Cool puzzle game, it's fairly intuitive aside from the stacking. Visuals could be improved, I would especially like the way the current colors are displayed on the character, it's a bit boring right now. The fact that you used colors and shapes is a cool bit of accessibility. One thing that may help with making the stacking mechanic clear might be to have the visual that appears in the top left appear large and in the middle of the screen, and then shrinks back down into the top left corner again.