diff --git a/assets/256x256.png b/assets/256x256.png
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--- /dev/null
+++ b/assets/256x256.png
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+version https://git-lfs.github.com/spec/v1
+oid sha256:a9bf1cc2403c3a32e7a6f5d5829bb065573922dc050ae2fdb8b3d34b4c87ecf5
+size 8296
diff --git a/assets/300x300.png b/assets/300x300.png
new file mode 100644
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--- /dev/null
+++ b/assets/300x300.png
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+version https://git-lfs.github.com/spec/v1
+oid sha256:6990a598379c457442345e50c3f056c4598a121523bc10980835c08fc7447a54
+size 10119
diff --git a/assets/300x300.svg b/assets/300x300.svg
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+version https://git-lfs.github.com/spec/v1
+oid sha256:432198e63fa9676541a41436917e025d1ea6af3772139c1dea450fcc0155cfd0
+size 13054
diff --git a/assets/50x50.png b/assets/50x50.png
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+++ b/assets/50x50.png
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+version https://git-lfs.github.com/spec/v1
+oid sha256:fe3b5b8bf9c32e57c0af366c455b11ae68eb9fb8a32f371c9c445b3e7e89cc02
+size 1120
diff --git a/assets/64x64.png b/assets/64x64.png
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--- /dev/null
+++ b/assets/64x64.png
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+version https://git-lfs.github.com/spec/v1
+oid sha256:f68df7bae94eb4c4cddfa6af47d7819d01a6482d4f6afe6ef3236f72f9adf15f
+size 1523
diff --git a/assets/LICENSE.txt b/assets/LICENSE.txt
new file mode 100644
index 0000000..7c03569
--- /dev/null
+++ b/assets/LICENSE.txt
@@ -0,0 +1 @@
+This work is licensed under CC BY-SA 4.0. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/4.0/
diff --git a/assets/README.md b/assets/README.md
new file mode 100644
index 0000000..2d3da34
--- /dev/null
+++ b/assets/README.md
@@ -0,0 +1,75 @@
+# the logo
+
+Some different sizes' logos are needed.
+
+## license
+
+
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
+
+## the process of creation
+
+No professional designers are here. Thus the following steps involve many programer styles. :-)
+
+1. use excalidraw and export png and svg.
+
+ ```bash
+ # results
+ logo.excalidraw
+ logo.png
+ logo.svg
+ ```
+
+2. manually edit the `logo.svg` and make background transparent.
+
+ ```bash
+ # results
+ logo-transparent.svg
+ ```
+
+3. use python library [`svgutils`](https://github.com/btel/svg_utils) to make a strictly square figure. The [doc](https://svgutils.readthedocs.io/en/latest/tutorials/composing_multipanel_figures.html) is very useful.
+
+ ```python
+ from svgutils.compose import *
+ def get_standard_300x300(file_name):
+ fig = Figure(300, 300,
+ Panel(
+ SVG(file_name),
+ ).move(-3, 12),
+ )
+ return fig
+
+ get_standard_300x300('logo-transparent.svg').save('300x300.svg')
+
+ # def get_other_size_from_standard(file_name, px):
+ # fig = Figure(px, px,
+ # Panel(
+ # SVG(file_name).scale(px/300.0),
+ # ).move(-3*px/300.0, 12*px/300.0),
+ # )
+ # return fig
+
+ # get_other_size_from_standard('logo.svg',256).save('256x256.svg')
+ ```
+
+ ```bash
+ # results
+ 300x300.svg
+ ```
+
+4. use `inkscape` command line to get different sizes' `.png` files.
+
+ ```bash
+ inkscape 300x300.svg -o 300x300.png
+
+ inkscape 300x300.svg -o 50x50.png -w 50 -h 50
+
+ inkscape 300x300.svg -o 64x64.png -w 64 -h 64
+ inkscape 300x300.svg -o 256x256.png -w 256 -h 256
+ ```
+
+ ```bash
+ # results
+ 50x50.png
+ 64x64.png
+ 256x256.png
+ ```
diff --git a/assets/logo-transparent.svg b/assets/logo-transparent.svg
new file mode 100644
index 0000000..c9f97eb
--- /dev/null
+++ b/assets/logo-transparent.svg
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+version https://git-lfs.github.com/spec/v1
+oid sha256:daedd262170200cb5e8cc288898b40892771b3962cf2bc17dc443f1c82a4aa94
+size 12886