🪐 Planetarium Star Dome (2D)

This 2D companion replaces the rotating decorative starfield of the 3D dome with a real sky: roughly 40 bright stars across 14 recognizable constellations, each carried at its true right-ascension/declination, projected onto the dome with the same equatorial-to-horizontal transform planetariums and star-chart software use. Drag the latitude slider toward the poles and whole constellations stop rising or setting; drag the date slider through the year and the Sun's ecliptic motion shifts which stars are up at midnight; drag time-of-night and the sky visibly turns — because it is being recomputed from spherical trigonometry every frame, not a canned animation.