Lock Mechanisms in Game Design
by Jonathon Schilpp


This article focuses on a common feature of game design, which I will call a "Lock" mechanism. Although Locks may be found in many types of computer games, they are of critical importance to Adventure and Role Playing Games (RPGs.)

In order to craft a superior RPG or Adventure game, the gameís designer must do quite a lot of work. An entire world must be constructed. If the player is allowed to steer his character through this world unhindered, large sections of the game may be missed entirely.

To avoid this problem, the designer implements a Lock. This guarantees that the player will not venture further into the game world until he has more fully explored the areas he has already discovered.

How Does a Lock Work?

Here is a simple example of the Lock mechanism. Suppose that a playerís character has just entered a castle. There is a dungeon beneath the castle, which the player is eager to explore. But as a game designer, you have spent countless hours creating this castle. You have spent many late nights fashioning each NPC, and each has his own, special personality. You certainly donít want the player to bypass all that hard work. How will the player ever appreciate your genius for game design?

In this case, you might use a Lock, something which will prevent the player from venturing into the dungeon. This may be be simple and boring, like a locked door. Or it may be something a bit more interesting, like a disgruntled castle guard who, in a fit of desperation and delerium, has barricaded himself in the dungeonís entrance. Whatever the details, the dungeon is blocked.

In order to progress further into the game, the player must find some way of getting past the Lock. The solution which enables the player to bypass the Lock is called a Key. This may be as simple as finding a key which unlocks the door, or as complicated as solving an intricate puzzle. Whatever the details, the player cannot reach the dungeon until he has explored at least some part of the castle.

Some Common Types of Locks

All Locks have the same basic purpose. They are intended to temporarily block the player from further exploration of the game world. Locks come in many forms. A Lock may be a locked door, a ferocious beast blocking the path, a bad snowstorm which prevents travel, or anything else that a designer can imagine which will do the job.

Some Locks are so common that they deserve special mention. One common type of Lock which is a standard feature of Adventure games and RPGs is the Puzzle. There is a big difference between a puzzle which is used as an element of gameplay (such as in Tetris,) and a Puzzle which is used as part of a Lock mechanism.

Used as a Lock, the point of a Puzzle is to limit access to parts of the game world. Typically, the player encounters some obstacle, such as a path blocked by flooding, a deep chasm which cuts through a path, or something similar. In order to progress further into the game, the player must devise a solution to the Puzzle. Perhaps he must build a boat, or find something to lay across the chasm.

Switch Locks are common in Adventure games. In this case the player may encounter something like an electronic security fence. Or perhaps it is an elevated platform which is too high for the player to reach. Somewhere else, in an area the player has not yet explored, is a Switch will allow him to venture further into the game. The Switch may cut the electricity to the security fence, or it may lower the elevated platform. Of course, the Switch can be a button, computer terminal, or something else. The important point is that the obstacle is overcome by finding a release mechanism in an area some distance from the obstacle.

In RPGs, a player may encounter a Quest. This is also a Lock. In this case the player may not advance the storyline until he has performed some task. He may need to speak with a certain character, retrieve some medicine, slay a monster, rescue someone, find the Sacred Sword of the Goblin Slayers of Old, or whatever the game designer can imagine at the time.

How Are Locks Misused?

Many designers fail to use Locks properly. When Locks are poorly implemented they can have a very negative impact on the overall gaming experience. Sometimes Locks are overused in a game. Or they may be boringly similar to one another. Or they may kill the flow of the game by making the player stop and search for a Key just when suspense was building in the game. As an example of poor use of Locks, I would like to examine how they were mishandled in a game which was released a few years ago. (I will not name this game, for obvious reasons.)

This was an Adventure game, and it could have been great. The game concept was fine: an Adventure game in which players would explore a series of dungeon levels, seeking treasure and battling monsters along the way. There were a number of problems with the final product, but one of the things which doomed it right away was its horrid misuse of Locks.

All of the Locks in this game were either Switches or Doors. All of the Switches looked and functioned identically. All of the Doors looked and functioned identically. The Locks were overused, and were not implemented creatively. Even had the rest of the game been great, this misuse of Keys doomed the game to failure.

