diff --git a/README.md b/README.md
index 30148c9547e9aa1a5bde89235325ea633ad62564..60e4f195989c38ba2454a38c3ab7f1cbf2a9c6b3 100644
--- a/README.md
+++ b/README.md
@@ -35,8 +35,7 @@ sh -c "$(curl -fsSL https://csst-tb.bao.ac.cn/code/csst-l1/csst_proto/-/raw/main
 A simple example on how to use this package:
 
 ```python
-import numpy as np
-from csst_proto.top_level_interface import flip_image, read_test_image
+from csst_proto.top_level_interface import flip_image
 from astropy.io import fits
 
 # read an L0 image
@@ -69,22 +68,29 @@ The `csst_proto` uses an awesome algorithm based on `numpy.ndarray` indices to f
 | `setup.py`         | sphinx-based documentation      | 鈭氣垰     | 鈭�   |     |
 
 ## important stages
-
-1. **installation**: `source code` & `setup.py` -> `pip install <package_name>`
-2. **a simple guide**: `README.md`
-3. **unittest**: `pytest`
-4. gitlab CI/CD pipeline: `.gitlab-ci.yml`
-5. sphinx-based documentation: `doc/` & `readthedocs.yml`
+1. **code**, **code style** & `top_level_interface`
+2. **installation**: `source code` & `setup.py` -> `pip install <package_name>`
+3. **a simple instruction**: `README.md`
+4. **unittest**: `pytest`
+5. *gitlab CI/CD pipeline: `.gitlab-ci.yml`
+6. *sphinx-based documentation: `doc/` & `readthedocs.yml`
 
 ## useful links
-
-- git: https://git-scm.com/
+- python packaging user guide: https://packaging.python.org/en/latest/
+- packaging binary extensions (C/C++): https://packaging.python.org/en/latest/guides/packaging-binary-extensions
+- `setuptools`: https://packaging.python.org/en/latest/tutorials/installing-packages/
+- recommended IDEs
+  - PyCharm: https://www.jetbrains.com/pycharm/
+  - VS Code: https://code.visualstudio.com/
+- `git`: https://git-scm.com/
   - Pro Git: https://git-scm.com/book/en/v2
 - Numpydoc: https://numpydoc.readthedocs.io/en/latest/format.html
   - for C: https://peps.python.org/pep-0007/
   - for Python: https://peps.python.org/pep-0008/
-- unittest: https://docs.python.org/3.8/library/unittest.html
-- sphinx: https://www.sphinx-doc.org/en/master/index.html
+- `unittest`: https://docs.python.org/3.8/library/unittest.html
+- gitlab CI/CD pipeline: https://docs.gitlab.com/ee/ci/pipelines/
+- gitlab runners: https://docs.gitlab.com/runner/
+- `sphinx`: https://www.sphinx-doc.org/en/master/index.html
+- markdown: https://www.markdownguide.org/
 - restructured text: https://docutils.sourceforge.io/rst.html
-- readthedoc: https://readthedocs.io/ or https://rtfd.io/
-- 
\ No newline at end of file
+- readthedocs: https://readthedocs.io/ or https://rtfd.io/