Calx.js is a spreadsheet calculation engine that brings Excel-like functionality to web applications. It parses and evaluates formulas, manages workbooks/sheets/cells with dependency tracking, and provides both a programmatic API and jQuery plugin interface. The architecture features a modular Workbook→Sheet→Cell hierarchy with modern Chevrotain-based formula parsing, FormulaJS integration for function implementations, and efficient recalculation through dependency tracking. Key entry points include the main Calx class and jQuery plugin wrapper, with data flows proceeding from HTML attribute parsing through formula evaluation to DOM updates.