Leerzeichen-Entferner

You are an experienced full-stack web developer. Build a web tool called "Leerzeichen-Entferner" that meets the requirements below.

## Goal

Build a tool that cleans up extra spaces, blank lines and line breaks in text.

## Core features

- Trim leading and trailing spaces
- Collapse repeated spaces
- Remove blank lines
- Join lines with spaces
- Handle tabs, non-breaking spaces and full-width spaces

## Inputs

- Text to clean
- Checkboxes for each rule

## Outputs

- Cleaned text
- Number of characters removed

## Edge cases and handling rules

- Option to preserve indentation for code
- Mixed CRLF and LF line endings
- Option to remove zero-width spaces (U+200B)
- Performance on very long text

## Implementation requirements

- Build it as a single page (HTML, CSS, JavaScript) that runs entirely in the browser, and never send the user's input to a server.
- Make the UI responsive and easy to use on mobile; label every input and keep everything keyboard accessible.
- Add a Copy button for results and show clear, friendly error messages for invalid input.
- Keep the core logic in functions separate from the UI so it can be unit-tested.

## Definition of done (test cases)

- '  a   b  ' becomes 'a b'
- Removing blank lines leaves none
- Non-breaking spaces become normal spaces

First outline your implementation plan in at most five lines, then write the complete code, and finally explain how to check the test cases above.

---
name: build-whitespace-remover
description: Use when building or changing a Leerzeichen-Entferner tool. Build a tool that cleans up extra spaces, blank lines and line breaks in text.
---

# Build: Leerzeichen-Entferner

## Goal

Build a tool that cleans up extra spaces, blank lines and line breaks in text.

## Workflow

1. Review the required features, inputs and outputs below and ask about anything missing first.
2. Implement the core logic as pure functions separate from the UI.
3. Check the logic against the test cases in the verification list.
4. Build a responsive UI with an input form, a result area and a Copy button.
5. Reproduce each edge case listed under Rules and refine the error messages.

## Core features

- Trim leading and trailing spaces
- Collapse repeated spaces
- Remove blank lines
- Join lines with spaces
- Handle tabs, non-breaking spaces and full-width spaces

## Inputs

- Text to clean
- Checkboxes for each rule

## Outputs

- Cleaned text
- Number of characters removed

## Rules

- Option to preserve indentation for code
- Mixed CRLF and LF line endings
- Option to remove zero-width spaces (U+200B)
- Performance on very long text
- Build it as a single page (HTML, CSS, JavaScript) that runs entirely in the browser, and never send the user's input to a server.

## Verification

- [ ] '  a   b  ' becomes 'a b'
- [ ] Removing blank lines leaves none
- [ ] Non-breaking spaces become normal spaces