Horizontal scrolling problem with shell and other shell/editor layout ideas

If you call `input("Reasonable length prompt: ")` then the shell scrolls to the right, hiding the content on the left. The reason for this is a bit of CSS `width: calc(100% - 2.5em)` on a div wrapping the `` tag where the user types into the shell. But removing that leaves the input element short so that if you enter a long line of code it doesn't show the full thing. I don't know what a good solution is. The side-scrolling issue was noticed [here](https://www.spysafe.com.au/wc-code-nim.html) which is sad because they say great things about futurecoder otherwise.

There are other ways in which the layout of the course/IDE could be improved which wouldn't really solve this issue but might help and also improve the site in other ways. These are just loosely related and can be done in isolation.

- The borders between editor and shell (in both course and IDE mode) and between the editor/shell and course could have 'handles' which resize the sections when dragged, so that the editor or shell can be bigger when I want.
- In IDE mode, there could be a button to switch layout, so the editor and shell would have the full width of the screen and occupy the top and bottom halves instead of left and right.