Calcul Watch

This is a prototype of the game that cannot be completed on time made for "Ludum Dare 60". The theme is "Old Tech".
The interpretation of this theme is "Using a Calculator Watch". Calculator watches used to be seen as modern, but now can be seen as old tech.
I plan on turning this prototype into somewhat of a rougelike game during the jam. Might update the game on Saturday or Sunday. I was not able to compose music due to time constraints, but the game may soon have them.
HOW TO PLAY
Use the arrow keys to select buttons, use the Z key to select it.
Your goal is to try to make the equation correct by using the buttons. Use the green check button to submit the answer, Use the red X button to reset this equation.

As for what can be done right now, it would be great to add a visual guide to the controls in the page description, because at first I thought the game just wasn't working.