer gadgets in older levels to discover new secrets. The actual story takes you back through at least four previously explored locations. A Metroid Vania title.
- Borderlands and its sequel. While fairly linear in progression of story missions, there are plenty of side quests to be completed whenever (as soon as available or even after you've beaten the main quest). And if DLCs are available, you can start their story quests immediately, even before finishing the main game!
- Seiklus. There is a main objective but you can start doing this from any end. There are few sidequests though.
- Chrono Trigger and Chrono Cross feature (multiple) worlds that you can easily explore and open up fairly quickly, with numerous optional sidequests and incentives to revisit old areas. In Chrono Trigger, you can fight the final boss at any time starting less than halfway through the game; in Chrono Cross, you can make numerous important decisions that affect which areas you will need to navigate, which characters join your party, and how various subplots are resolved. Both games feature Multiple Endings, though without using New Game+, they are implausible in Trigger and impossible in Cross.
- 1000 Amps. Eventually you'll get to the main branching hub and you'll start to can start beating each branch of the world from there.
- ARMA II. The majority of battles are not scripted, player needs to decide where to go and how to approach objectives etc.
- The Grand Theft Auto series
- The Legend of Zelda series (the later games, at least, with some variation).
- Final Fantasy II. Once you get the canoe you can go to any location on the planet except for Deist and the Black Mask Island and Palamecia, but be prepared for Beef Gates to curb stomp you back onto the plot.
- Legend of Mana. All of the 60 or so quests are optional but playing through them rewards you with artifacts that you choose where to place on the Overworld Not to Scale to create the Adventure Towns. There are very few cues to determine where to go or who to talk to to progress, leading to long sessions of wandering around the world looking for what to do next. While highly addicting due to its incredible amount of customization options and details, the lack of a strong central narrative to tie the 3 main story arcs together was criticized.
- The Dead Rising series
- The Escape Velocity series
- The Fallout series is highly open, and you can go pretty much anywhere right from the start. Now, that does not mean that you'll be able to survive wherever you go; except in Fallout 3, Level Scaling is absolutely not in effect, and threat placement means that if you go to some locations before you're ready to handle the enemies there, you'll be gecko chow in short order. In Fallout: New Vegas, this is the main incentive keeping you from rushing to New Vegas right at the outset.
- Equally however with good foreknowledge of enemy placement and where the important NPC's are in New Vegas you can have half of New Vegas on your side (the Brotherhood, The Kahns and The Boomers) before you even so much as think about finding out about where Benny went, the same can be said of Fallout 2, though the time limit in Fallout 1 limits how much you can do this
- Final Fantasy VI, once you hit the World of Ruin.
- Final Fantasy X-2. Technically most of the game is optional, but you'll need to do most of the side quests to be at a decent level.
- Mass Effect 1: There are plenty of sidequests to keep you busy, and you can do the main missions in any order you want. Do enough main missions, and more are unlocked.
- Mass Effect 2 belongs either here or further down the list. You are provided with an objective and a list of party members you can recruit to help you achieve it, some of them optional; there are also side quests which focus on those party members' Character Development and thus increase the likelihood of them having clear heads and steady hands once things start getting real. Of course, it also starts with a heavy-handed dose of Railroading in which you are forced to work for The Mafia just because they brought you Back from the Dead, so, there's that.
- Mass Effect 3 is even further down the list than 2, with the hub worlds being reduced to just the Citadel, and a much more compact mission structure (only 2-3 missions per world at most, as opposed to dozens in the previous games).
- Guild Wars has a main storyline for all three campaigns, but you can freely explore most areas of the world, with the chance to explore high end areas as a low-level character...if you can survive the onslaught of level 20 mobs in between (example: the run from Northen to Southern Shiverpeaks).
- Guild Wars 2: Both open world exploration and storyline are favored. Sidequests are replaced by Events, sort of what Side Quests would be like if their backstory was actually played out note and by trait gathering, which is Side Quests without exclamation marks note
- Xenoblade has a multitude of sidequests, vast open worlds and even Non-Combat EXP for completing the overarching Cartography Sidequest, getting achievements and Colony 6 reconstruction, both of which aren't essential to the plot (yet essential for achieving 100% Completion). The 60-hour campaign is just miniscule compared to the immense amount of sidequests, and some of these sidequests even give you smaller-scale stories on the worlds of Bionis and Mechonis.
- The Baldur's Gate series. Works very much like the Mass Effect example above.
- Romancing Saga and Romancing Saga 3.
- Crackdown and its sequel.
- The Precursors.
