the mechanic is interesting, the art is great (although the floor and walls have way too much aliasing) and unique, and i agree with the comments that the timer sometimes adds too much waiting,
it would have fit the story better if the timer itself turned to stone instead of turning red.
i think the "swap characters every X seconds" mechanic would work better if the game focused more on combat and you had to defend your petrified characters from enemies (as you'd now be constantly playing with your active character and literally never had the opportunity to just wait for a specific character)