This is impressive! Perhaps this is because I’m from an English-speaking country, but I believe even in the real Criterion Closet, the spine title text orientation is top-to-bottom, rather than bottom-to-top.
There's a more-recent post on the same blog that gets into the details of how they're using the WebAuthn PRF extension to store key material, but for platforms and browsers that don't yet support the extension, you'll need a password manager that does. There's a table midway down the post with details: https://confer.to/blog/2025/12/passkey-encryption/