I was looking at this a few weeks ago then forgot about it. Pity its over as it was a decent graphics package.

A very quick rundown of what’s included in the Escape Motions Humble Bundle…

Amberlight 2 is a bit hard to explain… it uses math to generate line patterns that are influenced by attractive fields. You set a large number of variables using sliders etc., then move and adjust the strength patterns of 1 or more fields [the default is 4], set the render quality [e.g. for screen or print], and let it do its thing. There’s also a key-frameable timeline so you can create animations.
escapemotions[.]com/products/amberlight/

Inspirit is an app that creates fractal-looking line drawings that continue to grow as your PC or laptop does the necessary number crunching. You influence what the drawing looks like by drawing on the canvas using one of a few brushes.
escapemotions[.]com/products/inspirit/

Rebelle 3 is a typical painting app, with some nice tricks for watercolors & tracing.
escapemotions[.]com/products/rebelle/

Flame Painter 4 is a particle system painting app. en.wikipedia[.]org/wiki/Particle_system . The extended version of Photoshop years back had particle system brushes available, IF I remember correctly, but has since dropped them. Corel ParticleShop is the only other current app, or rather plug-in, that I’m aware of. painterartist[.]com/en/product/particleshop/?hptrack=mmptr#undefined . It’s easier to use, and as a plug-in you can use it while working on something like a photo – you import your image into Flame Painter, painting on another layer – but unlike Flame Painter, Corel tries to make their money selling add-on brush packs.
escapemotions[.]com/products/flamepainter/

humblebundle[.]com/software/natural-digital-painting-kit-software?hmb_source=navbar&hmb_medium=product_tile&hmb_campaign=tile_index_7

This is a graphics software bundle built around Flame Painter 4 at a good price. Like Corel Painter & the Twisted Brush apps, you should use a graphics tablet & stylus [they start ~$40 @ Amazon], or a touchscreen with stylus support to take full advantage of the apps.