水球星球

Reuse an MLS-MPM fluid solver but compute gravity per particle as a vector toward the planet's center instead of a constant down vector. Add a solid inner sphere as a boundary in the grid update step by zeroing the inward normal component of velocity inside it. Render with screen-space fluid techniques (depth splat, bilateral blur, normal reconstruction) plus a simple planet core shaded underneath. Let drags rotate the camera and inject an impulse into nearby grid cells.