- Freelancer has a storyline which cannot be easily departed from (there are a chain of level caps, all the gear is level-limited, and you can't Open The Sandbox until you complete the earlier quests), but the storyline doesn't take much time, and after that it's a true Wide Open Sandbox. Of course, it's also not hard to completely max out your ride and have the entire map explored, at which point it becomes hard to set compelling goals.
- In Final Fantasy Tactics A2 literally only 20 of 301 missions (more if you count non-mission encounters with monsters or other clans and Brightmoon Tor) are main-story missions. Completing them all without any of the experience, unlocked classes, or loot (and thus gear) from non-story missions is nearly impossible but even then you can easily make it with only a very small fraction of missions completed if you have a small clan.
- Remarkably, A Spy in Isengard managed to reach a high level five, maybe even a low six, with a gamebook. You could go anywhere on the map, at your own pace and schedule, and return to locations you had previously visited if you wanted. There was an overarching quest, with a time limit, but if you didn't finish in time, that was merely a suboptimal ending, not a total defeat. Also, you could choose one of three different possible end points, although you did have to choose at the beginning. Some of the other books in the series had similar mechanics, although few would rank as high on the scale, but some, like Treason at Helm's Deep, which would probably constitute a level two, were much more linear. Since your typical gamebook was a level two or three, this was a pretty impressive feat.
- The first book in the series, Night of the Nazgūl, was also about a five technically, but since a lot of the location passages referred to the same encounter passages, it was like playing in a Wide Open Sandbox where you could go anywhere, but almost everywhere was identical to at least several other locations.
- S.T.A.L.K.E.R.. In all three games, until a few hours before the end of the game there is literally nothing stopping you from turning around and hiking all the way back to the starting area.
- The original King's Bounty was either a very high five or a low six. There is a time-limited quest that drives the game, and, in theory, the way to complete the quest is to go fight the enemy bosses, which you are encouraged to do in order, since they get tougher as you go. But you don't have to fight the bosses in order, or at all: a Pacifist Run is possible. There are some other limitations, mind you. You start out in the first continent and cannot travel to any of the others until you find the maps, but once you find the maps to open up each continent, you can sail back and forth at will. Also, you have access to a limited number of warrants at a time, so if you go after a later boss before catching at least some of the earlier bosses, you'll have to let him go, since you won't have the legal authority to arrest him. Within those limitations, however, you have a lot of freedom to explore and do what you feel like.
- Animal Crossing: While the game does give you the initial goal of paying off the mortgage on your house, that doesn't last long, and is only the very tip of the iceberg of what there is to do in this game. (You are also in no way forced to ever pay it off.)
- Dwarf Fortress, true to its nature, has no win condition, only a neverending series of lose conditions, all of which can be suspended indefinitely with relative ease. Adventure mode is even more wide open, but the lack of options that goes alongside the lack of limitations makes it more of a Level 2 in practice.
- The Elder Scrolls titles typically fall into this category. In Daggerfall, for example, it's very easy to forgo the main quest, especially since there is a time limit respond to a PC's letter. Beyond that, you are on your own to explore and seek out sidequests. Morrowind is much the same — there's a main quest, you have a pointer to it, and it's 100% optional. (The Expansion Packs for it shade down into Level 5, being far more structured and having less non-main-quest content.) As for Skyrim...well, Skyrim may be THE definition of open world.
- Skyrim does a lot of carrot dangling to try to get you to do the main story content. For example, while the game opens up immediately after Helgen, you have to keep playing the main quest for a little while if you want access to dragon shouts and some of the other quests and expansion material steer you back to the main quest. This is why about a third of those who play Skyrim do end up completing the main quest which is high for such an open game.
- Elona: Like Dwarf Fortress's Adventure Mode, except more pretty. You can do the main quest, but you're not forced into it, you can take as long as you like, and you can even turn it off.
- The Sims In Sims 3, 'story mode' alludes to often dichotomous plotlines for the initial housesholds when you start a new game, in true soap opera fashion, but there's little chance of any of these storylines proceeding without direct player intervention, and player-created families aren't included. There's no 'sandbox mode', but there are options to make the game even more open than the ostensible 'story mode' is. The earlier games are similar, although there are console versions that are somwhat more linear.
- World of Warcraft: While there are plenty of quests to give your character something to do, there is no overarching motivation or plot for your character beyond the eternal pursuit of loot.
- Cataclysm brings it down a notch - now there is a defined quest path through each specific zone and skipping parts of the zone is mostly impossible. But it still stays open in choosing the zone - this is only limited by character's level.
