On right side you can tweak the settings.
W/A/S/D/SHIFT/SPACE to move and mouse to look around.
With scroll you can adjust camera speed.
You are gravitationally bound to the closest planet. In gravity tab you can manually attach to other planet.
If you're close enough to a planet, you will be pulled towards it and camera would be rotated as if you were standing on its surface.
! Gravity simulation can be very UNSTABLE (i have focused on shader aspect). !