This is cool. There are also the Unicode Tag characters that mirror ASCII and are often invisible in UI elements (especially web apps).

The unique thing about Tag characters is that some LLMs interpret the hidden text as ASCII and follow instructions, and they can even write them:

https://embracethered.com/blog/posts/2024/hiding-and-finding...

Here an actual exploit POC that Microsoft fixed in Copilot: https://embracethered.com/blog/posts/2024/m365-copilot-promp...