Specification

Draft 1. An .applet is a zip of static web files plus a manifest.json. Appverse unpacks it in the browser and runs it in a locked-down sandbox.

Manifest

Field	Required	Meaning
`applet`	yes	Format version, currently `1`.
`id`	yes	Reverse-domain id, e.g. `com.example.notes`.
`title`, `author`, `version`	yes	Shown on the permission card.
`entry`	yes	HTML file to load, normally `index.html`.
`width`, `height`	no	Preferred frame size in CSS pixels.
`permissions`	no	List from the table below. Shown to the user before the app runs.

Permission	Gives the app
`storage`	`appverse.storage.get/set/remove`, a per-app key-value store kept in the visitor's browser.
`fullscreen`	Ability to ask for fullscreen, on a user gesture.
`clipboard`	Write to the clipboard, on a user gesture.
`network` (planned)	Requests to an allowlist of hosts declared in the manifest and shown to the user.

The package is read and unpacked in the browser; nothing is uploaded. The zip reader rejects path traversal, duplicate names, encrypted or zip64 entries, bad CRCs, entries larger than declared, and packages over the file-count and size caps.
The app runs in <iframe sandbox="allow-scripts">, with no allow-same-origin, popups or top navigation, so it has an opaque origin and cannot touch the host page, cookies or storage.
In production the frame is served from a separate origin (for example *.appverse-apps.lol) so a sandbox escape does not reach the main site.
Appverse rewrites the entry HTML on load and inserts a CSP <meta> as the first element of <head>:
```
default-src 'none'; script-src 'unsafe-inline'; style-src 'unsafe-inline'; img-src data: blob:;
media-src data: blob:; font-src data:; worker-src blob:; connect-src 'none'; frame-src 'none';
form-action 'none'; base-uri 'none'
```
The package's files are inlined into that one document: scripts and stylesheets become inline code, and images, fonts and media become data: URLs. A reference to anything outside the package (http:, //host) or to a missing file is an error. Bundle your JavaScript into plain scripts: ES module import of other files does not work. A package whose HTML already has a CSP meta tag is rejected.
The only way out is a small postMessage bridge, gated by the manifest permissions.

An app can use a lot of CPU or memory. Stop destroys the frame.
An app can show misleading content, such as a fake sign-in form. The frame is labelled as untrusted, and the player says never to enter passwords. Only run apps from people you trust.
CSP and sandbox behaviour differ slightly between browsers, so the test suite checks the escape routes (fetch, images, CSS url(), forms, WebRTC, sendBeacon, popups, navigation) in each engine.