Slicing tomatoes with a really sharp knife

And how this feeling relates to the user centered design approach


I used to hate slicing tomatoes.

The only knife we had was blunt. It always ended in squeezing the tomato until it was cut, or it started to squirt all over the kitchen floor. It was no fun at all. After receiving a really sharp knife, I completely changed my mind on cutting tomatoes.

Now there is barely anything more satisfying. The moment you set the blade on the skin of that plump and juicy fruit (yes, botanically that’s true), you get a thrill of anticipation. I think that comes from the way that the edge of the knife is gripping perfectly onto the skin. You know that you’ll be making a perfect cut. As you continue moving the knife forward, it is just an oddly satisfying and incredible effortless feeling how it slides through the tomato.

For everyone who is not able to follow me, I tried to capture this in the following film:


There are a lot of great products and interfaces out there. But only a few of them give you a similarly enjoyable experience to that of slicing tomatoes with a really sharp knife.

In the following text I tried to summarize a few relevant key points based on a user centered approach of designing and developing interfaces. I think these are essential for creating an experience comparable to slicing tomatoes with a really sharp knife.


Flawless Concept

Put the users first.

Lets say you have ideas for a new product, interface or service. One of the first things you should be asking yourself is who is going to use it. Try to get to know these people. What are they trying to accomplish? Are they aiming at a certain goal? Like getting an overview of the news, a detailed knowledge about a topic or just killing some time. Then try to find out what their abilities and disabilities are. What are they able to cope with? And furthermore where are they going to use it? What is the context of the product? Is it used in the morning commute on a train, in a classroom while working together, or in the evening while relaxing on the sofa?

Thinking of the users goals and needs can focus you to get just the right number of functions and possibilities. Designers, engineers and developers could solve a lot of problems by trying to understand the users situation better in the first place. The users will have a hard time choosing from too many possibilities. To less means they will not be able to reach their desired results.

Thinking of the users goals and needs can focus you to get just the right number of functions and possibilities. Designers, engineers and developers could solve a lot of problems by trying to understand the users situation better in the first place. The users will have a hard time choosing from too many possibilities. To less means they will not be able to reach their desired results.

Keep the big picture in mind.

Together with these principles of user-centered design, there is the need for the big picture. Where is your product coming from? Who is developing it? How will it be produced and distributed? Equally important is the question of what will happen after it gets abandoned, thrown away, or is just not working anymore. Is there a possibility to recycle, to replace or even to easily repair it?

Cut the crap.

After having thought of that, take a step back and check honestly if the product makes sense. Try to develop something that is useful, innovative and even makes a positive impact on the users social and cultural surroundings.


Evaluate and iterate the concept throughout the whole journey with profound research, appropriate prototyping and user tests. If you keep an eye on these points, you can create a flawless concept, which is also the base for creating a wonderful long term experiences.

Not keeping the users in mind can ruin the experience completely.

Crafted Details

Besides the conceptual thinking, the quality of the crafted details is important as well. They not only define the look and feel, but also the usability and can furthermore bring the joy to the everyday use.

Look and feel based on the users needs

Use typography, graphical elements and colors consistently to create an aesthetically pleasing interface. They should create an easily conceivable information and navigation architecture. Together with a layout that adapts to different conditions their goal is to support the users and to let them grasp the content and functionality in the most convenient way possible.

While this is substantial for the first encounter with the interface or the product, it is essential to look at all the details that happen while the users are interacting with it. It is crucial to use consistent interactions, which also depend on the user’s habits and circumstances. This new gesture recognition technology might be perfect for an enthusiastic student group, but just to hard to handle for the amateur. And how does the interface changes on interaction? Do the interface elements appear, change and disappear in a logical and meaningful way — not to interrupt — but to support the users in his tasks?

The users will probably not care that much about how your interface looks exactly. Yet will probably be frustrated if it is not designed consistently and if the same interactions are triggering different events.

Think of the details the users would not.

Interfaces and products, which are crafted at a really high level, will support the users in every detail. These delightful details are probably best if they are not promoted, but just happen, because then they can bring unsuspected joy to the users. This could include thinking of edge cases, bug handling, intelligent error messages and an impressive customer support. The users will be gladly surprised that somebody thought of it. Maybe this will come on only a few times in the use of the product or the interface.

In the same way as it can ruin the experience, it can also enhance it to captivating levels.

When a user can reach his desired goal efficiently through a supporting and delightful interface, it creates a feeling of slicing tomatoes with a really sharp knife.

Performance and Reliability

Performance is the bottom line.

No matter what your concept is or how carefully you crafted the little details: If it is not working, or if it is too slow to enjoy, then it destroys the whole experience. The load time of an application or a website can have a big negative impact on how the users are feeling about it. But it is not only the initial loading time. It continues with the reactiveness of the technology. How long does it take for the interface to react on the user’s interactions? If this is done correctly, the users will not be grateful for that. Instead they will see it as given base.

Reliability to ensure a pleasurable long term use

Together with the aspect of performance comes the one of reliability. Technology and materials which were used must be reliable and durable. Something that maybe excites in the beginning, will lose it’s reputation, if it is not reliable in the long term use.

Reliability of the technology is one part for assuring a pleasurable long term use.

I think, that if we try to keep these points in mind and put the users and their goals in the first place, we can create products, interfaces and services which will feel like slicing tomatoes with a really sharp knife.

Thanks for reading! #likeslicingtomatoes


Written and filmed by Nikolas Klein, 04|2015
Thanks to Erik, Matthias and Anita! Your proofreading helped me a lot.
Thanks to Christoph, Florian and Aaron for your feedback!
Starring Ester Harter and Dominic Fritsche!


A selection of books which were very helpful

Designing Interactions, Bill Moggridge
Especially the last chapter, which gives a great summary of interaction design as discipline and a great insight into the process!

Understanding Design, Kees Dorst
175 short essays on various topics around design in a very straightforward style!

Microinteractions, Dan Saffer
A must-read book for everyone who is in love with the smallest of details that matter a lot in the same way as I am.