Interaction Design

Guide for designing intuitive, responsive, and accessible user interactions.

Output Contract

For interaction specifications, structure your response as:

## Interaction Spec: [Component Name]

### States
| State | Visual Treatment | Transition |
|-------|------------------|------------|
| Default | [appearance] | — |
| Hover | [changes] | 150ms ease-out |
| Focus | [focus ring/outline] | immediate |
| Active | [pressed appearance] | 50ms |
| Disabled | [muted appearance] | — |
| Loading | [skeleton/spinner] | [timing] |

### Keyboard
- Tab: [focus behavior]
- Enter/Space: [activation]
- Escape: [dismissal behavior]
- Arrows: [navigation, if applicable]

### Motion
- Duration: [timing in ms]
- Easing: [curve name]
- Reduced motion: [fallback behavior]

### Accessibility
- Focus indicator: [visible, high-contrast description]
- Screen reader: [announcements, aria-labels]
- Touch target: [minimum size]

### Edge Cases
- [Scenario]: [behavior]

For flow/journey analysis:

## Flow Analysis: [Journey Name]

### Steps
1. [Step] → [Expected interaction]

### Friction Points
- [Issue]: [recommendation]

### Missing States
- [State that needs design]

Core Principles

Feedback & Responsiveness

• Every user action deserves acknowledgment (visual, auditory, or haptic)
• Response time expectations: instant (<100ms), fast (<1s), or progress indication
• Optimistic UI: update immediately, reconcile errors gracefully
• Skeleton screens > spinners for perceived performance

Progressive Disclosure

• Show only what's needed at each step
• Reveal complexity gradually through interaction
• Use sensible defaults; make advanced options discoverable
• Reduce cognitive load by chunking information

Direct Manipulation

• Objects should feel tangible and respond to interaction
• Maintain visible connection between action and result
• Support undo/redo for reversible actions
• Provide clear affordances for interactive elements

Consistency & Standards

• Follow platform conventions (web, iOS, Android)
• Maintain internal consistency across the application
• Use familiar patterns before inventing new ones
• Ensure predictable behavior across similar components

Micro-Interactions

State Transitions

• Hover: 150-200ms ease-out for color/shadow changes
• Focus: Immediate visible indicator (outline, ring)
• Active/Pressed: Scale down slightly (0.95-0.98) or darken
• Disabled: Reduced opacity (0.5-0.6), cursor: not-allowed
• Loading: Pulsing skeleton, spinner, or progress bar

Animation Timing

• Micro: 100-200ms (button states, toggles)
• Small: 200-300ms (dropdowns, tooltips)
• Medium: 300-400ms (modals, panels)
• Large: 400-600ms (page transitions, complex reveals)
• Use ease-out for entering, ease-in for exiting

Easing Functions

• ease-out: Elements entering view (feels welcoming)
• ease-in: Elements leaving view (feels decisive)
• ease-in-out: Elements moving within view
• spring: Natural, playful interactions

User Flow Design

Navigation Patterns

• Maintain user's mental model of location
• Provide escape hatches (back, cancel, close)
• Support both linear and non-linear navigation
• Preserve state when navigating away and returning

Onboarding

• Defer account creation until value is demonstrated
• Use progressive onboarding over tutorial dumps
• Highlight features contextually when relevant
• Allow skipping with graceful degradation

Error Recovery

• Prevent errors through constraints and validation
• Inline validation at the right moment (not too eager)
• Clear error messages: what happened, why, how to fix
• Preserve user input during error states
• Offer recovery actions, not just error descriptions

Empty States

• Explain what belongs here and how to add it
• Provide clear call-to-action
• Use illustration/imagery to reduce starkness
• Consider first-run vs. cleared vs. no-results states

Component Behaviors

Forms & Inputs

• Label always visible (not just placeholder)
• Validate on blur, re-validate on change after error
• Show character counts for limited fields
• Auto-focus first field; support tab navigation
• Disable submit during processing; show progress

Modals & Dialogs

• Trap focus within modal
• Close on Escape key and backdrop click (when appropriate)
• Return focus to trigger element on close
• Prevent background scrolling
• Stack modals carefully (avoid when possible)

Dropdowns & Menus

• Open on click (not hover) for accessibility
• Support keyboard navigation (arrows, Enter, Escape)
• Highlight current selection
• Position to avoid viewport edges
• Close on outside click or Escape

Drag & Drop

• Clear visual indication of draggable items
• Ghost/preview during drag
• Valid drop zones highlighted
• Animate items into new positions
• Provide keyboard alternative

Accessibility Patterns

Keyboard Navigation

• All interactive elements focusable via Tab
• Logical focus order matching visual layout
• Skip links for repetitive navigation
• Arrow keys for related controls (tabs, menus)
• Enter/Space for activation; Escape for dismissal

Screen Readers

• Semantic HTML as foundation
• ARIA labels for icon-only buttons
• Live regions for dynamic content
• Announce loading states and completions
• Meaningful link/button text (not "click here")

Motion & Vestibular

• Respect prefers-reduced-motion
• Provide alternatives to motion-based interactions
• Avoid parallax and excessive animation
• Allow pausing auto-playing content

Color & Contrast

• Don't rely on color alone for meaning
• Minimum 4.5:1 contrast for text
• 3:1 for large text and UI components
• Test with color blindness simulators

Loading & Progress

Loading States

• Immediate feedback that action was received
• Skeleton screens for predictable layouts
• Spinners for unpredictable durations
• Progress bars when duration is known
• Stagger skeleton animations for natural feel

Optimistic Updates

• Update UI immediately on user action
• Sync with server in background
• Handle conflicts gracefully
• Rollback with clear explanation on failure

Streaming & Incremental

• Show content as it arrives
• Maintain scroll position during updates
• Indicate when more content is loading
• Handle connection interruptions

Theoretical Foundations

This skill draws from foundational interaction design research:

Direct Manipulation

The principles in this skill build on Shneiderman's direct manipulation framework:

• Visibility of objects of interest
• Rapid, reversible, incremental actions
• Replacement of command syntax with direct object manipulation

See: Direct Manipulation - A Step Beyond Programming Languages.md

Instrumental Interaction

Beaudouin-Lafon's model extends direct manipulation to post-WIMP interfaces, framing interaction as mediated by "instruments" (tools) that operate on domain objects.

See: Instrumental Interaction - an interaction model for designing post WIMP user interfaces.md