<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Calculator</title> </head> <body> <header> <h1>ViaRézo Calculator</h1> </header> <div> <form action="/" method="get"> {% if expression %} <input type="text" name="expression" placeholder="12 / 2 + 6 * 8" value="{{ expression }}"> {% else %} <input type="text" name="expression" placeholder="12 / 2 + 6 * 8"> {% endif %} <button type="submit">Calculate</button> </form> {% if result %} <p>Result: {{ result }}</p> {% endif %} </div> </body> </html