Make the background a darker gray
Move the IDs to the top right of each box

Digestible version:
New problems can't be created
where problems would be
when there are no problems

When clicking on the line to add a problem, a menu should appear, allowing you to choose an essential problem or a nonessential problem
There should be boolean in each problem called "essential"
Essential problems should be on the left of the line, and nonessential should go on the left

When zoomed into a problem, that problem's text should be at the bottom left (regardless of scrolling).
The chosen solution's text should be at the top left (also regardless of scrolling).

The README should say:
A system to display problems graphically. Problems and solutions are represented as boxes, which can be infinitely nested. This allows problems to consist of a set of sub problems. Also, some sub-problems need be completed to solve the problem, while some don't. Solving all the required sub-problems represents doing the minimum, while also doing the nonessential represents anything above the minimum.

There should be some default text in the boxes - "no solution" for the solution, and "lorem ipsum" for the problem.
Also, there should be some way to change the text.

Create a method to generate doubles in a range, and plug that into the "new Color(" part of the niceColor method.

Click on the green part of a solution expands the section vertically to show the other possible solutions
Add a system to add new solutions to a problem
Add the # of solutions available to the top left of the green box

Have a randomly colored (hopefully a random bright color) stripe on the bottom of the window when zoomed in, and at the bottom of the problem when zoomed out

Clicking on red part of VisualProblemSolution box zooms into the red and shows the inner ProblemLine

The format will look like this:

*1
*1.1
-1.2
-1.2.1
-2
-2.1

-2.1.1

A * before an item means that it is essential
A - before an item means that it is nonessential
Tabs will be used for spacing