Fun Calc 🎮

A wildly unconventional calculator where each theme is a completely different experience — not a reskin, but a unique visual world rendered on canvas with PixiJS. Built with Rust + Tauri backend and vanilla JS.

---

Screenshots

View all themes

Theme	Preview
Matrix
Odontology
Dragon

---

Themes

Every theme is a full PixiJS canvas application — its own UI, its own interaction model, its own visual language. They share only the math engine.

Theme	How It Works
Matrix 🟢	No buttons. 16 columns of falling characters fill the screen — each column rains a single digit (green), operator (red), = (white), or C (dim). Click a column to grab its character — the column freezes, the character flies to the display. Hover a column to highlight it. Press the = column and all rain accelerates wildly, freezes white, then the answer types out character by character.
Odontology 🦷	An open mouth with gums, lips, and tongue. Upper teeth are digit buttons (molars, canines, incisors — shaped like real teeth). Lower teeth are operators. Click a tooth and it vibrates with drill sparks. Results appear on an X-ray light panel. Errors cause cavities — teeth darken and crack. AC triggers a polish sweep.
Dragon 🐉	A dark cave with a dragon's treasure hoard. Gold coins have numbers embossed on them — click one and it flips and flies to the display. Operators are glowing rune stones. A cauldron sits in the center — press it to brew your calculation. Fire erupts from the cauldron on equals. Big results trigger a dragon flyby across the screen leaving a fire trail.

---

Getting Started

Browser Mode (no Rust needed)

cd src
python3 -m http.server 1420
# Open http://localhost:1420

Requires internet for PixiJS CDN on first load.

Desktop App (Rust + Tauri)

# Prerequisites: Rust 1.70+, Node.js
cd src-tauri
cargo tauri dev

Build for Production

cd src-tauri
cargo tauri build
# Output: src-tauri/target/release/bundle/

---

Architecture

src/
  index.html          Menu + canvas container (minimal HTML)
  engine.js           Calculator engine — pure math logic, no DOM (State Machine)
  audio.js            Web Audio API sound effects
  pixi-base.js        PixiTheme base class — shared engine wiring (Strategy)
  theme-matrix.js     Matrix theme — rain, flying digits, cascade
  theme-odonto.js     Odontology theme — mouth, teeth, drill sparks, X-ray
  theme-dragon.js     Dragon theme — coins, runes, cauldron, fire
  app.js              Menu rendering + theme lifecycle (Mediator)
  style.css           Menu styles only (themes render on canvas)

src-tauri/
  src/
    main.rs           Tauri app bootstrap
    engine.rs         Formatting, scientific functions, constants (48 tests)
    parser.rs         Tokenizer + recursive-descent evaluator (26 tests)
    commands.rs       Tauri command handlers (thin wrappers)
  Cargo.toml
  tauri.conf.json

tests/
  engine.test.js      180 unit tests for the JS calculator engine

How Themes Work

Each theme extends PixiTheme and implements 5 methods:

Method	Purpose
_buildScene()	Creates all PixiJS display objects (the entire UI)
_updateDisplay(expr, display)	Renders the current expression and result
_onResult(result)	Animates a successful calculation
_onError(message)	Animates an error
_onClear()	Animates a reset

The base class handles engine integration, audio, and helper animations (tween, flyTo). Themes handle their own click events and call this.digit(), this.op(), this.equals(), etc.

Design Patterns

• State Machine — Calculator engine alternates between INPUT and RESULT phases
• Strategy — Each theme implements the same interface with completely different rendering
• Mediator — app.js coordinates menu, theme lifecycle, and keyboard events
• Template Method — PixiTheme defines the skeleton; subclasses fill in the specifics

---

Testing

JavaScript (180 tests)

node tests/engine.test.js

Covers: tokenizer, expression evaluator (precedence, parens, unary, edge cases), number formatting, scientific functions, constants, full calculator state machine (chaining, trailing operators, repeated equals, parentheses, sign toggle, decimal input, multi-digit, negative numbers, history cap, error recovery, backspace edge cases).

Rust (74 tests)

cd src-tauri
cargo test

# Or run modules standalone (no network needed):
rustc --edition 2021 src/parser.rs --test -o /tmp/parser_test && /tmp/parser_test
rustc --edition 2021 src/engine.rs --test -o /tmp/engine_test && /tmp/engine_test

Covers: tokenizer, recursive-descent parser, operator precedence, parentheses, scientific functions, domain errors, number formatting edge cases.

---

Contributing

See CONTRIBUTING.md for guidelines on adding new themes.

Security

See SECURITY.md for reporting vulnerabilities.

Code of Conduct

See CODE_OF_CONDUCT.md.

License

MIT