The Betz module used to draw one number and a stream tube. Now there's a lattice Boltzmann solver running underneath it - 128,000 cells by default, up to 2.8 million if you want to make your machine work - with the rotor modelled as an actuator line: every blade cut into twelve elements, each one reading the local wind, working out its angle of attack, and pushing the reaction back into the air. The wake you see is what that reaction does. None of it is drawn by hand.
What you can change while it runs: wind speed, rotor radius, blade count, chord, taper, blade pitch, the tip-speed ratio it's running at and - separately - the one its blades were twisted for. Streamlines can be thin lines or wide ribbons. Grid size and compute backend (Auto, CPU, CUDA, OpenCL) are yours to pick.
The panel now prints Reynolds, Mach and blockage beside Cp, and that matters more than it sounds. The relaxation time is fixed, so a finer grid isn't the same flow resolved better - it's a higher Reynolds number: 37 on the smallest tunnel, 132 on the largest. The old caption implied otherwise. Comparing Cp across grid sizes compares different flows, and the module now says so instead of letting you assume.
Some things I got wrong along the way and fixed: blades were always drawn 120 degrees apart, so setting five blades still showed three (the physics had it right, the drawing didn't); the blade you saw tapered while the one in the equations didn't; the rotor swept straight through its own tower; the wind slider moved the numbers but not the flow.
Cloth - real fabric on the sheet, a different weave per material, mapped to the cloth's own coordinates so the pattern moves with the folds instead of sliding across them. Drape it over the crate and the crate's edges no longer show through. Tearing follows the material now, and landing on something no longer rips the sheet.
Demolition - courses end in half bricks the way a bricklayer ends them, so every brick is fully carried instead of the end one standing on half its neighbour.
Casimir - three visual layers were written, never switched on, and had been dark since release: the bloom, the sheets of light under the mode curves, and the vacuum sparkle that shows the mode imbalance instead of asserting it.
Physics engine - fast objects no longer sink into what they hit. A ball thrown at 12 m/s used to bury itself a quarter of its diameter before the solver noticed; contacts are now found before the surfaces touch. Bricks stopped looking like sponges.
Wave optics - the live field measured its screen inside the absorbing boundary, so a single slit showed twelve sharp maxima where physics gives one lobe. Now it gives one.
Geometric optics - for a mirror, the third construction ray is chosen rather than assumed; it used to be drawn passing straight through the mirror when it missed the surface.
Gears - the worm's lead angle carried a stray pi. The self-locking verdict was wrong for twenty of the thirty-six slider combinations, always in the same direction.
Interface - you can now type an exact value into any slider instead of aiming for it, and there's a searchable list of all 132 modules beside the carousel, filtered by field, with keyboard navigation. Both were asked for in reviews on release day.