Critical Path Newsletter

The Principles of Great UI Design

If there were simple rules you could follow and create a great interface every time, then there would be no bad interfaces. Users would find the features they’re looking for without hunting for them. Everything would always be intuitive. The people who write online help would have to hit the unemployment lines.

Fortunately for technical writers, but unfortunately for the rest of us, it’s not that easy. Solid rules you can follow to come up with great output every time just don’t exist.

Don’t lose hope. Good interfaces might not follow a set of mysterious rules that tell you the answers to every problem, but there are principles that help you make the right decisions when it comes to design.

Every good interface takes these things into account:

• Design tradeoffs – When you make any design decision, you sacrifice one aspect for another
• Design interactions – Features don’t exist in isolation, they are part of the whole package
• Design assumptions – Some design is based on our best guesses rather than user research

Design tradeoffs

Designers know it’s great to put all the features at the user’s fingertips. Designers also know that it’s great to keep the design uncluttered and simple.

But what if the application has a ton of features? What if making all the features available leaves you with a work area the size of a postage stamp or makes the screen more cluttered than the cubicle of a developer with a Lego collection? What do you do then?

Every design decision is a trade-off against another aspect of design. When you get to a critical mass of features, you can’t have both simple design and all the features readily accessible.

There’s no magic bullet to tell you when to simplify the design and when to load up the features on a page. You have to decide for yourself where the best balance lies for each application.

Knowing your target users helps out here. For example, if you’re designing an .mp3 player for senior citizens, you would make a different choice than if you were designing one for the teenage marketplace. One might appreciate simplicity more and the other might like more options (You can figure out which is which).

Design interactions

When a design decision in one aspect of an interface ends up affecting a user’s interpretation or experience with another aspect of the user interface, that’s a design interaction.

Let’s look at an example:
In one version of Microsoft Outlook, a user could access the “Find All” feature by looking under the Actions menu. But, under the Tools menu, the user could also find the “Find” feature. In this case, the “Find” and “Find All” features potentially interact in the user’s brain, and therefore in the user’s actions, which affects usability.

Having a similar feature repeated with different names in different locations risks some potential disadvantages. For example, a user might look for the “Find” feature associated with the Tools menu under the Actions menu, then get frustrated when finding the “Find All” feature doesn’t work as expected.

Before being too critical of this particular example, we have to remember point #1—design tradeoffs. Possibly the designers faced some serious design tradeoffs and came up with this as the best solution to the problem. Hard to say.

But we can guess that the designers made a tradeoff here. Maybe the convenience of the functionality in two likely places vs. the confusion of it being in on two menus.
The key is to always remember that you’re making tradeoffs and to make them in the most reasonable and logical way you know how.

Design assumptions

In an ideal world, we could create every design the scientific way, based on real data—by testing it with live users, tweaking the design, then testing it again until it was utterly intuitive. But because of time and budget constraints, that isn’t going to happen anytime soon.

So, we make assumptions—our best guesses.

We make assumptions about what is important to users, how they’ll react, how they interact with the software, their work environment, and so on. As smart as we are, we don’t always get it right.

User research and techniques like user personas and user interviews can take some of the guesswork out of design decisions that involve users. For example, what if you must decide between adding an underlining feature to your word processor or a green highlighter? It might be helpful to know what percentage of your user base might be red/green colorblind. Makes the decision a lot easier.

Design questions don’t always have simple answers. In fact, they usually don’t.

Identifying each side of the issue can help you make smart choices when it comes to design interactions. Researching your users can help you decide what tradeoffs to make, plus help you make intelligent assumptions when it comes to design.
No solution is perfect, but with these issues in mind, you can increase your odds of a great design.