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Portal 2 Level Design: Creating Puzzles to Challenge Your Players

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This post is part of a series called Portal 2 Level Design.
Portal 2 Level Design: From Initial Idea to Finished Level

Portal was one of the most distinctive puzzle games of the past few years, and its sequel Portal 2 showed us that lightning can strike twice. A little less than a year ago, Valve made waves once again by introducing a simple yet powerful level editing tool in Portal 2 itself. In this article I'm going to discuss how to design great puzzles that will challenge your players.

Thinking With Portals

Designing levels for Portal 2 is very different to designing levels for other games. To design strong levels for Portal you need to have a strong understanding of the gameplay as a whole and of how the different gameplay elements interact with each other. Before sitting down with the level editor you should do some prep-work to get in the right frame of mind to be thinking about Portal levels.

Take some time to play community-made maps such as Rendezvous, Only as Difficult as You make it, and Suspended. Not all of the community maps are perfect and some of them are herculean tasks to complete, but it's worth it. The simple fact is more maps have been made by the community then Valve ever could have made on their own and many of them are quite incredible. Also, have a notebook at hand so you can take notes about interesting interactions between puzzle elements and about how different puzzles work. I find it's best to write down the solution to some of the more unique or challenging puzzles in a step-by-step manner because it really helps me evaluate what made that puzzle so intriguing or difficult.

The Steam Community hub for Portal 2.The Steam Community hub for Portal 2.The Steam Community hub for Portal 2.
The Steam Community hub for Portal 2.

Finally, spend some time learning everything you can about the different puzzle elements in Portal 2. I find it often helps to have a list of the different puzzle elements and the basic things they can and cannot do next to me when I'm working because it keeps me from forgetting any individual element and allows me to more easily consider the interactions between the elements when they are all right next to me.

Generating Ideas

I'm not going to lie: coming up with ideas for Portal levels can be very challenging. Unlike level design in most other games, where your idea can come from the type of environment you want and the goals you want your player to achieve, Portal levels are all about the task at hand - they are all about the puzzles themselves.

Because of this, I find that one of the best ways to come up with a Portal level is to start with a puzzle mechanic you want to focus on. For example, you may be a big fan of laser redirection puzzles or you might love aerial faith plates. No matter what you prefer, determining the type of puzzle you want is always a good first step because it helps you more easily define what type of puzzle you are trying to make. For example, if you plan on using lasers in your puzzle you probably won't be making a small test chamber, and if you plan on using the white gel then you will probably have less portalable walls than the player needs to solve the puzzle, to necessitate the use of the gel.

Tip: This is where it comes in handy to have a list of all the tools and puzzle mechanics so you don't forget any or neglect any possible ideas.
The tool box from the in-game editor, with all the available puzzle elements.The tool box from the in-game editor, with all the available puzzle elements.The tool box from the in-game editor, with all the available puzzle elements.
The tool box from the in-game editor, with all the available puzzle elements.

Another way to generate ideas for a puzzle is to think of the overall concepts you want the puzzle to involve or the actions you want the player performing. Maybe you want a puzzle with a large pool of water in the middle where the player is constantly going from one side to the other, or a chamber which is divided into quarters by two criss-crossing fizzlers. This is very similar to the previous method except you are now thinking in terms of the actions the player will be engaging in while solving the puzzle rather than the specific tools they will be using to perform those actions.

Overall, it's best to start with the broad strokes of the puzzle such as the main goal or actions by the player so that you have a guiding vision and the move on to the more specific details as you develop it. It will be much easier to figure out where to place the cube dispenser once you know what the cube will be used for than it will to try and figure out what to use a cube for when that's the only thing you have in your level.

Building the Level

Once I have the overall idea down I start drawing things out on paper or in a sketching program. While my drawings won't be perfect I still like to get a basic layout down so I have something to work from when I go in the editor and so I can start seeing how the puzzle elements may interact and can find the most basic problems quickly. I also use this time as another brainstorming period and try to think of multiple potential layouts that could all work for the same idea.

These are notes I put together while working on a level idea I'll be making in a future article.These are notes I put together while working on a level idea I'll be making in a future article.These are notes I put together while working on a level idea I'll be making in a future article.
These are notes I put together while working on a level idea I'll be making in a future article.

With basic concepts complete, it's time to get in the editor and see how the ideas will actually work out. The great thing about the Portal level editor is that it allows you to use iterative design techniques very effectively so that if you don't like how something is working, you can quickly make the necessary changes and test the new version to see if it helped. This part of the process is the most ambiguous since no two people want the same things from their levels. While I can't tell you exactly how to build your level, there are some things that you should keep in mind that may help.

