https://www.nngroup.com/articles/ten-usability-heuristics/

Usability heuristics for user interface design

1. always tell user what the system is doing
2. tell the user in their language, not system’s language, and follow real world convention. (联想拟物化设计，为了模仿物理世界；如今用户习惯培养起来后，改成平面化设计)
3. user control and freedom. Always provide an emergency exit for user. like cancel/redo/undo.
4. prevent user errors. Providing confirmation dialog/undo, put “reply all” button explicitly more separated over other buttons.
5. Minimize the user’s memory load by making objects, actions, and options visible. (recognition requires less memory load than recall)
   1. What is the capital of China? (recall)
   2. Is Beijing the capital of China? (recognition)
6. build accelerator for experienced users, while keep the UI simple, flexible for newbee users.
   1. ctrl + C copy is an accelerator; double click to like a photo is an accelerator.

7. Aesthetic and minimalist design. Keep a high signal-noise ratio. Remove elements in the UI that is distracting/not conveying any information to users.

8. help user recognize, diagnose and recover from the error

• error message should express in plain english text, and let user knows how to recover from the error.

9. help and documentation

10. consistency and standards

• internal consistency
• external consistency
• The goal of the consistency is to reduce users’ cognitive load to learn new things.