<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Dark Code Previewer with Enhanced Compiler</title>
    <style>
        /* Reset some default styles */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        html, body {
            height: 100%;
        }

        body {
            background-color: #1e1e1e;
            color: #cccccc;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            display: flex;
            flex-direction: column;
        }

        header {
            background-color: #252526;
            padding: 15px 20px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            font-size: 1.5rem;
            font-weight: bold;
            border-bottom: 1px solid #333;
            position: relative;
        }

        /* Tabs for Mobile */
        .tabs {
            display: none; /* Hidden by default, shown on mobile */
        }

        .tabs button {
            background: none;
            border: none;
            color: #cccccc;
            padding: 10px 15px;
            cursor: pointer;
            font-size: 1rem;
            transition: background-color 0.3s;
        }

        .tabs button.active, .tabs button:hover {
            background-color: #3a3a3a;
            border-radius: 4px;
        }

        .container {
            flex: 1;
            display: flex;
            overflow: hidden;
        }

        .editor, .preview {
            flex: 1;
            padding: 20px;
            overflow: auto;
        }

        .editor {
            background-color: #1e1e1e;
            border-right: 1px solid #333;
            display: flex;
            flex-direction: column;
        }

        .editor textarea {
            width: 100%;
            height: 100%;
            background-color: #1e1e1e;
            color: #cccccc;
            border: none;
            resize: none;
            font-family: 'Courier New', Courier, monospace;
            font-size: 1rem;
            outline: none;
        }

        .error {
            color: #e74c3c;
            margin-top: 10px;
            font-size: 0.9rem;
            display: none;
        }

        .preview {
            background-color: #2d2d2d;
        }

        /* Scrollbar styling for WebKit */
        ::-webkit-scrollbar {
            width: 8px;
            height: 8px;
        }

        ::-webkit-scrollbar-track {
            background: #1e1e1e;
        }

        ::-webkit-scrollbar-thumb {
            background-color: #555;
            border-radius: 4px;
        }

        /* Responsive Design */
        @media (max-width: 768px) {
            .container {
                flex-direction: column;
            }
            .editor, .preview {
                flex: 1; /* Allow flex items to grow */
                display: none; /* Hide both by default */
                height: 100%; /* Ensure they can take full height when displayed */
            }
            .editor.active, .preview.active {
                display: flex;
                flex-direction: column;
            }
            .editor {
                border-right: none;
                border-bottom: 1px solid #333;
            }
            .tabs {
                display: flex;
            }
            .error {
                display: block;
            }
        }
    </style>
</head>
<body>
    <header>
        <div>Dark Code Previewer</div>
        <div class="tabs">
            <button id="tab-editor" class="active">Editor</button>
            <button id="tab-preview">Preview</button>
        </div>
    </header>
    <div class="container">
        <div class="editor active">
            <textarea id="code" placeholder="Type your custom code here...">
ul>li{Text}>ul>li{Sub text}
div>p[title="&index;"]{&index;. Hey}*5
style\{
div {
  color: red;
}
\}
script[type="text/javascript"]\{
alert('test');
\}
            </textarea>
            <div id="error-message" class="error"></div>
        </div>
        <div class="preview">
            <iframe id="previewFrame" srcdoc="" frameborder="0" style="width: 100%; height: 100%; background-color: transparent;"></iframe>
        </div>
    </div>

    <script>
        const textarea = document.getElementById('code');
        const previewFrame = document.getElementById('previewFrame');
        const errorMessage = document.getElementById('error-message');

        /**
         * Compiler Function:
         * Transforms custom syntax into standard HTML.
         * Supports:
         * - Tag definitions (e.g., h1{Hello})
         * - Attributes and IDs (e.g., button[role="button"]#click-me{Click Me})
         * - Nesting with '>' (e.g., div>p{Text})
         * - Sibling with '+' (e.g., h1{Title}+p{Subtitle})
         * - Repetition with '*' (e.g., p{&index;. Hey}*5)
         * - Embedding CSS and JS using style\{ ... \} and script[...] \{ ... \}
         */
        function compileToHTML(customCode) {
            const lines = customCode.split('\n');
            let html = '';
            let stack = [];
            let errors = [];
            let i = 0;
            const totalLines = lines.length;

