Is this the official PrismCraft site?

No. Official playable build is on itch.io.

Is PrismCraft a Minecraft modpack?

No. It is a standalone HTML5 prototype. Unrelated to Prism Launcher and to Minecraft servers named PrismCraft.

https://lairhisson.itch.io/prismcraft

No. Browser on itch, or the zip.

Three steps from the official itch.io page. No keybinds guessed here.

Play on itch.io Original geometric illustration of triangular prisms

Open the official itch.io page

Open https://lairhisson.itch.io/prismcraft

Go to https://lairhisson.itch.io/prismcraft — the official PrismCraft prototype by LAirHisson.
Run it in the browser

Click Run game (HTML5 in the browser), or download Build Prismcraft 0.3.zip

On the itch.io page, click Run game to play the HTML5 build in your browser. You can also download Build Prismcraft 0.3.zip.
Play the prototype

Play the prototype. This site is an unofficial guide.

Explore the triangular-prism world. This is an unofficial guide. PrismCraft is a prototype, not Minecraft and not a modpack.

Is this the official PrismCraft site?: No. Official playable build is on itch.io.
Is PrismCraft a Minecraft modpack?: No. It is a standalone HTML5 prototype. Unrelated to Prism Launcher and to Minecraft servers named PrismCraft.
Where do I play?: https://lairhisson.itch.io/prismcraft
Do I need Minecraft?: No. Browser on itch, or the zip.