Mainframe: Symbolic Calculator

This calculator is a funny little app that is great at repeating the same calculation over and over with different numbers or variables. You have to get used to entering formulas are unintuitive to create using a graphical representation. But then every part of the formula is editable, like the numbers and operations, and you can get a lot of math done in a really short time!

There's no tutorial, but here are some tricks:

- Empty nodes will automatically appear when you assign an operation, so the easiest way to create formulas is to assign an operation (addition, subtraction, function, etc) and then assign a number, or a sub-operation.
- Tap "+" to add a new node, or you can drag from that button, to place the new node wherever you want it. You'll have to do this if you want to use variables (drag out an "x=" node).
- Drag from an "unattached" node to an operation to add that node to another operation's tree.
- You can use long presses on nodes to move sections of the tree around.
- You can have multiple formulas on-screen at the same time. Tap on any node on the tree to have it become the "current" operation.
- Shake the app to have your formulas arranged in a row, or press the "zoom" button to see all of your work, and tap in the place you want to edit.

Sorry that "multiplication" (×) and "x" look so similar. I'll try to address this in a future update. In the meantime, use "y" or "z" for more readable variables.

This app is open-source! Go to https://github.com/colinta/Mainframe to browse the code, open issues, or request features. I built this app on top of SpriteKit, using code from a game that I'm building.