- Spore's Space Stage. Your homeworld gives you storyline missions, but you're free to ignore all but the introduction before going off to play with your tools in the celestial sandbox. You just have to watch out for your homeworld getting destroyed by aliens, as they never defend themselves.
- Turrets, my friend, turrets. Note also that this is a rare aversion of Sci-Fi Writers Have No Sense of Scale, at least in terms of how crazy huge a galaxy is (travel is still ludicrously fast for gameplay reasons.)
- Viva Pińata (at least Trouble in Paradise)
- Minecraft looks to be shaping up to be at this level. Though Notch states that he wants a "climax" of some sort, he also speaks of "emergent" plot and gameplay; it would probably be a surprise if you had to try to "win".
- That "climax" you pointed out being the Enderdragon, but most of the game's fun comes from the amount of things you can do.
- Most custom Adventure maps tend towards 1 or 2 if they have an actual plot. Wool collection maps are usually 3 or 4.
- There's actually Survival Maps made which basically follow the basic rules of Minecraft, but add some theme or twist, like being stranded on an island, or being stuck in the sky, or something along those lines. These maps tend to be anywhere from level 3 to 5.
- SimCity will let you build anything from a tiny mountain village to a huge metropolis, and from a dystopian wasteland to a paradise. As long as you avoid bankruptcy, the game goes on. Even if you burn the whole city to the ground.
- Most early simulation games are like that. You just get thrown into the game world with a hinted goal of "get rich". If there is a back story, it's All There in the Manual. This is probably the only genre that tends to go down the scale in sequels.
- EVE Online has player-run corporations, with all the various positions and routes for advancement that entails, and this economic system also allows for many forms of criminal activity and freelance work.
- LSD Dream Emulator has no plot besides the fact that it's supposedly a dream in one constant world (and it's pretty big) that changes the longer you play.
- Star Control II. It has a main quest. But even finding out what that is has to be done via exploration, let alone completing it. You're given the rather vague goal of "destroy the Ur-Quan", which is a tall order, considering that they have thousands of ships and you have... one. No, wait; two. You have to fly around a galaxy with hundreds of star systems and look for other civilizations who might be convinced to help in the fight against the Ur-Quan.
- Elite and the Fan Remake Oolite.
- Garry's Mod
- Egosoft's X-Universe series started as a level 5 (Beyond the Frontier gave you fairly clear indications on what to do next, and trading/building was finalized to doing the final quest), but quickly evolved into a type 6. In the later games, the player is given the choice of starting an entirely plotless game, where mission scripting is completely disabled, just so they can exploit the game's universe to their heart's content.
- The Saints Row series, because there are so many diversions from the main missions.
- The Russian FPS/RPG hybrids Xenus series (In America/Western Europe, the first game is known as Boiling Point: Road to Hell and the second White Gold: War in Paradise), which feature a rather open Main Quest with different ways to progress plus lots of sidequests for different factions in a large, open world.
- Yume Nikki technically has player objectives and an ending, but you'd never know it unless you read a walkthrough. Most of the gameplay simply involves aimlessly wandering around the protagonist's Dream World, and soaking in all the deliciously creepy atmosphere along the way.
- Terraria. You spawn with some basic tools and a Guide who tells you what you can build with any materials you have on hand and gives you tips on how to survive in the long term. Otherwise, it's up to you.
- The game's a borderline 5 or 6. While you are free to explore (mostly)wherever you want, the game has clear-cut boundaries on where you can, and how far you can go. Also, a lot of the game's focus tends to be on Boss-Hunting, especially after the addition of stronger versions of previous bosses in the 1.1 update. Many people got bored of the game after defeating all the bosses, simply because the game was set up as a sandbox game; so there was no plot or sidequests to follow afterwards.
- The 1.2 update adds new biomes (area types) and bosses to go with them. Oddly enough, this actually makes it a little more rather than less structured, since you can only reach certain bosses after defeating others (you can't get to Golem until you've defeated Plantera at least once, because you need the Temple Key Plantera drops to enter the area where Golem spawns).
- Second Life is pretty much the ultimate. Its not really even a game. You can design your own objects (even importing designs from sophisticated real world 3D design tools such as Blender and Maya) you can write scripts in an actual scripting language, you can even code your own Viewer for the world. The game's content is mostly generated by the players based on a real economy. But what really puts it at the extreme end of the spectrum is that you can build your own games and/or play games built by other "players." In fact, for the first 6 or 7 years, the only actual games to play were created by users.
- The only sandbox more extreme than this is Open Sim which is the open source code released by Second Life's creators. Its doesn't even feature the Linden's regulations.