Zero-G in the Chemical Sandbox (Settings > Gravity). Nothing falls — liquids ball up, powders drift, smoke spreads.
3D Aerodynamics — a wind tunnel you build inside and orbit. Live drag and lift.
Menu music, with a toggle on the menu.
3D Sandbox: water settles level, one click places one block, building in mid-air works, and explosions.
Still working on unifying the UI and the stutter in explosions.