Bubble Sorting

Colored balls sit jumbled across a row of vials, and you pour them between containers until each vial holds just one color. You can only move a ball onto a matching color or an empty vial, and that single constraint is what the whole puzzle rests on. More vials arrive as you progress, and later levels add extra rules on top of the basic sorting, so a pour that looked safe early can box you in a few moves later.