Design of Everyday Things Framework
Foundational design principles for creating products that are intuitive, discoverable, and understandable. The "bible of UX" — applicable to physical products, software, and any human-designed system.
Core Principle
Good design is actually a lot harder to notice than poor design, in part because good designs fit our needs so well that the design is invisible. When something works well, we take it for granted. When it fails, we blame ourselves — but the fault is almost always in the design.
The foundation: Design must bridge the gap between what people want to do and what the product allows them to do. The best designs are discoverable (you can figure out what to do) and understandable (you can figure out what happened).
Scoring
Goal: 10/10. When reviewing or creating designs, rate 0-10 based on discoverability, understandability, and error prevention. A 10/10 means users can figure out what to do without instructions, understand what happened, and recover from errors easily. Always provide current score and improvements to reach 10/10.
The Two Gulfs
Every interaction with a product requires bridging two gulfs:
USER PRODUCT
│ │
├──── Gulf of Execution ────────────────→│
│ "How do I do what I want?" │
│ │
│←──── Gulf of Evaluation ──────────────┤
│ "What happened? Did it work?" │
Gulf of Execution
The gap between what users want to do and what the product lets them do.
Questions users ask:
- What can I do here?
- How do I do it?
- Which control do I use?
- How do I operate this control?
Bridging strategies:
- Clear signifiers showing what's possible
- Natural mappings between controls and outcomes
- Constraints preventing wrong actions
- Familiar conceptual models
Gulf of Evaluation
The gap between what the product did and what users understand happened.
Questions users ask:
- What happened?
- Did it work?
- Is this what I wanted?
- What state is the system in now?
Bridging strategies:
- Immediate, visible feedback
- Clear system state indicators
- Meaningful error messages
- Progress indicators
Design goal: Make both gulfs as narrow as possible. The ideal design requires zero bridging — action and understanding are immediate.
See: references/two-gulfs.md for gulf analysis exercises.
Seven Fundamental Design Principles
1. Discoverability
Definition: Can users figure out what actions are possible and how to perform them?
Five components of discoverability:
- Affordances
- Signifiers
- Constraints
- Mappings
- Feedback
(Each detailed below)
Test: Put a new user in front of your product. Can they figure out what to do within 10 seconds? If not, discoverability is broken.
Anti-pattern: "The user manual explains it." If users need a manual, the design failed.
2. Affordances
Definition: The relationship between the properties of an object and the capabilities of the agent (user) that determine how the object could be used.
Key insight: Affordances exist whether or not they are perceived. A door affords pushing whether or not you know to push it. What matters is perceived affordance.
Types:
| Type | Definition | Example |
|---|---|---|
| Real affordance | Physical capability exists | A button affords pressing |
| Perceived affordance | User believes capability exists | A raised area looks clickable |
| Hidden affordance | Capability exists but isn't obvious | Right-click context menu |
| False affordance | Appears to afford action but doesn't | A decorative element that looks clickable |
| Anti-affordance | Prevents action | A barrier that blocks movement |
Digital applications:
| Element | Affordance | How to Signal |
|---|---|---|
| Button | Affords clicking/tapping | Raised, colored, shadow, hover state |
| Text field | Affords text input | Border, placeholder text, label |
| Link | Affords navigation | Color, underline, cursor change |
| Slider | Affords dragging | Handle, track, visual range |
| Scroll area | Affords scrolling | Scroll bar, fade at edge, partial content |
Common failures:
- Flat design removes perceived affordances (is it a button or a label?)
- Touch targets that are too small (fat finger problem)
- No visual distinction between interactive and decorative elements
See: references/affordances.md for affordance design patterns.
3. Signifiers
Definition: Signals that communicate where the action should take place.
Key insight: Affordances determine what's possible. Signifiers communicate where and how.
If affordances are what you CAN do, signifiers show you HOW to do it.
Types:
| Type | Definition | Example |
|---|---|---|
| Deliberate signifier | Designed to communicate | "Push" label on door, placeholder text |
| Accidental signifier | Unintentional but informative | Worn path in grass (people walk here) |
| Social signifier | Other people's behavior | Line of people indicates entrance |
Digital signifiers:
| Signifier | What It Communicates | Example |
|---|---|---|
| Cursor change | This is interactive | Pointer → hand on links |
| Hover state | This responds to interaction | Button color change on hover |
| Placeholder text | What to type here | "Enter your email..." |
| Icons | Function of the element | Magnifying glass = search |
| Labels | What this control does | "Submit", "Cancel", "Next" |
| Color | Status or category | Red = error, green = success |
| Position | Relationship and hierarchy | Close button in top-right corner |
Design rule: When in doubt, add a signifier. It's better to over-communicate than to leave users guessing.
See: references/signifiers.md for signifier patterns and examples.
4. Mappings
Definition: The relationship between controls and their effects.
Natural mapping: When the spatial layout of controls matches the layout of the thing being controlled.
Examples:
| Mapping Quality | Example | Why It Works/Fails |
|---|---|---|
| Natural | Steering wheel turns car direction | Direct spatial correspondence |
| Natural | Volume slider (up = louder) | Matches mental model |
| Poor | Light switch panel (which switch = which light?) | No spatial correspondence |
| Poor | Stovetop controls in a row (which knob = which burner?) | Layout doesn't match |
Digital mapping principles:
- Controls should be near what they affect
- Layout of controls should mirror layout of content
- Direction of action should match expectation (scroll down = content moves up)
- Grouping related controls together
Mapping techniques:
| Technique | How It Works | Example |
|---|---|---|
| Proximity | Control near target | Edit button next to content |
| Spatial | Layout mirrors real world | Map controls match compass directions |
| Cultural | Follows conventions | Red = stop/danger, green = go/safe |
| Sequential | Follows natural order | Steps 1, 2, 3 from left to right (or top to bottom) |
See: references/mappings.md for mapping analysis exercises.
5. Constraints
Definition: Limiting the possible actions to prevent errors.
Four types of constraints:
| Type | Mechanism | Example |
|---|---|---|
| Physical | Shape/size prevents wrong action | USB plug only fits one way (USB-C both ways) |
| Cultural | Social norms guide behavior | Red means stop, green means go |
| Semantic | Meaning restricts options | A rearview mirror only makes |