Markup
Plain HTML interface
The UI is defined in one HTML page, including the currency toggles, keypad modal, info panel, help modal, and dynamic display areas for BTC, SATS, and fiat conversions.
Main Stack
What powers this Bitcoin conversion tool and what makes it more feature-rich than a basic static page.
Styling
Custom CSS
The visual system is custom-built and includes branded styling, responsive behavior, mobile-first keypad support, icon assets, and dark mode support.
JavaScript structure
Core + app split
The project separates lower-level conversion logic from UI orchestration. That keeps pricing, formatting, translation, interaction, and display logic more maintainable than a one-file script.
Live data
External Bitcoin price API
The app uses live price data for conversions and price-change tracking, so it is still static in structure but depends on an external market data source for full functionality.
User experience
Multi-language and mobile features
The calculator supports English and Portuguese, includes Android-specific handling, a custom keypad flow, dark mode logic, and richer modal/help interactions than a minimal utility page.
BTC amounts are also displayed with thin-space grouping across the eight decimal places (e.g. 1.23 456 789), making sat-level values easier to read at a glance.
Runtime model
No bundler or framework
The project has no package manifest or frontend framework. It stays dependency-light by relying on browser JavaScript, local assets, and a small set of manually organized script files.
How It Runs
The calculator combines static assets with runtime market data inside the browser.
1
The browser loads the static app shell
index.html loads the core interface, icon assets, modal structures, and the JavaScript entry files.
2
Core logic initializes conversion behavior
js/core.js handles currency logic, display formatting, translation data, and calculator behavior shared across the app.
3
App logic wires the UI
js/app.js coordinates animations, info panels, dark mode, Android input handling, and the interactive flow around the displays and modals.
4
Live market data updates the dashboard
The app fetches Bitcoin pricing from an external source and uses it to compute BTC/SATS and fiat equivalents, along with change-period displays.
5
User state stays in the browser
Interactions such as language choice and dark mode preference are handled locally, keeping the app lightweight while still feeling dynamic.
Architecture Map
The project is static, but it is organized more like a small hand-built application than a single-file toy page.
Key files
index.htmlMain UI, modal markup, asset loading, and script entry points.
css/styles.cssAll styling, layout, responsiveness, and visual modes.
js/core.jsCore conversion logic, translation dictionary, and formatting behavior.
js/app.jsUI interaction, modal/panel behavior, dark mode, and mobile-specific logic.
assets/Brand and interface assets like icons and imagery.
archive/Previous or experimental versions kept for reference.
Architecture Analysis
index.html css/styles.css js/core.js js/app.js assets/ archive/
This is a good example of a project that is still “plain HTML/CSS/JS,” but has enough interaction depth that it behaves like a small product rather than a basic static page.
Data and Storage
The app blends live price data with browser-only preferences and interaction state.
External data
Market pricing comes from an API
The calculator uses live Bitcoin price information rather than only fixed inputs.
Currency conversion depends on that market data being available.
The price view includes change tracking across multiple time windows.
This makes the project more dynamic than an offline-only static calculator.
Local interaction state
Preferences stay in the browser
Language preference is handled locally.
Dark mode state is persisted in localStorage.
Android-specific and keypad behavior are handled client-side.
No account, backend persistence, or database is required.
Run Commands
The app can be opened directly or served with any tiny static server.
Local usage
open index.html # or python -m http.server
The README recommends serving it with a small local server, but the project itself has no package install step or build process.
Environment setup
What the project expects
No package manager setup.
No framework runtime.
No environment variables.
Network access is needed for live BTC pricing.
Bottom Line
BTC Calculator is a browser-first static app built with HTML, CSS, and modular vanilla JavaScript, but it goes beyond a simple static utility by incorporating live Bitcoin market data, multilingual UI, dark mode, and mobile-specific interaction handling.