Roku SDK Documentation : Key Design Principles

A UI is invisible when users remain focused on their goal of navigating and watching the content instead of figuring out how to use or operate the UI. An invisible UI never draws any unnecessary attention to itself; it's effortless to use because everything about it is evident, requiring very little learning or energy. In its cognitive economy, users are never confused. Constantly ask these key questions about your UI as you're designing and reviewing it.

  • Is your UI getting in the way? TV viewers want to relax, have a beer in one hand, and a remote in the other. Then, with as few actions and decisions as possible, watch something great. No one wants to use a UI; they just want to watch something entertaining. So, remember that your UI needs to be a delightful and useful tool.
  • Is it easy to use? The most common design mistake is making the UI too complicated. People not only need to operate the individual onscreen UI elements (micro-usability) smoothly but be able to accomplish their goals (macro-usability) easily. People need to know where they're at and where to go next, which means the navigation must be simple and obvious. Reducing complexity is more important than reducing the number of steps. Simplicity trumps speed.
  • Is it snappy? The system must respond immediately to every user action with clear and distinct feedback. The UI needs to be highly responsive; otherwise, interactions will be frustrating. Transitions, animations, and load times must all be optimized for performance.
  • Is it easy to learn? No one expects or wants training on how to use their TV! Instructions on how to use the UI are usually a sign of a weak design. Patterns and consistency mean actions and outcomes are predictable, which enables users to carry what they learn from one screen to other screens. Can you describe how to use your UI with the fewest number of "always true, simple rules"? The more exceptions there are to the general behavior of your system, the more complicated it is to learn and use.
  • Does it look simple? The look of a UI also contributes significantly to its delight and ease of use! Ensure people can easily tell where the focus highlight is and where it can go. Create visual hierarchy so what's important has prominence and what's secondary is pushed back, demanding less attention. Keep screen information density low; blank space is essential, giving screen elements room to breathe and reducing a user's anxiety.
  • Is there too much? More is not always better; more features, more choices, more information can lead to more work, noise, and complexity. Start with less to keep it simple and approachable; focus on the few things that have a significant impact and are relevant to users and their tasks. Eliminate all others. Later look for signs or evidence of what more is needed.
  • Does it flow? Not only do you need to ensure that the sequence of steps a user must take from screen to screen flows in a logical and predictable order, but there should also be a consistent and natural flow on the screen itself. Avoid screen designs in which users must jump their gaze and focus all over in an unorganized or poorly choreographed order. A single pass top-down, left-right flow is the best when it comes to the final actions towards the right and/or bottom of the screen. The size, color, contrast, and placement of each element work together, creating a clear path to understanding your interface.
  • Is it seamless? Jumping or cutting from one state to another forces people to re-evaluate the new state and re-orient themselves. So, use simple, clean, and minimal animations to help users see and follow the system's transition from one state to another. However, never make people and their interactions with the system wait on animations (UI animations should not act as a governor to throttle the pace of the interaction). As your UI transitions from screen to screen, ensure a relevant element from the first screen carries over to the next screen for continuity of the context.
  • Is it focused? To ensure better clarity and simplicity for any given screen, design each screen to have one specific purpose and make sure everything on that screen serves that single purpose. Don't overload screens and try to do too much at once. One screen, one purpose.
  • Is it forgiving? No matter how clear your design is, people will make mistakes. You should handle user errors with as much attention to simplicity as the rest of the UI. Ensure users can easily back up, resume, and avoid dead-ends; always provide a way forward. Use error messages as a teachable moment and avoid technical language, placing blame, or making people feel stupid. Users must have a sense of comfort and trust at every step.
  • Is it entertaining and engaging? Remember, you're creating an entertainment experience, so the UI itself should also be engaging and a joy to use. Be more visual and celebrate artwork and images, like movie posters, and make them big. Keep the UI experience human, approachable, light-hearted and comfortable throughout the screen. Pay attention to the tone and the wording of the text. People are fearless when playing games; they don't worry about breaking it. We too are creating an entertainment experience, and our system needs to be as approachable and forgiving as possible.
  • Is it legible? People sit an average distance of 10 feet (3 meters) from their TV screen. While the TV screen may seem like a large display with plenty of UI screen real estate, from 10 feet away, the relative size of the TV screen can be smaller than a phone held 1 foot away from your face. Therefore, ensure everything is easy to read with high contrast and large text. The larger text has the added benefit of forcing you to be concise and reduce the total amount of information shown (information density) to just what's important.
  • Is it overscan safe? TVs were made of cathode ray tubes (CRT) in anticipation of overscan that produced inconsistent images across TV sets, especially along the screen edges. To compensate, CRT TVs used overscan, which slightly enlarged the image itself so those bad screen edges would be outside the viewing area. You should avoid showing any critical information too close to the edge of the TV screen. Since overscan still exists even on HDTVs, Roku recommends you set at least a 5% margin within which to keep all of your UI to ensure its visibility. For a standard HDTV with 1920x1080 pixel resolution, this means having a 90 pixel left/right side margin and a 60 pixel top/bottom margin.