            // State machine for block parsing
            let inBlock = false;
            let blockType = ''; // 'style' or 'script'
            let blockAttributes = '';
            let blockContent = '';
            let blockStartLine = 0;

            while (i < totalLines) {
                let line = lines[i].trim();

                // Skip empty lines
                if (line === '') {
                    i++;
                    continue;
                }

                if (inBlock) {
                    // Check for block end
                    if (line === '\\}') {
                        // Embed the block content
                        if (blockType === 'style' || blockType === 'script') {
                            html += `<${blockType}${blockAttributes}>\n${blockContent}</${blockType}>\n`;
                        } else {
                            // Treat as normal tag if block type is unknown
                            html += `<${blockType}${blockAttributes}>\n${blockContent}</${blockType}>\n`;
                        }
                        // Reset block state
                        inBlock = false;
                        blockType = '';
                        blockAttributes = '';
                        blockContent = '';
                        blockStartLine = 0;
                        i++;
                        continue;
                    } else {
                        // Append to block content
                        blockContent += line + '\n';
                        i++;
                        continue;
                    }
                }

                // Check for block start
                const blockStartMatch = line.match(/^(style|\w+)(\[[^\]]+\])?\\\\\{$/);

                // Corrected regex: need to escape backslash in JavaScript string
                const correctedBlockStartMatch = line.match(/^(style|\w+)(\[[^\]]+\])?\\\{$/);

                if (correctedBlockStartMatch) {
                    inBlock = true;
                    blockType = correctedBlockStartMatch[1];
                    blockAttributes = correctedBlockStartMatch[2] ? replaceIndexPlaceholders(correctedBlockStartMatch[2].slice(1, -1), 0) : '';
                    blockStartLine = i + 1; // For error reporting if block not closed
                    i++;
                    continue;
                }

                // Handle sibling elements using '+'
                const siblingTokens = splitRespectingBlocks(line, '+');
                siblingTokens.forEach(token => {
                    // Handle nesting with '>'
                    const nestingTokens = splitRespectingBlocks(token, '>');
                    let currentParentTags = [...stack]; // Clone the current stack for nesting

                    nestingTokens.forEach((nestedToken, index) => {
                        nestedToken = nestedToken.trim();
                        const isLast = index === nestingTokens.length - 1;

                        if (nestedToken === '') {
                            // Skip empty tokens to prevent errors
                            return;
                        }

                        try {
                            const { tag, attributes, id, content, repeat } = parseElement(nestedToken, i + 1);

                            let attrString = '';
                            if (attributes) attrString += attributes;
                            if (id) attrString += ` id="${id}"`;

                            if (repeat > 1) {
                                for (let j = 1; j <= repeat; j++) {
                                    // Replace &index; in content
                                    let finalContent = replaceIndexPlaceholders(content, j);

                                    // Replace &index; in attributes and id
                                    let finalAttributes = replaceIndexPlaceholders(attributes, j);
                                    let finalId = replaceIndexPlaceholders(id, j);

                                    let finalAttrString = '';
                                    if (finalAttributes) finalAttrString += finalAttributes;
                                    if (finalId) finalAttrString += ` id="${finalId}"`;

                                    if (isLast) {
                                        html += `<${tag}${finalAttrString}>${finalContent}</${tag}>\n`;
                                    } else {
                                        html += `<${tag}${finalAttrString}>\n`;
                                        stack.push(tag);
                                    }
                                }
                            } else {
                                if (isLast) {
                                    if (content) {
                                        let finalContent = replaceIndexPlaceholders(content, 0);
                                        html += `<${tag}${attrString}>${finalContent}</${tag}>\n`;
                                    } else {
                                        html += `<${tag}${attrString}></${tag}>\n`;
                                    }
                                } else {
                                    html += `<${tag}${attrString}>\n`;
                                    stack.push(tag);
                                }
                            }
                        } catch (err) {
                            errors.push(`Line ${err.line}: ${err.message}`);
                        }
                    });
                });

                i++;
            }

            // After processing all lines, check if any blocks are still open
            if (inBlock) {
                errors.push(`Block starting at line ${blockStartLine} for <${blockType}> not closed with '\\}'.`);
            }

