Instead of having a single GUI checkbox for "Always Hide Mouse Cursor",
I have instead opted to use radio buttons so the user can swap between
different states of mouse visibility. "Movement" is the default
behavior, "Never" will hide the mouse cursor the entire time the game is
running, and "Always" will keep the mouse cursor always visible.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