Here is the pattern which the gameplay followed, almost exactly. On any given level, the player was required to do the following: 1) Find the Silver Key, in order to 2) Unlock the Silver Door, allowing him to 3) Find the Red Key, which would enable him to 4) Unlock the Red Door, beyond which he must 5) Find the Gold Key, so that he could 6) Unlock the Gold Door and 7) Acquire yet another worthless magic sword and 8) Proceed to the next level, where the tedious proceedure would be repeated.

This unimaginative routine was already stale before the end of the first dungeon level, and grew more tiresome with every passing moment. What should have been an adventure was instead a frustrating experience. It goes without saying that the game was a dismal commercial failure.

Proper Use of Locks

The sort of design nightmare featured in the last section can easily be avoided. A game designer who cares enough to invest some time and imagination can easily master the art of using Locks effectively. In some games, like that awful Adventure, misuse of Locks can detract from the gameplay. But there are a few simple rules which will guarantee that Locks have a positive impact, leading to a better game experience.

The first rule is that the Locks must be varied. If a player encounters one or two locked doors in the course of a 50 hour game, there is no problem. But if, after the first fifteen minutes of play, the player has already encountered four of them, there is an obvious problem. On the other hand, if a player has come across one surly castle guard, a trap door in the ceiling, a backstabbing Goblin and a secret door he cannot figure out how to open, the game is much more interesting. So rule one is: Locks Should Be Varied. The designer should use his imagination as much as possible. This can be a real challenge, but the effort will be rewarded with a much better game.

The second rule deals with efficiency. If the player is required to find a Key to every Lock in the game, there will be too much time spent on finding Keys, and not enough time enjoying the game. Therefore it can be useful to use one Key which opens multiple Locks. An example of this might be when the player has the favor of the King. It is amazing how many doors this Key will open! So the second rule is: Keys Should Be Efficient. With proper planning, a game world may be devised so that a single Key may open several sections of the game world without any detrimental effect.

Sometimes a player may be required to go to considerable trouble to acquire a Key. When this is the case, being allowed to progress further into the game may not be enough of a reward. This is particularly true when the much-sought Key becomes just a worthless entry on an inventory list. "Gold Key," a player might sigh. "Thatís that darn key I had to spend an hour trying to find. Itís useless now. I suppose I may as well just discard it."

But Keys do not have to become useless once they have served their purpose. A useful magic item, weapon, spell or tool can also be used as a Key. This leads to the third rule: Keys should be useful. A player is bound to have far less appreciation of an inventory item named "Key" than for one named "Fireball."

One aspect of Lock design which is often overlooked by game designers is realism. The game world is bound to have its own, unique reality. And yet, even in a game, things can be unreasonably unrealistic. Consider the way some designers use Switches. In some game worlds, Switches are everywhere: on the walls, on the floors, in the garden, on the roof, on the familyís pets..., (Well, O.K., the pets are usually safe. But nothing else seems to be!)

But is this logical? What kind of moron would design his house so that the bedroom door could only be opened by throwing switches in the kitchen and diningroom? The idea is insane! Yet many game designers expect their players to accept similar inconsistencies.

Using Locks illogically also endangers the "suspension of disbelief," one of the most important elements of game design. For these reasons, the fourth rule is: Locks and Keys Should Be Realistic.

In some game genres, most notably Horror, the mood of the game is of critical importance. Creating and maintaining a necessary mood are difficult tasks. So it is unfortunate that designers sometimes ruin the mood of their games by using Locks which are not in keeping with the mood of the game. Once lost, mood is something which is difficult to regain. So the fifth rule, which is very important in some games, is: Locks and Keys Should Be Compatible With the Mood of the Game.

And finally, the single most common misuse of Locks may be overuse. Finding a Key may not be a hassle once in a while, but too much searching for Keys can be tiresome. In some games, a player is required to search for Keys almost constantly. In these games, searching for Keys is usually used as a substitute for gameplay. In other games, the player must constantly backtrack to fetch Key items. In my opinion, these are both signs of poor game design.

