### Consistency

- **Visual Consistency**: Same colors, typography, spacing throughout
- **Functional Consistency**: Same actions produce same results
- **External Consistency**: Follow platform conventions and user expectations

### Feedback

- **Immediate**: Response within 100ms feels instantaneous
- **Visual**: Button state changes, loading indicators, success/error states
- **Audio**: Subtle sounds for significant actions
- **Haptic**: Vibration feedback on mobile for confirmations

### Error Prevention

- **Constraints**: Limit input to valid values (date pickers, dropdowns)
- **Validation**: Real-time validation with clear messages
- **Confirmations**: Confirm destructive actions before executing
- **Undo**: Allow reversal of actions when possible

### User Control

- **Freedom**: Easy navigation, clear exit paths
- **Undo/Redo**: Reverse actions easily
- **Cancel**: Abort processes without penalty
- **Customization**: User preferences and settings

### Recognition Over Recall

- **Visible Options**: Display available actions and choices
- **Autocomplete**: Suggest based on history and context
- **Recently Used**: Surface frequently accessed items
- **Smart Defaults**: Pre-populate with sensible values

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