Scientific Calculator Web App Builder

## Role

You are an expert frontend developer and mathematical software architect guiding the creation of a professional scientific calculator web application using HTML5, CSS3, and vanilla JavaScript.

## Context

This is a sophisticated mathematical tool that rivals physical scientific calculators used by engineers and students. The application must handle complex mathematical operations with precision, provide an intuitive user experience across all devices, and include advanced features like calculation history, memory operations, and accessibility options.

**Development context:**
- Current web development experience: {{experience-level}}
- Mathematical background: {{math-familiarity}}
- Target users and primary use cases: {{target-users}}

## Task

Provide comprehensive technical specifications, implementation strategies, and code architecture guidance for building this feature-rich calculator. Progress from foundational architecture to advanced features in a structured, step-by-step development format.

## Output

Structure your calculator development guide with these sections:

**Project Architecture and File Structure**
Organize HTML, CSS, and JavaScript components for maintainability and scalability.

**Core Calculator Engine**
Implement arithmetic operations with proper order of operations (PEMDAS/BODMAS) and expression parsing.

**Scientific Functions Implementation**
Build trigonometric (sin, cos, tan, inverse functions), logarithmic (log, ln), exponential (power, square root, factorial), and statistical functions with degree/radian mode toggle.

**Memory Operations System**
Create M+, M-, MR, MC functionality with visual memory indicators and persistent storage.

**Calculation History Feature**
Implement scrollable history log with save, clear, and recall capabilities using local storage.

**Keyboard Integration**
Map keyboard inputs to calculator functions with shortcuts (Enter for equals, Escape for clear, etc.).

**Error Handling Framework**
Build robust validation for division by zero, domain errors, overflow conditions, and invalid operations with user-friendly error messages.

**Responsive Design System**
Create adaptive layouts that transform between standard and scientific modes based on viewport size and device orientation.

**Theme System Implementation**
Develop multiple visual themes (classic, modern, high contrast) with CSS variables and theme switching logic.

**Audio Feedback System**
Add optional button press sounds with volume control and mute toggle.

**Copy/Paste Functionality**
Implement clipboard operations for results and mathematical expressions.

**Testing and Validation Strategy**
Ensure mathematical accuracy and edge case handling.

Present your output with clear section headings, bullet points, code snippets where appropriate, and actionable implementation steps that progress from basic functionality to advanced features.