I would like to point out that finding a Key should almost never entail backtracking. The Lock mechanism should be used as a tool to make the player explore areas not yet visited. Backtracking, on the other hand, forces the player to return through an already explored area. This is why fetching Keys is such a boring process in many games.

So the last rule is: Do Not Overuse Locks. There are few things which can ruin an otherwise great game so quickly as overused Locks.

A Shining Example

In an earlier section of this article, I gave an example of a game which misused Locks. I would like to balance things by providing an example of how Locks were used effectively in another game. This game I will name, if only out of respect to the hard work and skill of the gameís designers.

Castlevania: Symphony of the Night is a game which was published several years ago by Konami. In this game, the player controls the son of Dracula, and explores Draculaís Castle. Along the way, the player learns to use his characterís vampiric abilities. What may not be readily obvious, is that these abilities were the Keys to many of the gameís Locks.

The first rule says that Locks and Keys should be varied. In this game, the Locks were things like ledges, holes in the ceiling, cliffs, and cracks in the walls. The Keys were varied as well. These included the ability to jump higher than normal, the ability to transform into a wolf, the ability to fly, etc. So the Locks and Keys were varied nicely.

The second rule says that Keys should be efficient, and that was certainly the case in this game. When the player achieved the ability to jump higher than normal, he was able to gain access to many ledges throughout the Castle. And when the player obtained the ability to fly, many more areas became available. So the Keys were very efficient.

Of course, all of these vampiric abilities were very useful to the player, which is in accordance with the third rule. (And letís face it, transforming into a bat is just cool!)

The fourth rule says that Locks and Keys should be realistic. The locks were realistic enough: ledges, doors, crumbling walls. Of course, if my neighbor were to transform into a wolf this afternoon, I would find it unbelieveable. But in a game about vampires, this is realistic enough. And the Keys functioned realistically. It is natural to believe that a bat can fly, and therefore reach a ledge which is out of reach to a human.

And of course these Keys were in keeping with the mood of the game, as the fifth rule suggests. But more than this, the Keys in this game actually added a lot to the game experience.

The sixth rule says that Locks and Keys should not be overused. Thanks to careful, creative consideration, the designers were able to implement a great many Locks without overusing them. Because the Keys were so efficient (rule two,) and useful (rule three,) the Keys never got in the way of gameplay.

Warning Signs

Proper use of Locks is no accident. It is the direct result of careful, creative planning. And misuse of Locks is no accident either. It is the direct result of poor planning and inferior game design. At the risk of sounding pompous (which I may have been guilty of since section five,) I would like to offer some suggestions to game designers who may not have used Locks as effectively as possible in the past. Of course, every project is different, and these guidelines need to be modified accordingly.

The most common misuse of Locks are lack of variety and overuse. Lack of variety is easily addressed. If all of a gameís Locks and Keys look and function identically, the problem will be immediately obvious. A little creativity will solve this problem easily. But overuse is more difficult to judge.

I would suggest, as a general guideline, that no game should require a character to search for a key to a locked door more than twice. Even in a full-length RPG this gets boring.

Switch mechanisms are O.K., but actual, physical switches get boring very quickly. If there are more than two in any game, the designer may need to look at them carefully, and determine whether a Switch may be implemented differently.

Passwords are often used as Keys. But this should be a unique situation. I would suggest that any game which is not set in a military compound, prison, or similar setting should have no more than one password Key.

When an item is used as a Key, it is best to make it a useful item. I would suggest that no more than three Keys should become useless after opening Locks.

And lastly, I believe that with careful design backtracking can usually be avoided entirely. If backtracking is used, I think it should be limited to once or twice at most.

As I mentioned, these are only meant as guidelines, and must be modified or ignored whenever necessary.

A Final Word

The Lock mechanism can be a powerful and vital tool for game design. But like any tool, it must be used intelligently and creatively to be truly effective. In the end, I may not have said anything in this article which is not readily apparent to anyone who examines Lock mechanisms. Nevertheless, they are often misused. I hope this article will open discussion of a topic which has been largely ignored - to the gamersí detriment.

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Date this article was posted to GameDev.net: 6/16/2001
(Note that this date does not necessarily correspond to the date the article was written)

See Also:
Game Mechanics

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