Affordance

An affordance is a visual cue that says "use me this way" before you have read a word. Door handles are the classic: a bar you pull, a plate you push. Digitally, a raised button says "tap me," a blue underlined word says "follow me," a text field's blinking cursor says "type here." Good design makes the right action obvious through shape, color, and texture alone.

The subtle examples are everywhere once you look for them. The slight shadow under a button signals depth, which signals pressable. The horizontal lines on a scrollbar signal draggable. The way a slider thumb is circular but a toggle is pill-shaped signals two entirely different types of input. None of this is accidental.

Feedback

Every action needs a reaction, and it needs it immediately. When you tap "Send," the button should visually depress. Gmail shows "Message sent — Undo?" for three seconds. iPhone gives a gentle haptic on a long-press. Without feedback, users tap the button again. And again.

The loading spinner on pull-to-refresh. The progress bar on a file upload. The "typing..." bubble in iMessage. The subtle color shift when you hover a link. All of it is the same thing: the product saying "I heard you."

Visual Hierarchy

Your eye does not scan randomly. It goes to the largest, highest-contrast element first. Every good interface has one dominant element, one secondary tier, and one tertiary. A Stripe dashboard puts the revenue number at 36px and the label at 11px. Apple product pages have one word at 80px. NYT headlines are 48px, bylines are 12px. The proportions are doing the work.

The subtle version: the way a pricing page makes the price huge and "/month" tiny. How error messages are red while success messages are green. How recipe cards bold the ingredient name but not the quantity. Color and size as hierarchy, not decoration.

Fitts's Law

The time it takes to hit a target is a function of its size and distance. Bigger targets that are closer get tapped faster. This is why "Continue" spans the full width of a phone screen, while "maybe later" is a small ghost link buried far below. macOS's dock magnifies icons as your cursor approaches, actively shrinking the law's penalty in real time.

Phone keyboards have larger keys than desktop keyboards. The iOS back button is always in the top-left thumb zone. Screen corners are infinite targets because the cursor physically cannot go past them. None of this is aesthetic. All of it is physics applied to interface design.

Progressive Disclosure

Show the simple path first. Reveal complexity only when the user is ready for it. TurboTax shows one question at a time. iPhone Settings is a nested hierarchy where you only go deeper if you need to. LinkedIn truncates long posts with "see more." The principle keeps beginners from drowning while still preserving depth for the people who want it.

Camera apps show basic controls by default and hide pro settings behind a swipe. Figma has Basic and Advanced properties panels. Gmail hides CC/BCC until you tap to expand. The complexity is always there. The skill is deciding when to surface it.

Recognition Over Recall

It is easier to recognize an answer than to retrieve one from memory. Google autocomplete is the clearest example: type two letters, see the full query. Slack puts slash commands in a menu because nobody memorizes 40 shortcuts cold. Dropdowns let you pick a country instead of type one. The design does the remembering so you do not have to.

Recent files shown before you open a picker. Browser history suggestions in the URL bar. Emoji keyboards grouped by category so you browse instead of search. Spotify's "Based on your recent listening" so the decision is already half-made. The pattern is consistent: surface the answer, do not make people retrieve it.

Consistency

Users spend most of their time on other products. They arrive with existing mental models built from years of using everything else. If your back arrow is in an unusual place, your save icon is unfamiliar, or your navigation is inverted, cognitive friction spikes. Familiarity is a feature, not a concession.

The hamburger menu sits top-left. The search icon is always a magnifying glass. The X always closes things. Blue means links almost everywhere. These are not conventions because someone decided they were correct. They are conventions because enough products used them that users internalized them, and now any deviation costs something.

Where All of This Actually Lives

These principles feel invisible in great products because they are working exactly as intended. They reduce friction so quietly that you only notice them when they are gone: the door you push that has a pull handle, the form that gives you no error message after you submit, the button that does not respond when you tap it.

The goal is never to be clever about design. The goal is to get out of the way. When these seven principles are working together, you get an experience where the user is thinking about their task, not the interface. That invisibility is the whole point.