To optimize a GUI for low-light or nighttime use:

1. High-contrast colors: Use high-contrast colors like black and white, or dark blue and light gray.

2. Invert colors: Offer an invert colors option to reduce eye strain.

3. Dim or night mode: Implement a dim or night mode that reduces screen brightness.

4. Backlight adjustment: Allow users to adjust backlight settings or auto-adjust based on ambient light.

5. Large font sizes: Provide large font size options for better readability.

6. Simplified layout: Simplify the layout to reduce visual clutter.

7. Reduced color palette: Use a reduced color palette to minimize visual stimulation.

8. Soft lighting effects: Apply soft lighting effects to reduce harshness.

9. Avoid bright colors: Avoid using bright colors that can cause eye strain.

10. Test in low-light conditions: Test the GUI in low-light conditions to ensure usability.

11. Auto-brightness adjustment: Implement auto-brightness adjustment based on ambient light.

12. Screen orientation: Allow users to adjust screen orientation for optimal viewing.

13. Night-friendly icons: Use night-friendly icons that are easily recognizable in low light.

14. Reduced animation: Reduce or disable animations to minimize visual stimulation.

15. User-adjustable settings: Provide user-adjustable settings for personalized comfort.

By implementing these optimizations, you can create a GUI that is comfortable and usable in low-light or nighttime environments.