Game Over

Crooked Calculator

We asked our smart intern to create a special calculator with a cool design and unique buttons for a client. He did an amazing job! But here's the twist: we, being a bit greedy, planned to fire him after the project (we're still trying to find out who told him). Our clever intern found out about our plan, but he still finished the calculator. Now, it acts really weird!
While we find another intern to fix this, an you help the client to do some calculations?