Map fix.
Soulstone concept is easy: just remove the bottommost block from any row of the playfield. It will be your color. Once you have selected a color you have to make a set of three of the same color. When you have made a match-3, your color resets and you can pick a new color.
While the base concept is easy, every stage introduces a new affix (modifier) which makes your life harder. Every stage starts with only one affix, but during your progress more will be added. The last stage is an absolute nightmare, where even at the beginning you have to face against more than one affix.
All stages have an easy map to solve as a tutorial in the Tutorial section to get familiar with the affix.