Actually, these are blurred circles. Apparent when you set the "fuzziness" slider to zero.

Metaballs are different. They are essentially a visualization of electric or gravitational fields. For the traditional formula in 2D, each pixel is colored based on the weighed sum of the inverses of the distances to the center of each "ball".

Yep, metaballs. I'm planning on upgrading to the "double density relaxation" algorithm to make it more lava-y. I've never done that before, and the algorithm is pretty complex...

Here's a good example if you're interested. https://peeke.nl/simulating-blobs-of-fluid