macOS
Steady
A fixed visual reference on top of your game, so your eyes always have something that isn't moving to hold on to.
What it does
When the 3D world rushes past but the frame around it stays perfectly still, the mismatch that causes motion sickness gets a lot smaller. Steady draws a reference frame, a crosshair and an optional clock over whatever you're playing.
It never steals your mouse or keyboard, needs no Accessibility or Screen Recording permission, and collects nothing.