Building upon general usability principles, GUI design has specific considerations:

• Visibility and Feedback: Users should always know what they can do and what is happening. Provide immediate and clear feedback for every action (e.g., button presses, loading states, error messages).
• Consistency: This is paramount.
• Internal Consistency: Uniformity within the application itself (e.g., consistent icons, menu placement, terminology, interaction patterns).
• External Consistency: Adherence to platform conventions (e.g., Windows applications should generally behave like other Windows applications, Android apps like other Android apps).
• Consistency across versions: Maintain consistency when updating an application to reduce relearning.
• Affordances: Design elements should visually suggest their function. A button should look "pushable," a slider "draggable," and a link "clickable."
• Discoverability: Important features and functionalities should be easy for users to find, whether through intuitive navigation, clear labeling, or helpful hints.
• Error Prevention and Recovery: Design to prevent common errors (e.g., disable impossible actions, provide input masks). When errors do occur, provide clear, constructive error messages and easy ways to recover (e.g., undo, cancel, restore).
• Efficiency of Use: Allow experienced users to perform tasks quickly (e.g., shortcuts, customizable interfaces). Minimize steps for frequent actions.
• User Control and Freedom: Give users a sense of agency. Allow them to initiate actions, stop processes, and navigate freely. Provide "undo" and "redo" options.
• Simplicity and Minimalism: Avoid clutter. Present only necessary information at a given time. Every element should serve a purpose. Remove redundant or distracting elements.

Aesthetics, often referred to as visual design, is not just about making things look pretty; it directly impacts usability and user perception. A well-designed aesthetic interface is often perceived as more usable, trustworthy, and professional.

• Visual Hierarchy: Guide the user's eye through the interface. Use differences in size, color, contrast, typography, and spacing to emphasize important elements and create a logical flow of information.
• Example: Larger, bolder text for headings; contrasting colors for call-to-action buttons.
• Layout and Grid Systems: Organize elements on the screen in a structured and harmonious way. Grid systems (e.g., 8-point grid, column grids) provide consistency and help in achieving visual balance, alignment, and rhythm.
• Color Theory: Use color purposefully to convey meaning, evoke emotions, and enhance readability.
• Warm colors (red, orange, yellow): Can convey energy, urgency.
• Cool colors (blue, green, purple): Can convey calm, trust, stability.
• Contrast: Ensure sufficient contrast between text and background for readability.
• Color blind accessibility: Design with consideration for color-blind users.
• Typography: The choice of fonts, their size, weight, line height, and letter spacing significantly impacts readability and the overall aesthetic.
• Serif vs. Sans-serif: Understand when to use each (e.g., sans-serif often preferred for screen readability).
• Font pairing: Combine fonts effectively to create visual interest without clutter.
• Whitespace (Negative Space): The empty space around and between elements. Proper use of whitespace improves readability, reduces cognitive load, and highlights important content. It creates a sense of order and sophistication.
• Imagery and Iconography: Use relevant, high-quality images and clear, universally understood icons. Icons should be consistent in style and easily recognizable.
• Animations and Transitions: Subtle, purposeful animations can provide feedback, guide attention, and make interactions feel smoother and more delightful. Avoid gratuitous or distracting animations.
• Brand Identity: The GUI should reflect the brand's personality, values, and visual language, creating a consistent experience across all touchpoints.

• Buttons: Clear, concise labels; distinct visual states (normal, hover, active, disabled); appropriate size for touch or click targets.
• Text Fields and Forms: Clear labels, helpful placeholder text, input validation (real-time feedback), proper alignment of fields and labels.
• Navigation (Menus, Tabs, Breadcrumbs): Intuitive hierarchy, clear labeling, consistent placement, clear indication of current location.
• Sliders, Checkboxes, Radio Buttons: Clear visual distinction, intuitive interaction.
• Data Displays (Tables, Charts): Readability, organization, clear headings, sorting/filtering options, effective use of visualization to convey data insights.
• Modals/Dialogs: Used sparingly, clear purpose, easy to dismiss, provide context.
• Error Messages: Specific, polite, actionable, and non-accusatory.