Really nice take on the sliding tiles mechanic - there's a lot of potential for additional mechanics here, e.g. lining up enemies for combo strikes, placing the enemies/heroes next to environment tiles that confer advantages during attacks etc.
It feels like it maybe it needs some limit on the number of moves per level to reward optimum play.
It also felt like there should be more obvious feedback to my actions - often I was left wondering what the outcome had been when I selected a tile option or opened a chest.