Simple neon / pixel styled calculator you can open by just double‑clicking index.html. No build tools, no frameworks.

Goal: look cool, stay readable, be easy to explain in an interview.

https://retro-calculator.ankankun.me/

Desktop view:

Mobile view:

• Basic math: + − × ÷
• Extra: percent %, change sign (±), clear (AC)
• Decimal numbers
• Keyboard support (0‑9 . + - * / Enter = Esc)
• Shows the full operation when you press =
• Live IST clock at the bottom
• Mobile friendly (shrinks buttons on very narrow screens)

State variables in script.js:

current   -> string shown on the green main display (starts '0')
previous  -> stored number after you pick an operator
operator  -> '+', '-', '*', '/' (null when none selected)
justCalculated -> true right after '=' so next number replaces result

Flow:

1. Press numbers -> they append to current (unless we just finished a calc).
2. Press an operator -> move current into previous, store operator, reset current to '0'.
3. Press more numbers -> build second number.
4. Press '=' -> compute with previous + operator + current, show result, clear previous + operator, flag justCalculated.
5. Chain operations: if you press another operator instead of '=', we quickly run equals() then continue.
6. Percent = divide current by 100. Sign = toggle leading -.
7. Divide by zero -> shows ERR (very basic error handling).

Formatting helper: trimResult() keeps numbers from overflowing by shortening long outputs or using scientific notation for huge values.

• Only simple color variables kept (easier to tweak). Removed spacing & font size CSS variables to look less “tool generated”.
• Pixel font: Google Fonts Press Start 2P.
• Scanline effect: a pseudo element with a repeating linear gradient.
• Neon glow: stacked box‑shadows around buttons.
• Layout: plain CSS Grid for buttons (repeat(4, 1fr)), no frameworks.

• Container width capped at 384px (classic small handheld size feel).
• At < 360px screen width: smaller font + smaller button padding.

• Memory keys (M+, M-, MR, MC)
• Backspace (delete last digit)
• History panel
• Better error handling (flash screen, etc.)
• Limit significant digits more intelligently
• Theme toggle (bright vs dark neon)

Updated every second. Uses toLocaleString with timeZone:'Asia/Kolkata' so it shows IST regardless of the user’s local machine timezone.

Enjoy hacking it. Tweak colors, break it, fix it, learn it. Retro vibe unlocked. 😎