Rotate/tilt: left-click drag (or one-finger drag on touch).
Zoom: scroll wheel (or pinch on touch).
Pan: right-click drag (or two-finger drag on touch).
Focus a body: double-click it (or long-press on touch) to fly to and follow it, or pick it from the Menu. Double-click the focused body again to return to wherever the camera was before. ⌂ Home returns to the full-system view.
Menu: a jump-to list of everything in the sim -- asteroids/dwarf planets/comets start collapsed, click their group name to reveal them.
True Scale: toggles planet sizes between exaggerated (the default, so they're actually visible) and their real size relative to the Sun -- most shrink to sub-pixel dots, which is the real scale of the solar system.
Time
Starts at real time (1 second per second), shown in your own local time zone -- not UTC.
Faster/Slower step through simulation speeds; Pause stops it.
The clock shows seconds at real time, and just hours/minutes at any faster speed (seconds would just be flicker there).
The date field shows the simulation's current date and doubles as a jump-to-date control: click it to open the calendar and pick a date to move the simulation there directly, past or future -- doesn't change the play/pause state or speed. Reset jumps straight back to right now.
Star drift: nearby stars quietly drift as the clock moves, extrapolated from their real proper motion and radial velocity (up to ±100,000 years from today) -- a linear approximation, not a real orbit simulation, so treat large jumps as illustrative rather than precise.
This list is kept up by hand and may lag behind the newest features for a bit.