Single-file app starter

Why a starter file, and not just "write some HTML"?

An HTML file that looks fine in a desktop browser can look wrong the moment it is bundled into an Android app, and the reasons are always the same few lines. Without a viewport meta tag, WebView renders the page at 980px wide and shrinks it, so the text is unreadably small. Without viewport-fit=cover and safe-area padding, the top of the page sits under the status bar on phones with a notch. Without overscroll-behavior:none the page bounces like a web page rather than sitting like a screen. Without touch-action:manipulation every tap waits 300ms in case it is a double-tap.

None of this is hard; it is just easy to forget. The starter writes the head that an APK needs and gives you a layout you can delete — a header and cards, three tabbed screens, a searchable list, or nothing at all.

What is in the generated file

• The viewport line, with viewport-fit=cover so the page can extend under the system bars and pad itself with env(safe-area-inset-*).
• theme-color, which the builder can read to colour the status bar, and color-scheme so form controls match your light or dark choice.
• System font stack. No web fonts, because a bundled app should not depend on a connection to look right. Roboto on Android, San Francisco on iOS previews, Segoe on Windows.
• CSS variables for the accent, background, text and card colours at the top of the stylesheet, so restyling is one line each.
• A localStorage helper (optional): save(key, value) and load(key, fallback), because a bundled app has no server and this is where its state lives. Data persists across app restarts and is removed when the app is uninstalled.
• No external requests. Nothing in the file points at a CDN, an API or a font server, so it works in airplane mode on day one.

From this file to an installed app

1. Download index.html, open it in Chrome, resize the window to phone width and check it.
2. Add your content. Keep everything in the one file, or split it into style.css and app.js and ZIP the folder — the folder-structure guide explains the rules for paths.
3. Upload the file (or the ZIP) in the builder, set a name and an icon, and build. The APK downloads in a few minutes and installs on any Android phone.