Challenging, Rather Than Frustrating

The first thing is the idea that your level should be easy to comprehend, but challenging to complete. A puzzle of any kind, not just a Portal level, is only fun when the player clearly understands their goal but is not necessarily sure how the goal is accomplished. If they don't know the goal, they cannot proceed and will only get frustrated, and if they already know how to complete it then there will be no challenge and it won't be interesting.

To make a good puzzle you must balance the player's understanding with the puzzle's challenge so they understand what needs to be done, but not the actions that need to be taken to make it happen. To avoid these issues, make the goal visible from the start of the level. When the player walks into the test chamber they should already have some idea of what they need to do. Even if they don't yet know how to finish the level, they should know what they need to do at that moment so they are not left pondering their first action for an extended period of time.

I can see my goal but I am unsure how to reach it.I can see my goal but I am unsure how to reach it.I can see my goal but I am unsure how to reach it.
I can see my goal but I am not sure how to reach it.

Inherently Rewarding

Next, you want the player to have a sense of accomplishment when they complete your puzzle. From the player's perspective, the best part of Portal is the moment when they finally figure out how to solve the puzzle and get their solution to work. To give the player this feeling you have to make sure there is room to fail as well as to succeed. This boils down to how you use black walls, or non-portalable walls, vs. white walls, or portalable walls. If you have too many black walls and only have white walls in specific spots your puzzle will not be fun because the player will have no real choice in how they solve the puzzle or how they arrive at the solution. On the other hand, if you don't use any black walls it may open your level up for solutions you didn't intend which are much simpler or less interesting than what you had in mind when you made the puzzle.

Overall this issue is going to become most obvious through playtesting - so, as usual, do lots of that. It also just helps to be aware this can be an issue and to consider it while laying out your puzzle.

Author's Note: It was pointed out by a commenter on the YouTube version of this video that the white walls on the left and right should actually end at the point where the platform the player needs to get on begins. If they don't then the player is able to place a portal at the edge of the black wall and step out of the portal onto the ledge without performing a fling mechanic.

Editor's Note: I guess this underscores David's later point about playtesting being crucial!

Re-Using Puzzle Elements

The final thing I want to mention here is using puzzle elements in multiple ways. A lot of the most interesting puzzles I have played require you to use the same puzzle elements multiple times throughout the level and don't always make it obvious how many different ways, or what new ways those elements need to be used later on.

Now let's be clear, I'm not saying that if you are making a puzzle with lasers you should have multiple different laser emitters around your level and have your player use lasers a bunch of times, I'm saying you should try and design puzzles with limited numbers of each element and then force the player to go back to elements they already used earlier in the puzzle to use them again in a new scenario. In the video below I play through a level which does this in a simple yet effective manner and you can see exactly what I'm talking about.


Designing levels in Portal is a unique challenge. As I said earlier, it is different from many other games in that the attention is entirely on the gameplay and often if you try to add a lot of flourishes by bringing your level into Hammer (the standard map editing tool for Valve games), to use more unique textures and props, it may just distract or confuse the player. If you are building your level in the built-in level editor then the only things you have access to are the things that will affect the gameplay, so really nailing down those gameplay elements and making sure everything is just right is incredibly important. This is both a good thing and a bad thing depending on your perspective but really it's just a sign you should do a lot of playtesting.

When playtesting, do your best to find as many solutions to the test chamber as you can. Hopefully your test chamber can be solved the way you intended but you also don't want to limit your chamber so that that is the only way it can be solved. Specifically you need to find the ways the player can manipulate the rules of Portal so that they can solve the puzzle and skip what you intended to be the puzzle's solution. You may have issues like this because you didn't eliminate enough of the white walls like I said earlier, or because you didn't realize the player would be able to get a second cube onto the other side of a fizzler - whatever the problem is, you need to find it.

I find during this stage it really helps to bring in other players. Everyone thinks differently and you will never think of all the solutions ten of your friends will in the same amount of time. In the end you really just need to playtest as much as you can until the only solutions available are ones you are happy with. Also remember, just because a solution is not the one you intended, it doesn't mean that solution is bad; don't cut it just because it's not "correct".

Closing Remarks

A lot of the Portal design concepts may be hard to grasp at first because puzzle design is a somewhat complex subject, but as always practice makes perfect. I hope this article helped you get a sense of how to design levels for Portal and what you need to consider, but if some of the concepts still seem strange to you, make sure to come back soon for my step-by-step guide here on Gamedevtuts+ where I'll design a Portal level from the ground up and explain the reasoning behind my decisions.

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