Calculator — implement UI, operations, and keyboard support #161

Project slug (e.g., snake, todo)

calculator

Summary

Build the calculator MVP using vanilla JS. Provide a display, a button grid, click handlers, and full keyboard support.

Details / Acceptance criteria

Acceptance Criteria:

• Supports +, −, ×, ÷, =, ., AC (clear), CE/backspace, +/- (sign), %.
• Prevents multiple decimals in a number.
• Gracefully handles divide-by-zero.
• Reasonable float rounding (e.g., 10–12 significant digits).
• Keys 0–9, + - * / . Enter/Return, Escape (AC), Backspace (CE) work.
• Responsive layout; display truncates/scrolls without breaking.

Files:

• projects/calculator/index.html
• projects/calculator/styles.css
• projects/calculator/main.js

Tasks:

• Build display + grid layout.
• Wire button clicks and keyboard events.
• Implement operation state machine (current, previous, operator).
• Add formatting/rounding helpers.
• Add ARIA labels and focus styles.

Scope

• UI changes
• Logic changes
• Accessibility
• Tests (manual)