Welcome!

Here are some suggestions for improvements:

• Add more functions
  • https://en.wikipedia.org/wiki/Elementary_function all the functions here like:
    • Exponential functions
    • Logarithms
    • Trigonometric functions
    • Inverse trigonometric functions
    • Hyperbolic functions
    • Inverse hyperbolic functions
    • Subtraction/division
• Simplify Expressions
• Handle parenthesis, both for input and output

Adding your own solution

Please make a pull request adding your code to a folder ./submitted_solutions/YOUR_GITHUB_NAME/

I'd love to see what you end up coming up with!