Galactic Rotation Curve (2D)

This 2D companion drives the same disk-plus-NFW-halo physics as the 3D version through a plain canvas view built for reading the physics rather than orbiting a scene: a side panel exposes the dark matter fraction, total galaxy mass, halo scale radius and a visual orbit-speed control, a top-down star field colours each orbiting star by its instantaneous speed (blue for slow, red for fast), and a live V(r) plot traces the dashed Keplerian curve that visible mass alone would produce against the solid, stubbornly flat curve the NFW halo actually produces — making Vera Rubin's discovery directly visible instead of implied.