I would like to lock the mouse on a program I am making, but I'm not sure if it is against the guidelines.

The guidelines say "To ensure that the ProcessingJS programs you create on Khan Academy will continue working in the future, they should not use functionalities intentionally disabled for reasons of security, privacy, or user experience. Generally, that means that JS programs should not be accessing `externals` or the `DOM` in some way."

But locking the mouse doesn't use functionality that breach security or privacy, and being able to lock it would enhance user experience, and I have seen several programs that lock the mouse that have not been hidden.