            // Close any remaining open tags
            while (stack.length > 0) {
                const tag = stack.pop();
                html += `</${tag}>\n`;
            }

            if (errors.length > 0) {
                return { html: '', errors };
            }

            return { html, errors: [] };
        }

        /**
         * Splits a string by a delimiter but ignores delimiters inside quotes or blocks.
         * @param {string} str - The string to split.
         * @param {string} delimiter - The delimiter to split by.
         * @returns {Array} - Array of split tokens.
         */
        function splitRespectingBlocks(str, delimiter) {
            const tokens = [];
            let current = '';
            let inQuotes = false;
            let quoteChar = '';
            let escape = false;

            for (let char of str) {
                if (escape) {
                    current += char;
                    escape = false;
                    continue;
                }

                if (char === '\\') {
                    current += char;
                    escape = true;
                    continue;
                }

                if ((char === '"' || char === "'") && !inQuotes) {
                    inQuotes = true;
                    quoteChar = char;
                    current += char;
                    continue;
                }

                if (char === quoteChar && inQuotes) {
                    inQuotes = false;
                    quoteChar = '';
                    current += char;
                    continue;
                }

                if (!inQuotes && char === delimiter) {
                    tokens.push(current);
                    current = '';
                    continue;
                }

                current += char;
            }

            if (current !== '') {
                tokens.push(current);
            }

            return tokens;
        }

        /**
         * Replaces all instances of &index; with the provided index number.
         * If index is 0, it leaves the placeholder as is (useful for non-repetitive cases).
         * @param {string} str - The string to process.
         * @param {number} index - The index to replace &index; with.
         * @returns {string} - The processed string.
         */
        function replaceIndexPlaceholders(str, index) {
            if (index > 0) {
                return str.replace(/&index;/g, index);
            }
            return str;
        }

        /**
         * Parses an element definition from the custom syntax.
         * @param {string} token - A token from the custom code.
         * @param {number} lineNumber - The line number for error reporting.
         * @returns {Object} - Parsed element details.
         */
        function parseElement(token, lineNumber) {
            // Regex to match the element definition with optional attributes, ID, content, and repetition
            // Example matches:
            // div>p[title="button"]#click-me{Click Me}*5
            const regex = /^(\w+)(\[[^\]]+\])?(#[\w\-]+)?(\{[^}]*\})?(\*\d+)?$/;
            const match = token.match(regex);

            if (!match) {
                throw { message: `Invalid syntax near "${token}".`, line: lineNumber };
            }

            const [ , tag, attrs, id, content, repeat ] = match;
            let attributes = '';

            if (attrs) {
                // Remove the surrounding brackets
                const attrContent = attrs.slice(1, -1);
                // Replace &index; if any
                const replacedAttrContent = replaceIndexPlaceholders(attrContent, 0);
                // Validate attribute format
                const attrRegex = /(\w+)="([^"]+)"/g;
                let attrMatch;
                while ((attrMatch = attrRegex.exec(replacedAttrContent)) !== null) {
                    const [ , attrName, attrValue ] = attrMatch;
                    attributes += ` ${attrName}="${attrValue}"`;
                }

