Advanced AI Prompt for Metaball Fluid Dynamics Shaders

Act as a Fluid Dynamics Programmer. Develop an intense GLSL fragment shader dedicated to rendering exactly [BALL_COUNT] interactive metaballs (liquid blobs) that magnetically react to the user's mouse coordinates. Construct the underlying scalar field using the inverse-square law (`1.0 / distance`) summed simultaneously across all floating point coordinates. Force the field through a sharp, rigid [THRESHOLD] `step()` function to create solid, hard-edged cell membranes, or a `smoothstep()` for gooey, blending edges. Inject a localized [COLOR_GLOW] radial gradient into the absolute center of each mass, while programming their autonomous, bouncing trajectory using a [VELOCITY] vector. Aggressively optimize the nested `for` loop to guarantee a locked 60FPS on mobile GPUs by completely eliminating highly expensive `sqrt` distance operations in favor of squared distance checks.