Read a programmer's monologue below and answer the question. Recently, I had the opportunity to get involved in an exciting project where I programmed an interactive tool with a user-friendly interface, replicating the functionality of a traditional arithmetic device. To accomplish this, I utilized a combination of JavaScript, HTML, and CSS to develop the foundation of the program. I wrote code for various functions and operators, such as addition, subtraction, multiplication, and division, enabling users to perform calculations easily. I wrote code to replicate the movement of beads along rods to represent numbers. By applying JavaScript's event listeners and DOM manipulation, I ensured a seamless user experience, allowing users to input numbers and interac with the virtual device. The CSS styling brought visual appeal to the interface, enhancing its usability and clarity. Overall, I'm thrilled with the outcome of this project and confident that the implemented code will provide users with an engaging and intuitive online experience. What online tool did the programmer develop?