                // Check if attributes are correctly formatted
                const validAttrFormat = /^[\w\s-]+="[^"]+"$/.test(replacedAttrContent.replace(attrRegex, '').trim()) === false;
                // If attributes are present but no valid attributes were parsed
                if (attributes.trim() === '' && attrContent.trim() !== '') {
                    throw { message: `Attributes must be in the format key="value".`, line: lineNumber };
                }
            }

            const element = {
                tag: tag,
                attributes: attributes,
                id: id ? id.slice(1) : '', // Remove '#' from id
                content: content ? content.slice(1, -1) : '',
                repeat: repeat ? parseInt(repeat.slice(1)) : 1
            };

            return element;
        }

        /**
         * Updates the preview iframe based on the compiled HTML.
         */
        function updatePreview() {
            const customCode = textarea.value;
            let compilationResult;
            try {
                compilationResult = compileToHTML(customCode);
            } catch (error) {
                compilationResult = { html: '', errors: [`Unexpected error: ${error.message}`] };
            }

            const { html, errors } = compilationResult;

            if (errors && errors.length > 0) {
                errorMessage.textContent = errors.join(' | ');
                errorMessage.style.display = 'block';
                previewFrame.srcdoc = ''; // Clear preview if there are errors
            } else {
                errorMessage.textContent = '';
                errorMessage.style.display = 'none';
                // Wrap with basic HTML structure and custom dark theme
                const fullHTML = `
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Preview</title>
    <style>
        body {
            background-color: #1e1e1e;
            color: #cccccc;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            padding: 20px;
        }
        h1, h2, h3, h4, h5, h6 {
            color: #ffffff;
        }
        p {
            color: #dcdcdc;
            margin-bottom: 10px;
        }
        button {
            padding: 10px 20px;
            background-color: #3498db;
            color: #fff;
            border: none;
            cursor: pointer;
            border-radius: 4px;
            margin-top: 10px;
        }
        button:hover {
            background-color: #2980b9;
        }
        a {
            color: #9b59b6;
        }
        a:hover {
            color: #8e44ad;
        }
        /* Additional styles for various elements */
        ul {
            list-style-type: disc;
            padding-left: 20px;
            margin-bottom: 10px;
        }
        li {
            margin-bottom: 5px;
        }
        input, textarea {
            background-color: #333333;
            color: #ffffff;
            border: 1px solid #555555;
            padding: 8px;
            border-radius: 4px;
            margin-top: 5px;
        }
        input:focus, textarea:focus {
            border-color: #3498db;
            outline: none;
        }
        table {
            width: 100%;
            border-collapse: collapse;
            margin-top: 10px;
        }
        th, td {
            border: 1px solid #555555;
            padding: 8px;
            text-align: left;
        }
        th {
            background-color: #444444;
        }
        tr:nth-child(even) {
            background-color: #2d2d2d;
        }
        /* Embedded Styles */
        ${extractEmbeddedStyles(html)}
    </style>
</head>
<body>
${html}
</body>
</html>`;
                previewFrame.srcdoc = fullHTML;
            }
        }

        /**
         * Extracts embedded <style> blocks from the generated HTML to include in the preview's head.
         * @param {string} html - The generated HTML content.
         * @returns {string} - Extracted CSS from <style> blocks.
         */
        function extractEmbeddedStyles(html) {
            const styleRegex = /<style[^>]*>([\s\S]*?)<\/style>/gi;
            let styles = '';
            let match;
            while ((match = styleRegex.exec(html)) !== null) {
                styles += match[1] + '\n';
            }
            return styles;
        }

        // Initialize preview
        updatePreview();

        // Update preview on input with a slight debounce
        let timeout;
        textarea.addEventListener('input', () => {
            clearTimeout(timeout);
            timeout = setTimeout(updatePreview, 300);
        });

        // Tab functionality for mobile
        const tabEditor = document.getElementById('tab-editor');
        const tabPreview = document.getElementById('tab-preview');
        const editor = document.querySelector('.editor');
        const preview = document.querySelector('.preview');

        function activateTab(tab) {
            if (tab === 'editor') {
                tabEditor.classList.add('active');
                tabPreview.classList.remove('active');
                editor.classList.add('active');
                preview.classList.remove('active');
            } else if (tab === 'preview') {
                tabPreview.classList.add('active');
                tabEditor.classList.remove('active');
                preview.classList.add('active');
                editor.classList.remove('active');
            }
        }

        tabEditor.addEventListener('click', () => activateTab('editor'));
        tabPreview.addEventListener('click', () => activateTab('preview'));
    </script>
</body>
</html>

---

Let's give this a creative name together