function checkCSyntax(code) {
    let errors = [];
    let lines = code.split("\n");
    let openBraces = 0;

    if (!code.match(/^\s*#include\s+<stdio\.h>\s*$/m)) {
        errors.push("Error: Missing or incorrect #include directive.");
    }

    if (!code.match(/int\s+main\s*\(.*\)\s*\{/)) {
        errors.push("Error: Missing main() function.");
    }

    if (!code.match(/return\s+0\s*;/)) {
        errors.push("Error: Missing 'return 0;' in main().");
    }

    let keywords = ["if", "else", "while", "for", "return", "int", "char", "float", "double", "void"];
    let variableDeclarationRegex = /^\s*(int|char|float|double)\s+[a-zA-Z_][a-zA-Z0-9_]*\s*(=\s*[^;]+)?\s*;/;
    let functionCallRegex = /^\s*[a-zA-Z_][a-zA-Z0-9_]*\s*\(.*\)\s*;/;
    let operatorRegex = /^\s*[a-zA-Z_][a-zA-Z0-9_]*\s*(\+\+|--|\+=|-=|\*=|\/=|%=)?\s*;/;
    let controlFlowRegex = /^\s*(if|while|for)\s*\(.*\)\s*\{/;

    for (let i = 0; i < lines.length; i++) {
        let line = lines[i].trim();
        if (!line) continue;

        if (line.includes("{")) openBraces++;
        if (line.includes("}")) openBraces--;

        let words = line.split(/\s+/);
        for (let word of words) {
            if (keywords.includes(word)) continue;
            if (word.match(/^(if|else|while|for|return)$/i)) {
                errors.push(`Error on line ${i + 1}: Misspelled keyword '${word}'. Did you mean '${word.toLowerCase()}'?`);
            }
        }

        if (variableDeclarationRegex.test(line)) {
            continue;
        }

        if (functionCallRegex.test(line)) {
            continue;
        }

        if (line.match(/[a-zA-Z_][a-zA-Z0-9_]*\s*-+\s*;/)) {
            let incorrectOperator = line.match(/[a-zA-Z_][a-zA-Z0-9_]*\s*(-+)\s*;/)[1];
            if (incorrectOperator !== "--") {
                errors.push(`Error on line ${i + 1}: Incorrect operator '${line.trim()}'. Did you mean '${line.trim().replace(/-+;/, "--;")}'?`);
            }
        }

        if (operatorRegex.test(line)) {
            continue;
        }

        if (controlFlowRegex.test(line)) {
            continue;
        }

        if (!line.endsWith(";") && !line.includes("{") && !line.includes("}") && !line.startsWith("#")) {
            errors.push(`Error on line ${i + 1}: Missing semicolon.`);
        }
    }

    if (openBraces !== 0) {
        errors.push("Error: Mismatched braces `{}`.");
    }

    return errors.length ? errors : ["Syntax is correct!"];
}