Update README.md

README.md

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 # two-layer-qrcode
 
+Live demo: [https://yuantailing.github.io/two-layer-qrcode/](https://yuantailing.github.io/two-layer-qrcode/)
+
+Note that the demo is deployed on [AWS Lambda](https://aws.amazon.com/lambda/), thus it's slower than the reported result in the paper.
+
 ## Usage
 
 ```sh
@@ -8,3 +12,19 @@ $ make -C qrmerge  # please be patient to wait
 $ # put a logo to qrmerge/logo.png as the default logo
 $ FLASK_APP=app.py python3 -m flask run --with-threads
 ```
+
+## System requirements
+
+OS:
+
+- Windows / Linux / macOS
+
+Software:
+
+- Python 3
+- MinGW / g++
+
+Memory:
+
+- Compile: (don't know)
+- Run: 256 MB