Every knob here is read while the engine runs — nothing is baked, so a slider moves the picture under your hand.
Click the picture to stop it, and again to let it
go — or use the button. Stopping it really does stop it: the engine
takes its time from the clock, so the pause holds the clock too and it
picks up where it left off rather than jumping forward. Once it is
stopped, move over a mark to have it named and click it to change what
governs it —
that part needs the engine page to carry a pick pass
(tools/engine_pick.py); without one, a second click simply
starts it again.
The four colour controls at the top of the panel are a grade applied in this page, over the finished picture — the engine composites everything onto one canvas and has no saturation of its own. Everything below them is the engine's, and an exported file keeps the two apart.
The engine reads every one of these while it runs —
nothing is baked, so a slider moves the picture under your hand and there is
nothing to rebuild. 34 engine knobs, 23 elements that can be switched
off, and 6 that can be given an ink. Values are read straight out of
engine.js, so a resting slider is what the engine is actually
using. Be patient with it: elements are rationed and
SOLAR in particular can take a couple of minutes to appear.