<paper-code-mirror>
HTML Mode
<paper-code-mirror title="HTML">
            <template>
                <div class="container">
                    <div class="header">
                        <a href="http://google.com" target="_blank">Hello</a>
                    </div>
                </div>
            </template>
</paper-code-mirror>
            
JavaScript Mode, Night Theme, With Line Numbers
<paper-code-mirror theme="night" line-numbers title="JavaScript" mode="javascript">
    <template>
        var length = 16;                               // Number
        var lastName = "Johnson";                      // String
        var cars = ["Saab", "Volvo", "BMW"];           // Array
        var x = {firstName:"John", lastName:"Doe"};    // Object
    </template>
</paper-code-mirror>
            
SQL Mode, Midnight Theme, With Line Numbers
<paper-code-mirror line-numbers theme="midnight" title="SQL" mode="sql">
    <template>
        SELECT 'column_name','column_name' FROM 'table_name';
    </template>
</paper-code-mirror>